Enviro+ FeatherWing fails to produce 5V until power-cycled

[kjw]

I just turned on an Enviro+ FeatherWing and noticed my PMS5003 wasn’t responding. I’m running essentially the Pimoroni CircuitPython library for this on a (healthy) Feather nRF52840 Express. I noticed as it was enabling that my cheap, inaccurate USB power meter went from 0.01A to 0.03A. I’d normally expect around 0.10A if it was running. I measured the VCC voltage on the PMS5003 picoblade lead and it was 0V. I ran the code several times to no avail. I also pressed the reset button on the FeatherWing and that didn’t help. In the end I power-cycled it by unplugging USB at host and suddenly 5.004V appeared on VCC.

Is there anything intentional on this board that can stop that 5V supply? This is the first time I’ve noticed this despite doing a lot of work with this combination recently.

[kjw]

I think I had this again today, the PMS5003 didn’t burst into life on the first power-up of the day using normal power from USB into the Feather nRF52840 Express with Enviro+ FeatherWing stacked on top running plotters_combined example code.

I didn’t bother unplugging it to check 5V but here’s a view from a logic analyser which matches what I previously observed. The Feather RX line stays at 0V which seems indicative of this issue.

Here’s the first 25 seconds with power-on:

Here’s the program being restarted at REPL:

A power cycle seems to be the workaround.