Quick update on the OPQBox2. So far I have tested the ADC and UART. UART is behaving as expected, and I added some python test to Github, to test perform UART loop-back when testing a freshly assembled board. The ADC..... the ADC is very complicated. I did manage to get it running, but only in polling mode. DMA mode should be much faster.
I made a small mistake in the design of the battery power switch-over circuit. I laid down a MOSFTET which switches the power from the battery in case of a blackout backwards. This caused the body diode to conduct and effectively create a short between the battery and the 5V ACDC supply. There is an easy fix, I just flipped the SOT-23 upside-down and rotated it. Its not pretty, but its secure and it works. Will have to fix it for the production
I decided I will be developing firmware for the OPQBox using a test driven methodology. Firstly I really need to develop better testing habits. Secondly OPQBox2 is a self-hosted system, the PI can compile both its own code and the DSP code as well. The in-system programming allows us to flash the DSP with the firmware required for the test, while keeping the operator out of reach of the 120V AC. Finally if we even need to test 100 OPQBox2 boards, a modular, well developed testing framework will be invaluable.