EG Chance's Quake Bible

Introduction

Practice, Practice, Practice. The famous words of Champion Johnathan "Fatal1ty"
Wendel. We've all heard it before, and we all know how important it is to reaching
the highest levels of play, but what about those guys who practice all day every
day and seem to never improve? I'm sure you know who I'm talking about. That
guy who's been playing for the last 4 years and in the 240 hours of game time
he's logged, since the Quake Live beta opened, has barely managed to etch out a
positive record. Well, this article intends to help those players - and any player
ready to patch up holes in their game that prevent them from reaching higher
levels of play. Unlike other articles, you won't find play by play instructions here.
Quake is about choices. From the second you spawn in, every single thing you do
matters. As we'll see more into this guide, even every single thing you think
about doing matters.

This article is structured around insight. Insights are the foundation for your
improvement; the building blocks of your game. They enable you to make the
right choices at the right times. Without them, you can't build a structure strong
enough to carry you into the next level. Remember that in every step forward
there is an often hidden insight holding it in place that you must find in order to
further establish it as your strength. Meaning, if you're playing great - there's a
reason why. You have to find that reason to retain that level of play. If you're
playing miserably, there's a reason why. You have find that reason and stamp it
out.

The following sections primarily contain insights to help you improve your game
on your own, this is the most important thing you can learn. You won't always
have someone to tell you how to play. Irregardless I cover a few key subjects that
should be your primary focus every time you play. Those two subjects are enemy
status and timing. We'll get to them a little later. For now, we need to understand
some principles to keep your head together.

Discipline. (Willing forward the strongest formula)

Create no waste. Discipline is probably the most difficult and synonymously
important strength of a competitor. Discipline is often what separates the
aforementioned soft practice junkies from the hardened veteran masters. The
practice junkie plays, and plays, and plays, but while he does so he'll be thinking
about doing his laundry. Or what about that new episode of Lost? A thousand
superfluous thoughts are floating through his head while he's drunkenly dropping
into the void like a bewildered klutz or missing the easy jump pad rail. Players like
Fatal1ty will tell you, even when you practice you need to focus 100 percent on
every game, the entire game. If you can keep this up for 8 hours a day you're
going to come out with some serious results. If you can do that, by the way, you
may have some kind of gift ;p. There are few people I know that can play more
than a couple hours without reaching "burn out." Don't concern yourself too much
with the quantity however, because the quality is what counts.

So discipline is largely about staying focused, and staying focused has a lot to do
with your emotional state. You can't be getting too angry, excited, or relaxed
when you need to be completing a crucial task like timing red armor or dodging
behind a pillar. An example of the kind of excitement that creates problems is
when that energetic excited feeling takes your mind out of the game. i.e. "I'm
doing so good! That shot was amazing! Wait.. what was the armor time again?"
Herein lies the difference between an amateur and an expert. The expert player
will simply move onto the next frag, perhaps increasing or maintaining the same
level of energy and readiness whenever necessary.

All that matters is that at the very least you're ready to accept and deal with the
current situation, rather than acting on your emotions regarding the current
situation. On the whole, emotional features like excitement will, by nature, lead
to what are called "leaks." Unintentional holes in your game that, despite knowing
what you should have done in a situation, you went ahead and did something
else. Leaks commonly arise from emotion, but they may also come in a more
dangerously subtle package; thoughts. Anytime you have thoughts floating
around that don't pertain to the game at hand you generate leaks. Disciplined
athletes have little to no leaks.

In order to prevent leaks you have to be aware of your current state of mind.
Keeping your mind clear of fog will allow you to take on any and all information
presented to you, and process it in an unbiased, no-nonsense fashion. With a
clear mind, you stay out of your own way and focus on the critical information
you need to make your next move. That is what strong discipline is about and
that is the core purpose of discipline.

Don't think of discipline as a strenuous exercise. A large part of it is making
yourself comfortable with giving it your all and ensuring you're ready to play
irregardless of what might have or could happen inside and outside of the game.
There is an "easy way" to attain a leak-free strong discipline without breaking
your routine down into thousands of meticulous details and then making yourself
remember them all when you need them. This leads us to our next insight.

Presence. (Remaining in the moment to maximize mental efficiency)

Presence is the state of mind (or no-mind) that has no past or future. Without
past and future, you are not wasting your brain cells/neurons on things that do
not currently exist and therefore hold no bearing on you as a player. You are
focused entirely on what is happening, and since what is happening is all there is,
it is therefore all that matters. This is an easy way "cut down" or lean up your
thoughts and become all killer, no filler. In my experience, you are may only
compete at your peak performance when you are committed fully to the present
moment. The ideal way to look at this is; there is no seperation between you and
what is. This "oneness" is commonly referred to by sports analysts as, "the zone."
Disciplined presence means we should be playing the entire game in the moment
as it emerges unto itself.

You don't need to "think" to strafe jump. You just do it, and the more you can
clear up the mental noise in your head while you play - the more your mind will
wrap around the task you're trying to accomplish. The task of discipline is greatly
simplified by just maintaining continual conscious presence. How is this achieved?
Focus on the task at hand, nothing more, nothing less - and not so much on the
task, but the totality of the moment.

Your mind should be like water, ready to adapt perfectly to fit any container.
Concentrate on what is happening, what the situation needs from you, don't think
it out in long-drawn inner dialogue - just be aware of it and allow it to come
through you. Give your mind the space and freedom to gather all the information
you need. Allow yourself to respond to the situation with relentless indifference,
clarity. Through this comes power. This is natural for a lot of athletes but will take
some practice in itself if you're not used to it. It seems like focusing on the "Now"
is common sense, but that all depends on how aware you are of your straying
thoughts and emotions. There's not much more that I can say about this, you
either get it or you don't. If you don't, just keep playing with a clear head and
always focus. Eventually you'll figure out how to find your "zone." When you do,
recognize the Presence and understand that it is an enormously beneficial ability
which can become absolutely pivitol to your success as a player.

Alright, so. Now we know we need discipline to continually bring our best forward
so we can call on our abilities at will, and we know how to stay in the moment so
we can be efficient with our mental resources. The line between beast and newbie
doesn't stop at staying focused and cognatively present the entire time, you have
to be focused on the right things. Now, what exactly are these "right things" I
keep mentioning, the "important stuff"? What should I concentrate on while I
play?

Opponent Awareness/Enemy Status. (Mastering the raw data.)

Whether you're playing Duel, Team Deathmatch, Clan Arena, Free for All, or even
Counter-Strike for that matter - your awareness of the enemies status is huge.
This is the part of the game that provides you with the information to make
almost all of your decisions useful. I come from a Duel background, so for the
most part I will explain this from a singular, one-player perspective rather than
the plural, team-oriented perspective, but the same nonetheless applies to either
mode.

Your opponent has XXX health and armor (at maximum totalling up to 400), he is
standing X,Y,Z on the map, with X weapons, and X ammo. The opponent is also
moving at XXX units per second. These variables are life and death in the arena.
The ability to contain this information accurately within your consciousness is the
apex of your game. I can't stress this enough because when it comes down to
winning or losing a frag - the most common thing a player does is --misread the
situation and--- mistake some other feature for the reason it happened.

