very new to embedded programming - can you look at my code for an AVR?

From: Michael Noone (mnoone.uiuc.edu_at_127.0.0.1)
Date: 11/29/04 

Date: Mon, 29 Nov 2004 07:14:05 GMT

Hi - I'm attempting to program an AVR so that through a computer
(through the serial port) one can easily control how fast it turns on
and turns off a single pin. This actually has a use (it will be used by
a grad student doing some research in nano EDM [electro discharge
machining]). I haven't been able to test it, so I don't have the
slightest clue if it works or not.

Essentially the entire design of it is that when you first turn on the
AVR, it initializes a couple basic things (enables timers, sets portc as
an output, initializes the stack, etc.) and then it waits for a command
from the serial port, analyzes it, and uses it to set the parameters of
the timer and to enable/disable all interrupts (thus enabling/disabling
the timer ISRs). The computer attached can also request certain
parameters if needs be.

It's written in lovely AVR assembler by yours truly. The only thing I
was able to test was the timer part of the code, as I could simulate
that with AVR Studio. (though strangely enough I think I found a couple
bugs with AVR Studio 4, as sometimes it would behave differently than
other times - even though I hadn't changed anything...)

The code between the computer and the AVR is fairly simple. Each message
is one byte long. If it's a command, the first set of 4 bits is the
command, the second set of 4 bits is the parameter (or 0x0 if it doesn't
need a parameter). Before a second byte can be sent (say when sending
the high and then low byte of one of the timer compares) the receiver
(AVR/computer) must give the transmitter (computer/AVR) permission. This
was done as the UART on the AT90S8515 can only hold one byte at a time.
I may move this code to a different avr eventually - but the AT90S8515
is the only AVR I've ever worked with, so I decided to go with it, even
though it's discontinued.

Anyways - the serial communication part of the code is 100% untested so
I'm not even sure if any of it works. All I know is that it compiles ok
:)

Most of the code is commented. The stuff that isn't is mostly redundant
stuff that I thought was fairly self explanatory.

Sorry for writing so much - I gotta work on that! Here's the assembler
file, let me know if you have trouble downloading it:

https://netfiles.uiuc.edu/mnoone/www/AT90S8515-serial-controlled-
oscillations.asm

Thanks!

-Michael Noone

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