nRF Connect Direct Test Mode re-connection issue if you remove the debugger

RE: nRF Connect Direct Test Mode re-connection issue if you remove the debugger

Kenneth — Mon, 30 Mar 2020 13:56:57 GMT

Hi,

If you search for nrf_gpio_cfg_input() in nrfx_uarte.c and nrfx_uart.c you should be able to replace NRF_GPIO_PIN_NOPULL with NRF_GPIO_PIN_PULLUP for the RXD pin (which I suspect is the problematic one).

Best regards,
Kenneth

RE: nRF Connect Direct Test Mode re-connection issue if you remove the debugger

Branden Sheffield — Thu, 26 Mar 2020 19:38:09 GMT

Thanks for the suggestions! I like those ideas, I don't have space on my custom HW to add the 10ks but could probably modify my debug boards easily and test this. I may try the suggestion to add the reset command in the uart error handle first however as a quick work around.

thanks again for the quick feedback!

PS - I still think a reset feature may be nice the DTM app as a future feature request 🙂

RE: nRF Connect Direct Test Mode re-connection issue if you remove the debugger

Kenneth — Thu, 26 Mar 2020 11:58:37 GMT

I suspect there is an assert occurring here due to noise on the UART lines, this will cause UART framing error. In the uart_error_handle() I can see that the DTM application will assert by default if there is APP_UART_COMMUNICATION_ERROR. In addition I suspect that app_error_fault_handler() is configured with DEBUG enabled, thereby it will not execute NVIC_SystemReset().

I guess there are several workarounds possible here, for instance you can in the uart_error_handle() simply call NVIC_SystemReset() directly if there is an APP_UART_COMMUNICATION_ERROR.

Alternatively you may also look into adding external pull up resistor (e.g. 10kohm) on the UART RXD and TXD pins to avoid the APP_UART_COMMUNICATION_ERROR to occur in the first place.

Best regards,
Kenneth