For example: Player B goes through a doorway expecting Player A to have 25
health, when really Player A has 125 because he just got the mega health. When
Player B gets killed after landing a few beads of shaft he gets mad and blames his
aim for not doing enough damage. The anger itself is an issue, but we'll get to
that later. The misjudgment of enemy status is by a landslide the most common
mistake players make, and if not immediately corrected here it has the potential
to just domino.

Any time a gap occurs in our intellect we immediately fill it with the most easily
accessibly and most seemingly obvious reason, and if there is no obvious
reason... we invent one! Creating a solution to fill the gap works well on a short
term scale to alleviate a problem with the best solution we can come up with off
hand, but eventually if the player leaves it unchecked his game's foundation is
liable to become almost superstitious. Many times rather than filling the gaps with
a logical guess to what may have happened players fill it with any answer that
most conveniently protects their ego. Anger is likely indicative of the player trying
to defend his sense of strength that he feels he is losing by being punished.
Players that get stuck in ego will perpetually blame some inauspicious aspect of
the game, continue letting problems chain together by answering them
baselessly, and thus continue to be on the receiving end of the next fragger.

The only way out of this is being honest with yourself and accepting the reality of
the situation, which, I will tell you on the bright side is that you simply did not
accurately read the information you were given. Why is that on the bright side?
Because you no longer have your superstitions like "I just suck" to blame, you
have real, tangible reasoning to tell you what went wrong, and how exactly to
deal with it. We are all human, we all make mistakes. We need to remind
ourselves that these mistakes can either bear fruit, or drag us to hell, depending
on whether we accept our equality and subsequent mortality, or cling to ego and
think somehow we deserve better or worse without first understanding more. It's
the questions we can not answer that cause our suffering should we find
ourselves in a situation where we are struggling.

Once you have accurate awareness of the enemy's status, this is where the Art of
War comes in. (<3 Sun Tzu) Now you can constantly balance your status against
the enemy status, and move accordingly. If you have the advantage, you attack.
At the disadvantage, you wait for your opponent to make a mistake or you retreat
in order to gain more resources than your opponent.

What about when your back is against the wall and you can't retreat? You're out
of luck. The best way out of any sticky situation is to not get stuck there in the
first place. If you're already in this situation you're forced rely on a miracle shot,
opponent choke, luck, or some insight into your opponents fallibility to survive.
This is the last thing you want to do. Good players will attempt to force you into
this situation all game long. There's never a time when they want you to be
prepared.

You always hear about successful athletes and gamers "visualizing" their success.
I promise you they aren't visualizing having 2 health and hitting 5 consecutive
grenades for the win. They're seeing kills unfold realistically and effortlessly in
their minds eye. Studies have shown visualization helps immensely in improving
task completion. In fact, it's been shown that you can actually gain muscle by
merely thinking about lifting weights. Try and keep your opponent contained in
your minds eye throughout the game. And you don't just want to think about
where they are, you want to literally contain them by limiting how they can
expand around the map.

The majority of the learning curve in any game comes from getting yourself into
the right situations. The more experienced you are, the easier it becomes to
make useful choices using the discrepency between your enemies status and your
own, and the more meaningful every move you make becomes. I said it earlier
and I'll say it again. Quake is a game about choices. From the second you spawn
in, every single thing you do or even think about doing matters. Misinformed
decisions lead to death. If you can't figure out immediately why you just lost or
got fragged, go back and examine the replay afterwards. You need to understand
what happened. (Hopefully one day we'll have easy-access demos that display
enemy health, enemies through walls, and item times.)
Enemy status is key, but make sure you're always paying attention to your own
status (and your team if you're in a team mode). You might think you can take on
125 health joe newbie with his spawn shotty - but if you're not healthy enough
and he's in close ducking behind pillars he's gonna drop you like a brick. I'm
always suprising myself how often I go in to attack and look down and realize I've
got 150 armor but only 12 health. It's a given that any time enemy status is
considered, it should be weighed against your and your teammates statuses as
well.

The most difficult thing is gathering this information, and retaining it while
playing. Saying that it's difficult is misleading, however, because this again isn't a
stressful or demanding skill. It can be achieved with ease given time, discipline,
and continual conscious presence. The idea of difficulty is purely psychological
and arises when you resist your current situation or the "time" it takes to
accomplish your desired result.

Other insights reguarding enemy status can include player tendencies. If you've
played a person enough times, or even in your first time playing a guy you can
sometimes pick these up a few minutes in. You can use them to "get inside" your
opponents head, putting damage on them when they're not expecting it - or
taking the RA they always leave up when Mega spawns. Psychology can also play
a role here. If you know your opponent is fatigued, you may be at an advantage.
This isn't something you will want to learn to rely on, but it helps to be aware of it
so when they're feeling peppy next time - you can expect they won't be cutting
you the same slack.

So I know where he is, I know how much health he's got and I'm totally with it.
What else do I need to focus on? We'll discuss just that in the next part.

Resource Timing (Expanding and controlling your advantages)

Resources include items placed around the map that are designed to give you or
your opponent an advantage. In most modes these include weapons, armor,
health, quad, and other powerups. In Quake, it is essential that you time items to
the second. First and foremost you'll be weighing enemy status with your status,
but the ultimate goal of resource management is to effectively eliminate your
opponents ability to gain any significant advantage.

This means timing the most important items while simultaneously preventing
your opponent from getting them. This also means what items you can not time
you need to be mindful of as well. If you know they don't have the Lightning Gun
(LG) but you do, not only will you try to force mid-range fights where you have
the damage advantage, you will also want to prevent them from getting the LG so
you can continue control area's of the map that are best suited for its use. The
same goes for rockets (close range) and rail (long range). As you can see, enemy
status falls in to effect resource status, and vice versa.

In duel, the advantage of the Megahealth and Red Armor are so great that you
want to have each of them timed all game, every game. This is an area where a
lot of players faulter. You can play mindlessly all day long and garner enough
experience to eventually have a pretty solid lock on enemy status, but item
timing is a whole other beast. It takes planning, forethought, careful execution
and extreme intelligence. Experts say you need an IQ somewhere in the 140's at
least. Wait... really? No. Again - this isn't something that requires a lot of stress
or effort. Like everything else it just requires conscious present awareness.
Forethought itself only happens in the present moment. The future holds no
significance. Just because you're timing something does not mean you are
focusing on the future. All timing requires is presence and the ability to add. The
important thing to remember here is to time to the second.

What I often do is simply repeat ":16, :16, :16" in my head and if I have Mega
and RA timed I repeat the RA time too, ":16, :23, :16, :23..." Keep in mind that
its not necessary to time like this if you are good at remembering when it spawns
without it. I generally have trouble timing without repeating the numbers if I
haven't been playing in awhile or I'm distracted (either by physical external things
or just mental noise).

It may also help you to time them out loud. I recall sitting behind Paul "CZM"
Nelson and hearing him chant the spawn times for RA and MH like a quake item
conjurer after he said in the game prior he was having trouble timing. Sometimes
I'll get confused and mix up which items are spawning in which order, especially
when mega is spawning before RA (because mega usually spawns after RA). For
example I'll be repeating ":26, :30, :26, :30" in my head but the item I think is
going to spawn at :26 is actually spawning at :30 and vice versa, so it may be
helpful to remember to emphasise the next coming item in your head first and
foremost.
As we said before, in order to maximize any advantage you gain from picking up
a resource you must time it. Of course this will not be possible with every item,
not only because some items spawn in less than 5 seconds effectively rendering
timing them meaningless, but also because there are often 20+ items per map
and the average human being can only remember around 8 digits at a time.
So why is timing a weakness for so many? Well for starters, many players
experience heavy mental resistance to it, most often labeling it as a "less fun"
aspect of the game. Other people are trapped in the illusion that its too effortful,
and requires too much of their concentration or is beyond their intelligence.
General lack of discipline is, however, the biggest problem. Mental wandering
anyone? Too frustrated or impatient to remember the time? There's your lacking
discipline.

