On the other hand, if the ClearFog is powered on when the console USB cable is plugged in, the ClearFog will boot as normal. It is possible to interrupt the boot if desired, and if left alone it will autoboot.
How can we autoboot the ClearFog even if a cable is not plugged in? It is almost as if when the cable is not plugged in, electrical noise causes phantom key presses to interrupt the ClearFog’s boot.
This is not an issue I have heard about before. Perhaps your SOM is not fully seated and you are getting noise on the UART lines to the SOC? You can try re-seating the SOM to see if it is a mechanical issue. If you just want to overcome the issue in software, then you can configure u-boot to require a specific keypress to break the boot sequence rather than any key. This should also work around the issue you are seeing.
Thanks for your help. I’ll give it a go once I have some time. As a workaround I’ve plugged a cable from the ClearFog’s console port into a spare USB port on the ClearFog, but won’t be able to depend on it forever.