Attached is a project demo of the 10-bit dithered IDAC (DVDAC) analog for the PSoC4M. It is roughly follows PSoC5 DVDAC, described in the AB64275. Basically, it uses a DMA to dither the LSB of the 8bit IDAC at high speed, producing averaged pseudo-10-bit resolution.
The DMA transfer to IDAC on P4 is tricky, it has to be 2 bytes, with MSB set to 0x07, and LSB is actual IDAC value (so RAM array must be 16-bit instead of 8-bit). This MSB is configuration setting for IDAC, controlling current output/bit, which has to be set on each DMA transaction. The DMA trigger has to be set to "unknown width". Unlike PSoC5, on P4 DMA has no "nrq" signaling the end of Buffer transfer, instead the DMA internal irq and a PinLED are used to for that purpose. Those digital outputs and API callback are optional and can be deleted.
The project is not tested, but, I believe, should work.
Few notes:
1. The PSoC4 IDAC has barely 8-bit accuracy, it also prone to temperature drift, as it doesn't have an actual voltage reference. In a result, the DVDAC's INL absolute accuracy will also likely remain in 8-bit range.
2. To control the output, the Buck converter actually needs current injection into the FB pin, not voltage. So IDAC can be directly hooked-up to the FB pin without R1=10k resistor from Figure 1 (instead the upper resistor in resistor divider network is used). However, the IDAC in this mode must operate as a current sink, so for DMA transfer the MSB must be changed from 0x07 (source) to (?I don't know?) (sink).
3. A cheap external DAC, like 12-bit MCP4725, may be a better way to implement a DC-DC voltage control.
4. From my experience a digipot is even simpler way to control a Buck converter.
Figure 1. Project schematic.