Item status, enemy status, and team status are an interconnected power struggle
where the exact respawn times play a critical role. Megahealth respawns at :XX,
red armor at :XX. You have XXX health+armor... You get the picture. Accuracy
within these categories takes time and determination to master. Along the way,
its a lot of fun. Brilliant plays start to emerge when both players become fully
aware of the enemy status and item times. It's a game with RTS style resource
management and Fighting game reflexes. The overlay of deception and
punctuality unfolds a dynamic and eternally interesting genre of E-Sport. Every
map has a unique architecture, powerup layout and weapon scheme. This sets
the stage for a vast set of gameplay meta-memes and personal meme's just
waiting to be uncovered.

Perhaps in the future I'll write an article laying out the specific meta-strategies
encountered on individual maps, but for now this marks the conclusion of the
"what to do/think about in-game" section. From here, there's a few other things
to consider pre-game and post-game.

Aim (The most overthought skill in Quake.)

If you were to ask the best aimer in the world how he aims so good he would
probably explain the process in a way that would leave you just as well off as if
he told you to tap your heals together and wish for good aim. Indeed, the concept
of "aiming well" is one place where things get a little foggy for us humans to
describe =]. We tend to try to quantify things in order to understand them and
aim is such a dynamic category we are stuck with a lack of general insight here.
But there are a few things that I think play a crucial role in aim.

1. Comfortablility. Firstly, you need to be comfortable with your environment. If
you're not used the height of your chair, size of the monitor, shape of your mouse
etc. you may have trouble aiming just because you'll be encumbered with
discomfort the whole game. Simple ^_^. Next you need a sensitivity you can
stand behind 100 percent. To do this, you need it to meet the demands of the
arena with absolute ease and comfort. This means setting it high enough for
those quick yet important placement shots, and having it low enough to maintain
a steady track.

Warmup is there purely to get a good comfortable feel for your setup and make
your mind comfortable with your sensitivity and the general handling of your
mouse again.

2. Concentration. I've said enough on this already. Presence directly equates to
amazing aim =]

3. Movement. Great movement kills two birds with one stone. You stand where
you need to be to simplify the shot(s) while synonymously avoiding enemy
attacks.

These are really the only three factors of any relevance that I can offer you when
it comes to aiming. A lot of people get borderline superstitious with their aim.
Some will nervously tweak mouse settings, sensitivities, visual configs like they
have obsessive compulsive disorder. Don't be that guy ;p.

Here's a few more tips to make sure you're on the right track.

Stop trying to predict the future. There's a lot of hype in being able to "read" your
opponent. Thats fine, but don't mistake "reading" them for predicting them. You
can not predict what a person will do. Trying to predict player movement in battle
will only lead to poor accuracy and frustration. What you can do is merely read
their movements and this'll be all you need to match them perfectly. So stop
spamming that corner for 10 seconds cause he's already behind you :p. In a
straight up shaft fight you want your crosshair to track the opponent with the
immediacy of a shadow (<3 Bruce Lee), and you can only achieve this through
total presence.

Just like we discussed earlier with enemy status, putting yourself in the right
situation with aim also has an enormous value. You're not going to miss that
jump pad shot when you're 200/200 and have every item in the map on lock. The
reason? Comfortability and simplicity. You're comfortable because you're in the
exact situation you need to be, add that to the fact that the shot is the simplest
shot in the game and probably doesn't even require you to move - and you have
yourself a winner :)

Motivation, Attitude (Pushing the limits)

It's important to keep a healthy morale when you go to play a game. Sometimes
you just aren't motivated. If you're not feeling up to a game, don't play. It takes
discipline just to take a break sometimes. A lot of players think, "Man, I keep
losing because I'm playing bad... I'm playing badly because I don't feel like
playing... but I need to get better so I have to keep playing." This is a vicious
cycle that traps almost every aspiring pro*** at some point. If you find yourself
in that situation you just need to remind yourself that it's the quality that counts.
Taking into account the stress of tournaments, it may all be a bit overwhelming at
times. If you're new to the scene, you might be freaking out months before the
tournament even starts. If you take my previous advice, you know its not smart
to practice when you're stressed because you'll be too emotional to concentrate
or play your best. So how will you get practice if you're purposely not playing
because the pressure is too high? The answer is simple. Do what you can with
what you have, and, you receive what you give.

"Do what you can with what you have." What I mean by this is, you do as much
as you can with what you're given. Whatever that means, whatever situation you
are in. If you're stressed out and you can't seem to calm down, you have may
have no choice but to play through it. You gotta accept that you're just going to
suck while you play. If you can't practice for a solid week before an event, what
can you do about it? Do everything you can but don't resist it psychologically. You
have to bring peace into the game in order to maintain functionality because....
"You receive what you give." Give it nothing, you can expect to receive nothing.
Give it your all, every, single, time-- you're going to get something back. If it's
not enough for you, too bad - give it some more. How is there a choice in the
matter? And don't just give it more- give it better, brighter. Give it lightness,
freedom, joy, enthusiasm. See what you get back. Life is the journey, a beautiful
means through uncertainty. So you start with what you have, and you do what
you can with it. Give it your all, Good luck.

Resolve. (Conscious adaptation)

Alright, so I'm practicing really hard and I'm paying acute attention to everything
thats happening - but I still having troubles with such-and-such problem(s). This
is where resolve comes in. Resolve is my favorite word, it just means so much
(seriously, it has 18 definitions on dictionary.com.) I said at the beginning of this
article that discipline may be the most important aspect of an individuals ability,
to me resolve plays a key just above that. Resolve gives you the ability to take a
step back, and tackle the problem again from a different angle. Or maybe just
tackle it harder this time. Or maybe lets try diving in on it from above. What if we
dug a hole and trapped the problem in a pit of spikes? No, I've got it... we'll use
magnets!... haha

A brilliant player (you know who you are) once told me repeatedly to think
outside the box. I kept thinking to myself, "What does that even mean?" I think
the answer to that question, or any question, is the fruit of resolve. With your
resolve you have ability to adapt, rework, recreate, restore, regenerate, renew.
Resolve is the forge by which the blade of your will is tempered. And like any
great sword, it must be shaped, heated, cooled, and folded thousands of times
before it is perfect - but who is ever perfect?
The end.

I want to remind you that while all these insights are important, and though its
important to gather new knowledge - the core of your concentration while playing
should be on enemy status, and timing. These two components are the basis for
all in-game decision making.

Hopefully this article has given you some knew knowledge or at least a fresh
perspective on things. If you still find yourself getting stuck, try writing stuff
down, you can build a journal or progress report of sorts this way.
It's been fun sharing with you all! Keep at it and together we will improve the
meta game! See you on the interwebs =]

Sound 101

So today I wanted to purchase new head phones. Just when I got back I was just wanting to confirm the specifications that I used to purchase. Which by the way, I purchased the JVC HA-S600-B from Fry's. 

