Mon May 19 00:43:58 EDT 2014

R/2R ladder DAC for PIC18 function generator

I wonder, how fast can data be sent over a PIC18 port?  For a function
generator, a DIY R/2R ladder might be good enough.

If data is from ram and we have dedicated operation, probably 2 cycles
per sample.  A sawtooth can be done faster by just incrementing the
port register.  That would be a nice hack for a fixed frequency
function generator, but then a counter would be good enough.

Maybe this can be used as a shepard tone generator?