nRF9160-DK USB serial broken if USB not connected before boot

RE: nRF9160-DK USB serial broken if USB not connected before boot

Kenneth — Wed, 04 Dec 2019 08:15:42 GMT

It is intentionally this way, have been for most (if not all) nRF SDK out there. It could be very problematic if the SEGGER chip claimed two pins if they were used for other purpose in the application.

Kenneth

RE: nRF9160-DK USB serial broken if USB not connected before boot

Jonathan — Tue, 03 Dec 2019 15:28:13 GMT

So ... is that something your secure_platform_manager should do when compiled for the PCA10090? Should I check if there's a newer version available?

RE: nRF9160-DK USB serial broken if USB not connected before boot

Kenneth — Tue, 03 Dec 2019 14:38:04 GMT

Typically all IO's are considered generic, and the SEGGER chip that is the UART-USB bridge will not take control over any pins (e.g. set correct level for UART) until the COM port is opened no.

RE: nRF9160-DK USB serial broken if USB not connected before boot

Jonathan — Tue, 03 Dec 2019 13:38:00 GMT

As I'm using the official Nordic nRF9160-DK (PCA10090 v0.8.2), I didn't expect to have to add various pull-ups or pull-downs to get the serial port to work.

Can you confirm that you're stating there is a hardware issue with the nRF9160-DK? Do you know if a later version of the board resolves this issue?

RE: nRF9160-DK USB serial broken if USB not connected before boot

Kenneth — Tue, 03 Dec 2019 13:22:53 GMT

Have you made any progress?

I would expect some of the UART input pins (CTS or RXD) is floating and causing the code to fail, could be either of the com ports (application or modem). If you have the possibility to measure those pins before open com port and after a reset I would expect you would find the problematic pin(s). Maybe they need to be pulled high/low to avoid them floating in such case.