I specifically liked the frequency range of the sound - 8Hz-25KHz. So it had a nice range of bass as well as treble.

Here is a cool website that explained everything that goes on behind sound engineering. - http://www.tech-forums.net/forums/f12/sound-101-a-169733/
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So... you're lookin fer some bumpin speakers eh? Well, heres some tips for you. Headphones can also follow these guidelines!

First of all, wattage isn't everything. Wattage is only the power your feeding to it. Also, especially when looking at 5.1 or 7.1 systems, when the box says "A WHOPPING 100w!", you have to remember... that 100watts is divided 6 ways (5.1) or even 8 ways (7.1). Usually, the sub will get most of the power and the satellites will get a miniscule amount. Higher wattage is good, but not always better. As this is just basic information, I'm not going to get into RMS and Peak power ratings, but researching these two forms of power is DEFINITELY a must when looking at speakers/amps. Also, resistance (ohms) is another thing you may want to dabble into.

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Since wattage isn't everything, what is? Sensitivity!!! Ok... so you spent your hard earned cash on some awesome speakers with 500 watts of power. Freakin sweet eh? You open the box, get everything all set up and you go to press PLAY anxiously waiting for your heart to be resuscitated by the massive 500watts flowing through them speakers. You press play and what you hear is good. Then you take the dive and turn the volume up. "WTF?! I've got these things all the way up and they aren't loud whatsoever!! WHAT BS!!!" Sensitivity my good friend. So what is sensitivity? Well, in most specifications you will see a section called Signal to noise ratio (SNR) or sensitivity. Then you will get a number followed by dB (decibels). Say this number is 50dB (which is horrendous), that means for every one watt of power going in, 50 decibels of sound will come out (if playing white noise at nominal level). Most consumer quality stuff ranges from 70-80's. You really want at least 89dB. Anything above 90 will give you plenty of volume and will use its wattage more efficiently.

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Anything else? DUH! We haven't even scratched the surface! Frequency range!! Frequency range is that weird section of numbers that no one ever understands. (100-20,000hz). What the heck does that mean? Well, hz (hertz) is a measurement of how many times a sound wave cycles in one second. So, the lower the number, the slower the wave. Thusly, the slower the wave, the lower it sounds. The human hearing range is technically 20hz-20,000hz (or 20khz). I consider the USABLE range to be 30hz-18khz Although I can hear 20-20k, people above 25 years old(ranges) can't hear much above 17k due to hearing damage (no matter what you do, it happens when you get older).

A GOOD frequency range is having the first number as low as possible and the second number as high as possible. So, if your speakers have a 75hz-16,000hz (which is not so great) range, if you play anything below or above those numbers, you wont hear it as your speakers can't play it. Chest thumping is normally found around 30-60hz. A good range I like to follow is to keep the first number below 50hz and the high number at least at 18khz (or 18,000hz).

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Digital versus analog! WHAT?! THERE ARE NO SUCH THINGS AS DIGITAL SPEAKERS! NEVER! Speakers are purely an analog mechanism. A speaker consists of a magnet, a voice coil, a spider and a cone (with a dust cap in the middle, which really serves no purpose). Essentially, the speaker vibrates (in AND out) to move molecules which form sound waves. When a description says DIGITAL SPEAKERS, that means it has a digital to analog converter (AD/DA) OR it has a digital decoder built in. Digital connections only transmit information. No audio whatsoever. Just a bunch of ones and zeros.

So now you should have a basic understanding about speakers and headphones. Now, go out and get yourself some GOOD speakers (excluding Bose).

Whats next? Wiring!

Let's say you've got some sweet speakers and a really sweet amp. Rock on eh? Car install, home theater, whatever... wiring it all up goes here! There are a few different ways to wire things up, but first we gotta understand the basics:

• Ohms (impedence or resistance)
• Wattage
• Load
• Phase

Let's start with resistance! This can be quite the challenge, but its quite simple. Every speaker has a level of resistance, called impedence. Impedence is measured in what's called Ohm's. Now, we could get crazy and go into Ohm's Law, but theres really no point without going into some advanced stuff. Just so you can see it, here is the Ohm's Law chart:



This is used for figuring Impedence (resistance), wattage, voltage, and current. Simple math as long as you know the information. Anyways, back to resistance. You know how on your amplifier it says it can handle X amount of ohms? Well, thats what is called Load. 8ohms and 4ohms are the most common, but there are components that run even lower than that. How do we figure out load? Well, that all depends on how things are wired up. There are three ways to wire: Series, Parallel, and Series Parallel (I know, scary... don't worry). When hooking up more than one speaker, you have to use one of these wiring methods. Though it may seem obvious, but "black goes to black and red goes to red". These are the positive and negative leads. This gets into phase, which we'll learn a bit later.

Series:



As you can see, there are two 8ohm speakers hooked up. When you wire them in series method, you add the resistance of all of the speakers, and you get your load. In this case, 8+8= 16ohm load. REMEMBER! The higher the resistance, the lower the output. Why? Most amplifiers can handle high loads. The less resistance there is, the more power the speakers will draw from the amp, the more output (and we all know what that means... LOUDER!). The smaller load rating on the amp, the better. If the amp can handle 2 ohms, you better be sure it can give you more than enough power for any application. In the case of the picture above, it won't be very hard at all for the amp to drive those two speakers, but keep in mind that it sure isn't going to get that loud. It may be better to wire it in a different method, such as parallel!


Parallel:



Here we have the same to speakers, but wired differently. When wiring in parallel, you multiply the resistance of all of the speakers, and divide it by the sum of all the resistance of the speakers. This will give you your load rating. Here we have two 8ohm speakers wired in parallel. So, we take 8 * 8 = 64 ---- 64 / 16 = 4 ---- This gives us a load of 4ohms. If we were to hook up this to the same amplifier as we did with series, we would get a much high output since it is drawing much more power from the amp.

Series Parallel

Embedded Systems Interview Review

Today, I have a few interviews lined up. I want to do well of course, so I thought I would lay out some interview review.

Let's begin!

A really awesome review is linked here- http://www.sanjayahuja.com/Interview%20questions.pdf
--------------
This information came from- http://careerride.com/embedded-systems-interview-questions.aspx

What is the need for an infinite loop in Embedded systems?

Infinite Loops are those program constructs where in there is no break statement so as to get out of the loop, it just keeps looping over the statements within the block defined.
Example:
While(1) {}

OR

for(;;);
{
//Code
}
Embedded systems need infinite loops for repeatedly processing/monitoring the state of the program. One example could be the case of a program state continuously being checked for any exceptional errors that might just occur during run time such as memory outage or divide by zero etc.,

For e.g. Customer care Telephone systems where in a per-recorded audio file is played in case the dialer is put on hold..

Also circuits being responsible for indicating that a particular component is active/alive during its operation by means of LED's.

How does combination of functions reduce memory requirements in embedded systems?

The amount of code that has to be dealt with is reduced thus easing the overhead and redundancy is eliminated in case if there is anything common among the functions.

Memory allocation is another aspect that is optimized and it also makes sense to group a set of functions related in some way as one single unit rather than having them to be dispersed in the whole program.

In case of interactive systems display of menu list and reading in the choices of user's could be encapsulated as a single unit.

