Atmel program problem.

I've been trying to make a program for a atmel 90s1200 chip. The
program is located at http://zet.no/~vidarlo/program.asm .
It runs fine in Atmel AVR studio 3.56, and behaves like it is supposed
to. However, when deployed on a chip, it does not work at all, it seems
to run the fan subroutine all the time, no matter what switches is
pressed. I've tried it on a stk-500 developer card, and built the
circuit on a digital trainer, with debounced switches with pull-down
resistors. However, it still seems to run the fan loop all the time,
but it does not get stuck there. I've been running it at low frequency
to determine that it is not stuck, the leds come on and off!

 

[vidarlo@gmail.com]

Ok, thanks It worked with the correction you gave me. I just supposed
portB...oh, very well, portD...*ahem - learning to read documentation*

 

[Rich Webb]

On 17 Jan 2005 02:43:43 -0800, vidarlo@gmail.com wrote:

I've been trying to make a program for a atmel 90s1200 chip. The
program is located at http://zet.no/~vidarlo/program.asm .
It runs fine in Atmel AVR studio 3.56, and behaves like it is supposed
to. However, when deployed on a chip, it does not work at all, it seems
to run the fan subroutine all the time, no matter what switches is
pressed. I've tried it on a stk-500 developer card, and built the
circuit on a digital trainer, with debounced switches with pull-down
resistors. However, it still seems to run the fan loop all the time,
but it does not get stuck there. I've been running it at low frequency
to determine that it is not stuck, the leds come on and off!

....
ldi r16, 0xff ; puts 0xFF in register 16
out DDRB, r16 ; Sets bit in ddr for port B
....

Grrrr. I *hate* assembly that's commented like that; states the obvious
but doesn't explain what it's doing. Something like "Set all bits in
Port B as outputs" etc. would be nice...

....
main: ; start of main loop
in r17, portD ; Read data from port D, store in r17
andi r17, 7 ; Mask r17 with 7, to destroy all but last.
....

This is the problem. The register "PortD" is the port latch and, when
the port is set as an input, controls whether or not the internal
pull-ups are enabled. The value after reset is 0x00 so that's what
you'll always read and the app will always branch to the fan routine.
To read the value at the pins, you should read the register "PinD"
instead.

....
main: ; start of main loop
in r17, pinD ; Read data from port D, store in r17
andi r17, 7 ; Mask r17 with 7, to destroy all but last.
....

Not that *I've* ever made that mistake. <erm... cough cough>

--
Rich Webb Norfolk, VA