Serial output on the A311D?

I’m trying to figure out why the NixOS SD card I prepared for the A311D module isn’t booting, so I’ve hooked up a UART adapter to J18 for the first time ever. I’m not seeing anything during bootup, though, even when using the official SD card image. Are there any tricks or caveats when it comes to getting serial ouput from uboot on the A311D module?

I’m running:

sudo screen /dev/ttyUSB0 115200


Edit: I’ve just confirmed it’s not the UART adapters by successfully getting serial output from my IMX8MQ module.

Remember, that with imx8mq you get serial connection via uart on S1 while on a311d it is connector S2. This bit me several times already…



Thanks. Briefly considered deleting this thread because it seems like something I really should’ve caught, but I’ll leave it up in case someone else runs into the same problem!

This will also be documented in the Reform Handbook 2nd Edition: