1 year ago.

Disabling UART Instance at compile time.

Is there a configuration setting for the NRF52 in the targets folder or targets.json, where I can disable the UART interface at compile time. i,e, when I build my application using mbed-cli can I turn off this feature. Currently in my application I do call a method to disable the UART, however I am not sure if this takes effect, once the application is running even though its the very first line of code, in my application.

disabling UART

#include "nrf_uart.h"

int main() {

Thanks, Ajay.

Question relating to:

The nRF52 Development Kit is a single-board development kit for Bluetooth Smart, ANT and 2.4GHz proprietary applications using the nRF52 Series SoC. This kit supports both development for nRF52832 SoCs.
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1 Answer

1 year ago.

Hi Ajay,

You shouldn't have to manually disable the UART, but if you do want to remove the UART capability you can modify the targets.json file for the MCU_NRF52832 target. You will want to remove the following from the "device_has" list:

  • "SERIAL",
  • "SERIAL_FC",

We haven't tested that ourselves so hopefully that won't cause a problem.

Additional information on target configuration is available here:


Ralph, Team Mbed

Thanks a lot Ralph for taking the time to respond. I will give what you have suggested a shot.

After looking at the mbed-os 5.5.4 I noticed that in the file mbed-os\targets\TARGET_NORDIC\TARGET_NRF5\TARGET_MCU_NRF52832\sdk\nrf_drv_config.h has the following #define

  1. define UART0_ENABLED 1

would setting that to 0 disable the UART0 instance?

Thanks, Ajay

posted by Ajay Kashyap 27 Jul 2018

Hi Ajay,

Newer SDKs don't have nrf_drv_config.h but I revisited Mbed OS 5.5.4 and defining UART0_ENABLED to 0 will prevent Mbed from building. Likewise, removing the three features from targets.json we called out above also will prevent Mbed from building due to some test infrastructure that utilizes the serial interface. Unless you are enabling the UART or using the serial console for printf() the UART will be disabled.

posted by Ralph Fulchiero 31 Jul 2018

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