Lazy evening. I decided to take a couple of shots of couple generated signals. Without going too deep into timings, I wrote a couple of algorithms to ensure the signals are generated correctly at all voltage range 0-5V. First is the Sawtooth signal using ASM in AVRStudio:
.INCLUDE "m8def.inc"
.DEF tmp = R16 ; Multipurpose register
ldi tmp,0xFF; Set all pins of Port D as output
out DDRD,tmp
sawtooth:
out PORTD,tmp
inc tmp
rjmp sawtooth
(My oscilloscope is old, so sorry for the bad quality) Second signal Triangle. This one I programmed using the WinAVR toolset.
int main (void)
{
uint8_t x=0, y=0;
atmega8init();
for (;;) /* Note [6] */
{
if (y==0)
{
x++;
if (x==255) y=1;
}
else
{
x--;
if (x==0) y=0;
}
PORTD=x;
}
return (0);
}
It is evident that signals are generated correctly at all voltage interval 0-5V.
Later I will probably use signal (pulse, sawtooth, triangle, and sinusoid) tables stored in flash memory. EEPROM memory is too small to store all signals, but I will use it for last configuration storage that every time you switch that generator, the previous settings would be loaded. And I still didn’t decide what language to use for programming the device. C would be much easier and faster, but I will lose speed. The maximum signal frequency would be much lower than using pure ASM. But ASM programming takes much more time to implement. Any comments while I will be assembling the box?