A vast majority of High Performance Embedded systems today use RISC architecture why?

According to the instruction sets used, computers are normally classified into RISC and CISC. RISC stands for 'Reduced Instruction Set Computing' .The design philosophy of RISC architecture is such that only one instruction is performed on each machine cycle thus taking very less time and speeding up when compared to their CISC counterparts.

Here the use of registers is optimized as most of the memory access operations are limited to store and load operations.

Fewer and simple addressing modes, and simple instruction formats leads to greater efficiency, optimization of compilers, re-organisation of code for better throughput in terms of space and time complexities. All these features make it the choice of architecture in majority of the Embedded systems.

CISC again have their own advantages and they are preferred whenever the performance and compiler simplification are the issues to be taken care of.

CISC	RISC
Emphasis on hardware	Emphasis on software
Includes multi-clock complex instructions	Single-clock, reduced instruction only
Memory-to-memory: "LOAD" and "STORE" incorporated in instructions	Register to register: "LOAD" and "STORE" are independent instructions
Small code sizes, high cycles per second	Low cycles per second, large code sizes
Transistors used for storing complex instructions	Spends more transistors on memory registers

However, the RISC strategy also brings some very important advantages. Because each instruction requires only one clock cycle to execute, the entire program will execute in approximately the same amount of time as the multi-cycle "MULT" command. These RISC "reduced instructions" require less transistors of hardware space than the complex instructions, leaving more room



The Performance Equation
The following equation is commonly used for expressing a computer's performance ability:

The CISC approach attempts to minimize the number of instructions per program, sacrificing the number of cycles per instruction. RISC does the opposite, reducing the cycles per instruction at the cost of the number of instructions per program. 

 

 (above table- http://www-cs-faculty.stanford.edu/~eroberts/courses/soco/projects/risc/risccisc/)

Why do we need virtual device drivers when we have physical device drivers?

Device drivers are basically a set of modules/routines so as to handle a device for which a direct way of communication is not possible through the user's application program and these can be thought of as an interface thus keeping the system small providing for minimalistic of additions of code, if any.
Physical device drivers can’t perform all the logical operations needed in a system in cases like IPC, Signals and so on...
The main reason for having virtual device drivers is to mimic the behaviour of certain hardware devices without it actually being present and these could be attributed to the high cost of the devices or the unavailability of such devices.
These basically create an illusion for the users as if they are using the actual hardware and enable them to carryout their simulation results.
Examples could be the use of virtual drivers in case of Network simulators,also the support of virtual device drivers in case a user runs an additional OS in a virtual box kind of a software.

What is the need for DMAC in ES?

Direct memory access is mainly used to overcome the disadvantages of interrupt and progam controlled I/O.
DMA modules usually take the control over from the processor and perform the memory operations and this is mainly because to counteract the mismatch in the processing speeds of I/O units and the procesor.This is comparatively faster.

It is an important part of any embedded systems,and the reason for their use is that they can be used for bursty data transfers instead of single byte approaches.
It has to wait for the systems resources such as the system bus in case it is already in control of it.

What is Endianness of a system and how do different systems communicate with each other?

Endianness basically refers to the ordering of the bytes within words or larger bytes of data treated as a single entity.
When we consider a several bytes of data say for instance 4 bytes of data,XYZQ the lower byte if stored in a Higher address and others in successively decreasing addresses ,then it refers to the Big Endian and the vice versa of this refers to Little Endian architecture.
Intel 80x86 usually follows Little Endian and others like IBM systems follow Big Endian formats.
If the data is being transmitted care has to be taken so as to know as to which byte,whether the higher or the lower byte is being transmitted.
Hence a common format prior to communication has to be agreed upon to avoid wrong interpretation/calculations.
Usually layer modules are written so as to automate these conversion in Operating systems.


"Little Endian" means that the low-order byte of the number is stored in memory at the lowest address, and the high-order byte at the highest address. (The little end comes first.) For example, a 4 byte LongInt

    Byte3 Byte2 Byte1 Byte0

will be arranged in memory as follows:

    Base Address+0   Byte0
    Base Address+1   Byte1
    Base Address+2   Byte2
    Base Address+3   Byte3

Intel processors (those used in PC's) use "Little Endian" byte order. "Big Endian" means that the high-order byte of the number is stored in memory at the lowest address, and the low-order byte at the highest address. (The big end comes first.) Our LongInt, would then be stored as:

    Base Address+0   Byte3
    Base Address+1   Byte2
    Base Address+2   Byte1
    Base Address+3   Byte0

Motorola processors (those used in Mac's) use "Big Endian" byte order.
^Found from http://people.cs.umass.edu/~verts/cs32/endian.html

How are macros different from inline functions?

Macros are normally used whenever a set of instructions/tasks have to be repeatedly performed. They are small programs to carryout some predefined actions.
We normally use the #define directive in case we need to define the values of some constants so in case a change is needed only the value can be changed and is reflected throughout.
#define mul(a,b) (a*b)
The major disadvantage of macros is that they are not really functions and the usual error checking and stepping through of the code does not occur.
Inline functions are expanded whenever it is invoked rather than the control going to the place where the function is defined and avoids all the activities such as saving the return address when a jump is performed. Saves time in case of short codes.
inline float add(float a,float b)
{
return a+b;
}
Inline is just a request to the compiler and it is upto to the compiler whether to substitute the code at the place of invocation or perform a jump based on its performance algorithms.

What could be the reasons for a System to have gone blank and how would you Debug it?

Possible reasons could be,
- PC being overheated.
- Dust having being accumulated all around.
- CPU fans not working properly .
- Faulty power connections.
- Faulty circuit board from where the power is being drawn.
- Support Drivers not having being installed.

Debugging steps which can be taken are:

- Cleaning the system thoroughly and maintaining it in a dust-free environment.
Environment that is cool enough and facilitates for easy passage of air should be ideal enough.

- By locating the appropriate support drivers for the system in consideration and having them installed.

Explain interrupt latency and how can we decrease it?

Interrupt latency basically refers to the time span an interrupt is generated and it being serviced by an appropriate routine defined.,usually the interrupt handler.
External signals,some condition in the program or by the occurrence of some event,these could be the reasons for generation of an interrupt.
Interrupts can also be masked so as to ignore them even if an event occurs for which a routine has to be executed.
Following steps could be followed to reduce the latency
- isrs being simple and short.
- Interrupts being serviced immediately
- Avoiding those instructions that increase the latency period.
- Also by prioritizing interrupts over threads.
- Avoiding use of inappropriate APIs.

How to create a child process in linux?

Prototype of the function used to create a child process is pid_t fork(void);
Fork is the system call that is used to create a child process. It takes no arguments and returns a value of type pid_t.
If the function succeeds it returns the pid of the child process created to its parent and child receives a zero value indicating its successful creation.
On failure, a -1 will be returned in the parent's context, no child process will be created, and errno will be set
The child process normally performs all its operations in its parents context but each process independently of one another and also inherits some of the important attributes from it such as UID, current directory, root directory and so on.

Significance of watchdog timer in Embedded Systems

Watchdog timer is basically a timing device that is set for predefined time interval and some event should occur during that time interval else the device generates a time out signal.
One application where it is most widely used is when the mobile phone hangs and no activity takes place,in those cases watchdog timer performs a restart of the system and comes to the rescue of the users.
It is used to reset to the original state whenever some inappropriate events take place such as too many commands being given at the same time or other activities that result in malfunctioning of the GUI.It is usually operated by counter devices.

