After correcting a few wiring errors, the single-channel vector generator works, though it needs some calibration. I have the vector generator on my test bench with the Silicon Labs EFM32WG starter kit (ARM Cortex-M4F microcontroller) running the firmware, and a mixed-signal oscilloscope on the floor showing waveforms. I’ve taken photos of the oscilloscope showing full scale (±0.5V) vectors, rising and falling. The rising ramp starts around -0.5V as expected, but doesn’t make it quite all the way to +0.5V, so I need to either tweak the R108 pot (ramp rate) or adjust the pulse width controlling analog switch T2. The falling ramp only starts from about +0.3V, and I’m not sure why. When I check everything statically the full DAC swing does drive the output to ±0.5V.
Now it’s time to wire up the Y axis, and maybe Z (intensity). Z isn’t necessary for basic functionality, but would be nice to have. I may skip it for now. Once I have Y going, I can put the scope in X-Y mode and see real vectors.
It’s also time to start thinking about laying out a PCB. The breadboard prototype was laid out for ease of assembly and debug, not for signal integrity, so a lot of noise is getting into it.