Must have m4 installed, must have avr-as, avr-ld, avr-objcopy and avrdude.
ATTiny13 programed with ladyada's USBTinyISP (http://www.ladyada.net/make/usbtinyisp/)


To compile kears.asm:

./cmp.sh kears.asm


To program:

./program_avr.sh kears.ihex




If you have any comments or questions, send email to 'abetusk' at 'gmail' dot 'com'.

kears.asm should be functioning now, though I still need to play around
with the different PWM lengths for each state.  I would also like
to play around with adding more states (the "distracted" states)
so that's to be added.


The 'cmp.sh' script is doing the following:
m4 demo.S > demo.asm
avr-as -mmcu=attiny13 -o demo.o demo.asm
avr-ld -o demo.elf demo.o
avr-objcopy --output-target=ihex demo.elf demo.ihex
avrdude -c usbtiny -p t13 -U flash:w:demo.ihex



NOTES:

assumes attiny13 set to internal oscillator at 9.6 MHz

fuse high bits (e.g. fuseh.hex):
:01000000FF00
:00000001FF

fuse low bits (e.g. fusel.hex):
:010000007A85
:00000001FF

to program fuses:
sudo avrdude -c usbtiny -p t13 -U lfuse:w:0x7a:m
sudo avrdude -c usbtiny -p t13 -U hfuse:w:0xff:m
I think...


a note on timing:
we're assuming the attiny13 has been set to an internal
oscillator of 9.6 MHz
we've set up the timer0 overflow to increment once per
clock cycle, which means it should overflow once 
every 256 instructions.
so, 9,600,000 instructions / second
256 instructions / fire
-> 37,500 timer0 fires / second

dammit, can never remember:
Mega  10^6
milli 10^{-3}
micro 10^{-6}

the hxt900 (http://www.servodatabase.com/servo/hextronik/hxt900),
or compatible, servo wants a 450-2450 \mu s (microsecond) 
pulse width with a 20 ms (millisecond) pulse cycle

so, if we wanted to set up a counter in the timer0 overflow
to be on for x microseconds and cycle every y milliseconds

x 10^{-6} = ( X fires ) / ( 37,500 fires / second )
-> X = x * 37,500 / 10^6
-> Y = y * 37,500 / 10^3

for y = 20 milliseconds   -> Y     = 750      fires
for x = 450 microseconds  -> X_min = 16.875   fires
for x = 2450 microseconds -> X_max = 91.875   fires

and of course we have 8bit registers, so if we wanted
to count to 750, we need two registers with the
high bits being 2 and the low bits being 238
( ( 2*2^8 + 238 ) = 750 ).
This is where the values for HPW and LPW come from.
LLEFTC through RRIGHTC simarly come from choosing
values in the range of X_min and X_max.

I've chosen about DEBOUNCEH and DEBOUNCEL to be 
1/10th of a second (100 ms, what we generally 
believe to be 'instantaneous' as humans)
(14*256 + 166) = 3750 fires -> 1/10 second

I've chosen the button timer (how long you need
to press the button before it changes state)
to be .35 of a second.  I might want to decrease
this time a bit because it's noticeably slow.


NOTE (2):

The current working source is the 'kears.asm'.  
I originally programmed this in C but ran into 
size constraints with the ATtiny13 and had to 
switch over to assembly.  I have provided a 
previous version of the source, 'kears.c', in 
case anyone wants to play around with it or 
look at it.  The 'kears.c' should compile and 
work fine, just like the 'kears.asm', version, 
but without the extra 'wink' function (i.e. 
only two preset motions, the 'surprised' and 
'sad/angry' motions are available).

To compile kears.c:

fionna@Ooo:~$ ./cmp.sh

To program:

fionna@Ooo:~$ ./program_avr.sh kears.hex