Today's tasks:

1. Configure DAC: make sawtooth wave
2. Configure op Amp as c2v converter
3. Choose GPIO and output 100 Hz and 158 Hz square waves
4. Start designing IR receiver circuit

Configuring the DAC wasn't hard, but with the Curiosity board there's a gotcha. Pin RA0 (DAC1 output) has some kind of load (edit: an LED is attached) on it. The DAC is simply ramping up/down using the DAC1CON1 register. With several tries I only reached 2.0 volts at peak (you can see in column B). 

Eventually I pulled just that pin out of the socket and this is the nice signal, exactly as expected.