Sinewaves using interrupts.

[mark_s]

Hi Hank,

Note that the avr project needs at least 8 I/O pins to drive the resistor ladder(DAC). So with a PIC12f series you are stuck using PWM, serial DAC or a dedicated DDS chip.

I tried a spi DAC, too slow. Couldn't get over 600hz. It wouldn't be too hard to do the avr dds with a pic. Use a look up table and a loop and write each value to an 8bit port. Not sure how the speed would compare with an AVR?

This is the best, but it is expensive
http://www.sparkfun.com/products/9169

I wrote some code for this in PBP if you are interested.

cheers

[HankMcSpank]

Hi Mark,

Agreed about the 12lf1822's 6 Inputs & 5 outputs being insufficient for a resistor ladder ...I therefore have three options...

1. Use HPWM
2. Use the 12lf1822's internal 5 bit DAC (which while woeful, is handy from a low parts count & convenience/learning perspective)
3. Go with a larger 14 pin sibling (eg 16lf1824) & use a reistor ladder.

As much as I'd really like to just use the dedicated DDS chips, but they're way overkill for my modest needs, too expensive & also I'd like to lean how to roll my own so to speak.

Just sounding the ground again here.