If you buy some RTOS, what are the features you look for in ?

-Deterministic operating system having guaranteed worst-case interrupt latency and context-switch times.
-Documentation providing for the minimum, average, and maximum number of clock cycles required by each system call
-Interrupt response times should be very minute.
-Context switch time should be very low.
-Compatibility with several plugin devices.
- Overall it should be very reliable.

Why is java mostly used in embedded systems?

Java was mainly designed and conceputalised for code that can work on different platforms without any hassles and also for being secure enough so as to not harm or corrupt other modules of code.
Features like exception handling,simple syntax and Automatic Garbage collection all work in its favour as the language for use in ES's.
Also that it is widely used in the form of Java applets makes it very popular confining it to the limits of JVM.It is Dynamic in nature.
Its use is also being exploited in enterprise systems in the form of J2EE ,J2SE
J2ME in case of mobile applications.

Differentiate between mutexes vs semaphores

-Semaphores is a synchronisation tool to overcome the critical section problem.
- A semaphore S is basically an integer variable that apart from initialisation is accesses only through atomic operations such as wait() and signal().
- Semaphore object basically acts as a counter to monitor the number of threads accessing a resource.
- Mutex is also a tool that is used to provide deadlock free mutual exclusion.It protects access to every critical data item.if the data is locked and is in use,it either waits for the thread to finish or awakened to release the lock from its inactive state.

What are the commonly found errors in Embedded Systems?

- Damage of memory devices due to transient current and static discharges.
- Malfunctioning of address lines due to a short in the circuit
- Malfunctioning of Data lines.
- Some memory locations being inaccessible in storage due to garbage or errors.
- Improper insertion of Memory devices into the memory slots
- Faulty control signals.

What is the need for having multibyte data input and output buffers in case of device ports?

It’s normally the case that some devices transfer the output either in a bursty or a sequential manner and also during input entry. If we take the example of keyboards, all the data entered is stored in a buffer and given at a time or one character at a time.
In case of networking there may be several requests to access the same resource and all these are queued in a buffer and serviced in the order they are received
Hence to avoid the input/output units from getting overloaded with requests, we use multibyte buffers.

--------------
The following are basic interview questions for embedded systems - found http://careerride.com/embedded-systems-interview-for-freshers.aspx

What is lst file?

• This file is also called as list file.
• It lists the opcodes ,addresses and errors detected by the assembler.
• List file is produced only when indicated by the user.
• It can be accessed by an editor and displayedon monitor screen or printed.
• Progammer uses this file to find the syntax errors and later fix them.

How is a program executed’ bit by bit’ or’ byte by byte’?

EXAMPLE

ADDRESS	OPCODE	PROGRAM
1   0000		ORG 0H
2   0000	7D25	MOV R5,#25H
3   0002	7F34	MOV R7,#34H
4   0004	2D	ADD A, R5
5   0005		END

• A program is always executed byte by byte.
• Firstly,1st opcode 7D is fetched from location 0000 and then the value 25 is fetched from 0001 .
• 25 is then placed in the register R5 and program counter is incremented to point 0002.
• On execution of opcode 7F, value 34 is copied to register R7.
• Then addition of contents of R5 and accumulater takes place.
• Here all the opcodes are 8 bit forming a byte.

Explain DB.

• DB is called as define byte used as a directive in the assembler.
• It is used to define the 8 bit data in binary ,hexadecimal or decimal formats.
• It is the only directive that can be used to define ASCII strings larger than two characters.
• DB is also used to allocate memory in byte sized chunks.
• The assembler always converts the numbers lnto hexadecimal.

What is EQU?

• EQU is the equate assmbler directive used to define a constant without occupying a memory location.
• It associates a constant value with data label .
• Whenever the label appears in the program ,constant value is subsituted for label.
• Advantage: The constant value occuring at various positions in a program can be changed at once using this directive.
• Syntax: label EQU constant value

How are labels named in assembly language?

• Label name should be unique and must contain alphabetic letters in both uppercase and lowercase.
• 1st letter should always be an alphabetic letter.
• It can also use digits and special characters ?,.,@,_,$.
• Label should not be one of the reserved words in assembly language.
• These labels make the progam much easier to read and maintain.

Are all the bits of flag register used in 8051?

• The flag register also called as the program status word uses only 6 bits.
• The two unused bits are user defineable flags.
• Carry ,auxillary carry ,parity and overflow flags are the conditional flags used in it.
• PSW.1 is a user definable bit and PSW.5 can be used as general purpose bit.
• Rest all flags indicate some or the other condition of an arithematic operation.

Which bit of the flag register is set when output overflows to the sign bit?

• The 2nd bit of the flag register is set when output flows to the sign bit.
• This flag is also called as the overflow flag.
• Here the output of the signed number operation is too large to be accomodated in 7 bits.
• For signed numbers the MSB is used to indicate the whether the number is positive or negative.
• It is only used to detect errors in signed number operations. 

Which register bank is used if we use the following instructions
SETB  PSW.3      A
SETB  PSW.4       B

• Statement A sets 3rd bit of flag register.
• Statement B sets 4th bit of flag register.
• Therefore register bank 3 is initiated .
• It uses memory location 18H to 1FH.
• The register bank is also called as R3.

Issues related to stack and bank 1.

• Bank 1 uses the same RAM space as the stack.
• Stack pointer is incremented or decremented according to the push or pop instruction.
• If the stack pointer is decremented it uses locations 7,6,5… which belongs to register bank 0.
• If a given program uses R1 then stack is provided new memory location.
• The push instruction may also take stack to location 0 i.e.it will run out of space.

Explain JNC.

• It is a command used to jump if no carry occurs after an arithematic operation.
• It is called as jump if no carry( conditional jump instruction).
• Here the carry flag bit in PSW register is used to make decision.
• The processor looks at the carry flag to see if it is raised or not.
• If carry flag is 0 ,CPU fetches instructions from the address of the label.

Write a program to toggle all bits of P1 every 200ms.

                    MOV              A,#55H
AGAIN:       MOV              P1,A
                    ACALL          DELAY
                    CPL               A
                    SJMP            AGAIN

DELAY:
                    MOV              R5,#9
HERE1:     MOV              R4,#242
HERE2:     MOV              R3,#255
HERE3:     DJNZ            R3,HERE3
                    DJNZ            R4,HERE2
                    DJNZ            R5,HERE1
                    RET
• Here the delay produced is 9*255*4MC*90=199,940 micro seconds.
• CPL is used to toggle the bits of P1.
• Short jump is jusd to produce a continuous loop.

Can port 0 be used as input output port?

• Yes, port 0 can be used as input output port.
• Port 0 is an open drain unlike ports 2,3,4.
• To use it as input or output the 10k ohm pull-up resisters are connected to it externally.
• To make port 0 as input port it must be programmed by writing 1 to all bits.
• Example:

MOV  A,#0FFH
MOV  P0,A

Which 2 ports combine to form the 16 bit address for external memory access?

• Port0 and port2 together form the 16 bit address for external memory.
• Port0 uses pins 32 to 39 of 8051 to give the lower address bits(AD0-AD7)
• Port2 uses pins 21 to 28 of 8051 to give the higher address bits(A8-A15)
• This 16 bit address is used to access external memory if attached.
• When connected to external memory they cannot be used as input output ports.

