nRF52840 Mini and Serial Print

fetcorp · August 22, 2019, 5:48pm

My apologies if I posted this to the wrong forum but it is a basic programming issue but specific to the new nRF52840 board I bought. I can get part of the BLE example code running (LED on/off control via tablet, but not PBswitch read) I can get standard Blinky example running, but I can not get a simple Serial.println(“hello”); working. I have done so successfully with several other arduino boards but not the nRF52. I need to test some of my SPI and I2C code with this ARM MCU and will need “printing” to help me debug the port. This works on a nano but not the new board.

Serial.begin(9600); // Serial is the USB serial port

Serial.println(“HELLO”);

Any help or suggestions appreciated.

El_Duderino · August 23, 2019, 7:31pm

Hi fetcorp,

If you are printing via serial during your setup, try adding in a while loop like this:

Serial.begin(9600);
  while ( !Serial );
  Serial.println("Ready!");
  delay(500);

That should fix the issue in setup. For debugging in your loop, Serial.println(); should work just fine. Let us know if you run into any other issues or cannot get your Pro nRF52840 Mini printing serial data and we can troubleshoot further.

fetcorp · August 25, 2019, 9:54pm

Hi,

Thanks for the suggestion, but it doesn’t work either. With a normal Arduino, I am connected to the MCU via a USB to Serial (Rx/Tx) FTDI chip, directly into the Rx/Tx pins of the Atmega328p MCU for example. With the nRF52840, there is a native USB 2.0 port on the MCU itself, so it is a direct connect. There are also assigned Rx/Tx pins on the MCU.

Given a normal Serial.println isn’t working with the nRF52840, is it possible that a Serial.println is being compiled to be directed out the Rx/Tx port instead of back up the USB connection?

I can’t think of why else something so basic as a “print” statement will not work.

Thanks in advance.

Jim

El_Duderino · August 26, 2019, 9:32pm

Hmm, well that is strange. I’m having no issues using the method I outlined in my previous post with a known good Pro nRF52840 in my testing so I’m not entirely sure what is going on here. Calling “Serial.print();” should route to the USB port since Serial1 is hardware serial and is routed to pins 17 (TX) and 15 (RX). You could try connecting those pins to a 3.3V FTDI or similar USB to Serial converter and see if you’re seeing the serial data there but I would be really surprised if that is the case.

Do you have the SparkFun board definition added into the Adafruit nRF package? There was a small issue that we fixed roughly a month ago related to using serial so if you installed the board definitions following the instructions outlined in our [nRF52840 Development with Arduino and CircuitPython Guide longer than a month ago, try going back through those steps and re-installing the Pro nRF52840’s custom board definition. Even if you did install them after the fix was pushed, re-installing the board definition may fix the problem for you.](https://learn.sparkfun.com/tutorials/nrf52840-development-with-arduino-and-circuitpython#arduino-installation)