I'm working with custom boards using the nRF9161 chip. In the process of trying to test the layout of my custom board, I was able to successfully connect to and flash the device. After connecting to and flashing the device several times, I've lost the ability to connect to and flash the device, and I'm trying to figure out if there is a way to save the boards or if they're just lost. From what I've researched and read online, it seems likely that the issue was at least partially related to improper handling of the nRESET pin, but I'm still not entirely sure what happened. The nRESET pin was driven low multiple times on each board (it is controlled by an external MCU), and may have also been incorrectly driven high at 3.3V as a part of my initial testing (I know now that it shouldn't be driven high at all, and should simply be held at 2.2V by the internal pull-up).
Here's the current state of the boards:
- I can tell that they are still running the last code that I flashed them with, because I had them configured to blink an external led as part of the program.
- The SWDIO pin on the boards is LOW. Based on what I read online, it seems like the SWDIO pin should be held high by an internal pullup.
- I cannot in any way connect to the boards or get them to be recognized by my computer / J-Link. I've tried disconnecting/reconnecting the boards, using nrfjprog commands like --recover and --eraseall, but the debugger application isn't able to properly communicate with the target.
Are there any next steps I should try? I know from reading the documentation that the nRESET pin can affect access to the Debug Access Port and the behavior of the SWDCLK and SWDIO pins, but I'm not sure if the SWDIO pin being held low is a sign of the DAP simply being locked/inaccessible, or if it is a sign that something inside the chip has been damaged. Besides the nrfjprog commands, is there another way to restore the DAP to its default settings?
Thanks in advance for the help!