Chelydra pcb

What?

CHELYDRA is a board-level electromechanical charge redistribution analog-to-digital converter, plus an accompanying controller implementation written in SystemVerilog.

It has an integrated reference voltage of 1.024 V, 4 bits of resolution, and a sampling rate of approximately 8 Hz. Communication with the provided controller is done over UART at a fixed baud rate of 9600.

How?

The PCB is simple and any commercial manufacturer should be able to produce it. It is designed such that it isn't too difficult to solder by hand. Components can be found in the included BOM. For the NPN transistors, I personally used the MMBT3904, but other transistors with the same pinout should also work. It is designed to operate at 3.3 V.

The provided controller is packaged in a Vivado project targetting an Arty S7-50. Hardware utilization is quite low, so it shouldn't be too difficult to port it to other boards or FPGAs.

Vivado likes to store absolute paths. In this repo the original paths have been modified so that they can be adapted after cloning. To do this, run the provided script ./specify_paths.sh, which will use the path where you have cloned the repo. To revert it to the original state, run ./generalize_paths.sh.

To start a single conversion, use a microcontroller or UART adapter to send 0x01 to the controller. To start free-running conversions, send 0x02 instead. At the end of each conversion, the controller will return the result also over UART. To stop free-running, send 0x00 and the controller will stop once the ongoing conversion is done.