nRF only mode only works sometimes

Question

Hello, 
 I am looking to run the ble_app_uart example from the SDK v17 in nRF only mode on the nRF52840 DK. When running the application as is on nRF only mode, it fails during the initialization phase and does not seem to enter the main loop. 
 However, when I set it up such that Rx and Tx are mapped to pins 1.14 and 1.13 so the DK communicates through UART to an external module, it is able to run on nRF only mode, but only if SW6 is on Default when I power the board on and then toggle SW6 to nRF only mode. 
 I am not sure why this happens, so could someone please explain this behavior? 
 In both scenarios, the board is powered via the J2 USB connector (the one on the shorter edge of the board) and SW9 is on VDD. 
 Thanks!

Jared · Accepted Answer

Hi, 
 I understand. The application is probably asserting due to the logging feature which uses RTT as backend which again is connected to the interface chip.This will cause the application to assert when the interface is powered down. You can try to remove the logging from the project. 
 regards 
 Jared

Jared · Answer

Hi, 
 nRF only mode means that the only the nRF IC is powered on the DK. The unmodified ble app uart example is setup so that it communicates through the P0.08 and P0.07 which is connected to the interface chip which again is connected to the J2 USB header. If you want to directly through the J3 USB header then you would have to use the USB ble app uart example instead. 
 regards 
 Jared

nRF only mode only works sometimes

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