Can single bit of a port be accessed in 8051?

• Yes,8051 has the capability of accessing only single bit of a port.
• Here only single bit is accessed and rest are unaltered.
• SYNTAX: “SETB X. Y”.
• Here X is the port number and y is the desired bit.
• Example: SETB P1.2

Here the second bit of port 1 is set to 1.

Other than SETB ,CLR are there any single bit instructions ?

• There are total 6 single-bit instructions.
• CPL bit : complement the bit (bit= NOT bit).
• JB bit,target: Jump to target if bit equal to 1.
• JNB bit,target: Jump to target if bit is equal to 0.
• JCB bit,target: Jump to target if bit is equal to 1 and then clear bit.

Review Buck, Boost, LDO, PWM, and FIR vs IIR

Charis Poag, 1/5/13

The following information was obtained for a company I am applying for (omitted name). One of the Design directors asked me some questions during the interview. So I went ahead and did some research to refresh my mind on their technologies over the weekend.  

Power i nformation came from: http://users.ece.utexas.edu/~kwasinski/teaching.html and some from Wikipedia and youtube videos.

Main knowledge of DSP information came from: http://users.ece.utexas.edu/~bevans/courses/realtime/lectures/index.html

a) Buck converters-

A buck converter is a method to "step-down DC to DC converter".   Our goal is to have a high efficiency design, ie our lossless objective: Power in = power out, thus Vin*Iin =Vout*Iout -> Vout/Vin = Iin/Iout. The typical buck converter design is shown in the figure below.

Note: the switch is typically a MOSFET,IGBT, or BJT.

Idea: voltage regulation by the inductor--

Also energy stored in an inductor is described as-

The theory of operation is fairly simple, with an inductor and two switches (usually created with a transistor and a diode) which controls the inductor converter. The best way to understand this is to think in terms of the inductor's reluctance to allow a change in current. So when the switch is open (seen in picture below as the "off" position), the current in the circuit is 0 in the beginning. But when the switch is closed, the current begins to increase, but the inductor does not want it to change from 0, so it attempts to fight the increase by dropping the voltage. The voltage drop counters the voltage of the source and reduces the net voltage across the load. Over time, the inductor allows current to increase slowly by  decreasing the voltage it drops, thus increasing the net voltage seen by the load. This process causes the inductor to store the energy in the form of a magnetic field.

If the switch is opened before the inductor fully charges (in other words, before it has allowed all current to pass through by reducing its own voltage drop to 0), then there will always be a voltage drop across it. Thus the net voltage seen by the load is always less than the input voltage source. Overtime, the inductor allows the current to decrease gradually, which it does by decreasing the voltage across itself. During this time, the inductor is discharging its stored energy into the rest of the circuit.

If the switch is closed again before the inductor fully discharges, the load will always see a non-zero voltage. The capacitor placed in parallel with the lad helps smooth out this voltage waveform as the inductor charges and discharges each cycle. As seen in the figure below the circuit diagrams.

By keeping the inductor in a state of not fully charging and discharging we are able to create a circuit which lowers the output voltage. This also allows us to control the power efficiency of the circuit. A more in depth discussion of this circuit can be found on Wikipedia or other educational resources which describe the continuous and discontinuous modes of the inductors cycles and control of the current seen across the load. For example in continuous mode if you can find out what duty cycle you need to  step down 12v to 3v. In that particular case you need a 25% duty cycle in our theoretical ideal circuit.

This is due to D (uty cycle) =Vout/Vin =0.25 duty cycle.

http://en.wikipedia.org/wiki/Buck_converter

b) Boost converters-

 Note: the switch is typically a MOSFET,IGBT, or BJT.

Idea: voltage regulation by the inductor--

Also energy stored in an inductor is described as-

The circuit above is used to take a DC voltage and raise it to a higher DC voltage. The DC-to-DC power converter uses switched-mode power supply (SMPS) containing at least two semiconductor switches (a diode and a transistor) with at least one energy storage element, a capacitor, inductor or the two in combination. Filters made of capacitors(sometimes in combination with inductors) are normally added to the output of the converter to reduce output voltage ripple.

 This is also called a "step up converter" because it steps up the voltage source. Since power must be conserved (P=VI), the output current is lower than the source current. And as mentioned in the Buck converter, we  use the inductors capability to control the voltage, due to the rate of change of current across itself. Boost converters are often used for DC sources such as batteries, solar panels, rectifiers and DC generators.

The circuit analysis is quite similar to the buck converter. As mentioned in that section, we use the inductor to resist changes in current, thus controlling the voltage. In a boost converter, the output voltage is always higher than the input voltage.

The basic principle of the boost converter consists of two distinct states as see above:

1) The on state: the switch is closed, resulting in an increase of inductor current

2) The off state: the switch is open and the only path offered to the inductor current is through the flyback diode, the capacitor C and the load R. This results in transferring energy accumulated during the on state into the capacitor connected in parallel with the load.
 

To find out what duty cycle you need to say convert 12v to 24v then use the duty cycle conversion equation. D = 1-(12/24) = 1-0.5 = 0.5.

c) PWM-

Used for controlling power to inertial electrical devices, made practical my modern power switches. Longer the switch is on compared to off periods, the higher the power supplied to load is. PWM is use for several electronic application, including: telecommunications signal modulation,  power delivery to a load, voltage regulation, and audio effects/amplification.  An example of how PWM is used to convert digital signal to an analog signal is shown below.

Above is an example to control speed of a motor. Lets say the duty cycle = time on/time off = 0.5 voltage swings from 0 to 12 volts. Then average voltage = 0.5 * 12v = 6volt average being supplied to the motor.

**Also used for Digital to Analog converter.

From my experience , an easy way of creating a duty cycle could be done by using a microcontroller which you can turn off and on an output voltage that is  controlled with a timing interrupt. A wonderful reference for a PWM driver can be found on my professor Valvano's website (http://users.ece.utexas.edu/~valvano/EE345L/Lectures/LLec27_PWMmotor.pdf)

Example code of a timer to create PWM on an ARM processor can be found below.

Here are some examples of duty cycles:

// Timer0APWM.c

// Runs on LM3S811

// Use Timer0A in PWM mode to generate a square wave of a given

// period with 50% duty cycle.

// Daniel Valvano

// June 27, 2011

/* This example accompanies the book

   "Embedded Systems: Real Time Interfacing to the Arm Cortex M3",

   ISBN: 978-1463590154, Jonathan Valvano, copyright (c) 2011

 Copyright 2011 by Jonathan W. Valvano, valvano@mail.utexas.edu

    You may use, edit, run or distribute this file

    as long as the above copyright notice remains

 THIS SOFTWARE IS PROVIDED "AS IS".  NO WARRANTIES, WHETHER EXPRESS, IMPLIED

 OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF

 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE.

 VALVANO SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL,

 OR CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.

