Feature/pounder timestamping

[ryan-summers]

This PR implements timestamping using the external pounder SYNC_CLK to drive an internal timer. This addresses the IO architecture in #147 and the timestamping logic outlined in #170

This finalizes the asynchronous IO architecture and timestamp acquisition features.

These changes require a hardware revision of Pounder before they can be used:

• SYNC_CLK to Stabilizer ETR/CHx timer input sinara-hw/Pounder#76

TODO:

• Update documentation
• Feature/digital input stamp #195 should be merged
• [DMA] Next transfer returns number of remaining data stm32-rs/stm32h7xx-hal#173
• DMA buffer swap logic stm32-rs/stm32h7xx-hal#171
• Add feature for V1.1 pounder support (changes to DDS_Reset and SYNC_CLK pins)

Testing

I manually updated the process() function to record timestamps and calculate delays between each sample. Visual inspection showed a nominal 40 tick delay between each sample, where each tick corresponds to 32ns (1/4 of a 125MHz clock). Given that the ADCs were configured to sample every 128 ticks of a 100MHz clock, the delays of both clocks align to ~1.28uS/sample, which indicates that the pounder clock is correctly timestamping ADC samples.

[jordens]

Is there a way we can merge this without regression on existing v1.0 Pounders? Maybe this is the time for #[cfg(feature = pounder_v1_1)] or similar?

[ryan-summers]

Is there a way we can merge this without regression on existing v1.0 Pounders? Maybe this is the time for #[cfg(feature = pounder_v1_1)] or similar?

Yeah, that shouldn't be too hard. I'll add this to the checklist above.

[dtcallcock]

Given sinara-hw/Pounder#84 (comment), it's not clear that more than ~2 boards were ever made. If you already patched one to v1.1 and it'll be straightforward to do the other(s), it might not be worth it.

[jordens]

Given sinara-hw/Pounder#84 (comment), it's not clear that more than ~2 boards were ever made. If you already patched one to v1.1 and it'll be straightforward to do the other(s), it might not be worth it.

It's worth it for us.