David WhiteHare

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7 years ago.

How to properly do serial IO over pins P0.09 and P0.10 on the nRF52840-DK?

I tried this simple program:

#include "mbed.h"

Serial pc(P0_9, P0_10); // tx, rx

uint32_t counter=0;
int main() {
    pc.baud (9600);
    while (true) {
        pc.printf("%d, Hello World!\n",counter++);
    }
}

but it doesn't appear to send anything to pin P0.9.

Please advise.

ok, pin's 9 and 10 are problematic because of NFC. So, consider the same question with pins 7 and 8. In that case, it doesn't appear to send anything to pin P0_7 either.

posted by David WhiteHare 17 Sep 2018

1 Answer

Ralph Fulchiero
7 years ago.

Hi David,

On the nRF52840_DK you will have to use P0_6 for transmit and P0_8 for receive as these were selected for the board layout. We just answered your previous question on using Port 1 pins and included this reference:

Here you'll see that RX_PIN_NUMBER and TX_PIN_NUMBER are defined. Pins 5 and 7 are used for serial flow control.

-Ralph, Team Mbed

Hi Ralph,

It looks as though if I made the change: TX_PIN_NUMBER = p32, it would have the desired effect of making pin P1_0 be the Tx pin for serial.

Is there a way for me to create such an alternate PinNames.h file and have the cloud-based mbed use it during the compilation (substituting for the default PinNames.h file), our would I need to use a different, non-cloud compiler with isolated files to do that?

posted by David WhiteHare 18 Sep 2018

I've confirmed that mbed will serial print to pin P0.06 on the nRF52840-DK . However, most other nRF52840 modules don't have that pin exposed. Not even Nordic's nRF52840-DONGLE. So, it's important to be able to print to a pin other than just pin P0.06.

posted by David WhiteHare 18 Sep 2018