 For more information about my classes, my research, and my books, see

 http://users.ece.utexas.edu/~valvano/

 */

#define TIMER0_CFG_R            (*((volatile unsigned long *)0x40030000))

#define TIMER0_TAMR_R           (*((volatile unsigned long *)0x40030004))

#define TIMER0_CTL_R            (*((volatile unsigned long *)0x4003000C))

#define TIMER0_TAILR_R          (*((volatile unsigned long *)0x40030028))

#define TIMER0_TAMATCHR_R       (*((volatile unsigned long *)0x40030030))

#define TIMER0_TAMATCHR_R       (*((volatile unsigned long *)0x40030030))

#define TIMER_CFG_16_BIT        0x00000004  // 16-bit timer configuration,

                                            // function is controlled by bits

                                            // 1:0 of GPTMTAMR and GPTMTBMR

#define TIMER_TAMR_TAAMS        0x00000008  // GPTM TimerA Alternate Mode

                                            // Select

#define TIMER_TAMR_TAMR_PERIOD  0x00000002  // Periodic Timer mode

#define TIMER_CTL_TAEN          0x00000001  // GPTM TimerA Enable

#define TIMER_TAILR_TAILRL_M    0x0000FFFF  // GPTM TimerA Interval Load

                                            // Register Low

#define TIMER_TBILR_TBILRL_M    0x0000FFFF  // GPTM TimerB Interval Load

                                            // Register

#define GPIO_PORTD_AFSEL_R      (*((volatile unsigned long *)0x40007420))

#define GPIO_PORTD_DEN_R        (*((volatile unsigned long *)0x4000751C))

#define SYSCTL_RCGC1_R          (*((volatile unsigned long *)0x400FE104))

#define SYSCTL_RCGC2_R          (*((volatile unsigned long *)0x400FE108))

#define SYSCTL_RCGC1_TIMER0     0x00010000  // timer 0 Clock Gating Control

#define SYSCTL_RCGC2_GPIOD      0x00000008  // port D Clock Gating Control

void WaitForInterrupt(void);  // low power mode

// period is number of clock cycles in PWM period ((1/clock) units)

void PWOut_Init1(unsigned short period){

  volatile unsigned long delay;

  SYSCTL_RCGC1_R |= SYSCTL_RCGC1_TIMER0;// activate timer0

  SYSCTL_RCGC2_R |= SYSCTL_RCGC2_GPIOD; // activate port D

  delay = SYSCTL_RCGC2_R;          // allow time to finish activating

  GPIO_PORTD_DEN_R |= 0x10;        // enable digital I/O on PD4

  GPIO_PORTD_AFSEL_R |= 0x10;      // enable alt funct on PD4

  TIMER0_CTL_R &= ~TIMER_CTL_TAEN; // disable timer0A during setup

  TIMER0_CFG_R = TIMER_CFG_16_BIT; // configure for 16-bit timer mode

                                   // configure for alternate (PWM) mode

  TIMER0_TAMR_R = (TIMER_TAMR_TAAMS|TIMER_TAMR_TAMR_PERIOD);

  TIMER0_TAILR_R = period-1;       // timer start value

//  TIMER0_TAMATCHR_R = period/4;    // duty cycle = 75%

  TIMER0_TAMATCHR_R = period/2;    // duty cycle = 50%

//  TIMER0_TAMATCHR_R = 3*period/4;    // duty cycle = 25%

  TIMER0_CTL_R |= TIMER_CTL_TAEN;  // enable timer0A 16-b, PWM, 50% duty

}

//debug code

int main(void){

//  PWOut_Init1(300);                // initialize timer0A in PWM mode (20,000 Hz)

//  PWOut_Init1(1200);               // initialize timer0A in PWM mode (5,000 Hz)

  PWOut_Init1(6000);               // initialize timer0A in PWM mode (1,000 Hz)

  while(1){

    WaitForInterrupt();

  }

}

d) LDO-

http://www.analog.com/library/analogDialogue/archives/41-05/ldo.html

For the circuit above (LDO) the output voltage is defined as

A "low-dropout" regulator is used for DC voltage regulators which operate with a very small input-output differential voltage. The advantage for using a low dropout voltage is because they a lower minimum operation voltage, but higher efficiency operation and heat dissipation.

Primarily, the main components for an LDO circuit consists of a power FET and a differential amplifier (error amplifier). One input of the differential amplifier monitors the fraction of the output determined by the resistor ratio of R1 and R2. The second input to the differential amplifier is from a stable voltage reference (bandgap reference). If the output voltage rises too high relative to the reference voltage, the drive to the power FET changes to maintain a constant output voltage.

These LDO regulators work in the same way as all linear voltage regulators, however the main difference is their schematic topology. Instead of an emitter follower topology (shown below, low-dropout regulators use open collector or open drain topology. This allows transistor saturation, which allows the voltage drop from the unregulated voltage to the regulated voltage to be as low as the saturation voltage across the transistor.

Figure: PNP version of the emitter follower circuit

Just for my reference, I added a quick discussion of transistors. The transistor allows it to function as an amplifier or switch. This is accomplished by using a small amount of electricity to control a gate on which larger supply of electricity. The transistor's supply of voltage is comparable to turning a valve to control a supply of water. 

Transistors have 3 parts: base, collector, and emitter. The base is the gate controller for the device for larger electrical supply the emitter is the outlet for the supply. The collector is the larger electrical supply, and the emitter is the outlet for that supply. By sending varying levels of current from the base, the amount of current flowing through the gate from the collector can be regulated. In this way, a very small amount of current may be used to control a large amount of current, for example within an amplifier. The same process is used to create binary code for digital processors, but in this case a voltage threshold of 5 volts is needed to open the collector gate. This process allows the transistor to be used as a switch with binary function of - 5 volts = on and less than 5 volts = off.

e) Advantages of FIR vs IIR filters

A wealth of information on FIR filters can be found here: http://www.eas.uccs.edu/wickert/ece2610/lecture_notes/ece2610_chap5.pdf

A wealth of information on IIR filters can be found here:

http://www.eas.uccs.edu/wickert/ece2610/lecture_notes/ece2610_chap8.pdf

Quick notes about the above information:

• x[n] is the input signal,
• y[n] is the output signal,
• are the filter coefficients, also known as tap weights, that make up the impulse response,
• is the filter order; an th-order filter has (N+1) terms on the right-hand side. The x[n-i] in these terms are commonly referred to as taps, based on the structure of a tapped delay line that in many implementations or block diagrams provides the delayed inputs to the multiplication operations. One may speak of a 5th order/6-tap filter, for instance

FIR- current input depends on pas and previous input samples as well as previous output samples.

	IIR (feedback)- y[n] = b0x[n]+b1x[n-1]+...+bmx[n-m] - a1y[n-1]-a2y[n-2]-any[n-N]	FIR- y[n] = b0x[n]+b1x[n-1]+...+bmx[n-N] = sum from i= 0 to N (bi * x[n-i])
stability	Can be unstable, can have limit cycles	Liner phase always possible, no limit cycles
Order	less	more
History	Derived from analog filters	No analog history
other		Polyphase implementation possible can always be made causal.
	Use less memory and calculations than similar FIR filters	More memory
	Recursive implementations (short order)	Too long and may cause various application problems (long order)

IIR filters are difficult to control and  have no particular phase, where as FIR filters make linear phase always possible. IRR can be unstable, whereas FIR is always stable. IIR, when compared to FIR, can have limited cycles, but FIR has no limited cycles. IIR is derived from analog, where as FIR has no analog history. IIR can make polyphase implementation possible, whereas FIR can be made casual (linear time-invariant system; depends only on past and present inputs, not future).