How to implement UART over USB on nRF52840-DK

[cpeng]

Hi I found one example project named "serial" that implemented UART over USB:

https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v15.3.0%2Fgroup__nrfx__saadc.html&cp=5_1_6_9_0_28_1

There are 2 USBs on nRF52840-DK board, USB J2 and J3.

J2 goes to ARM processor, J3 goes to Nordic chip nRF52840.

This project implement UART over J2.

My company will not put ARM processor on out product, only Nordic chip nRF52840, which means I need to implement UART over J3.

Is there any code that implements UART over J3 directly?

PS: there's another example project named UART, what's the difference of this one compared to "serial"?

[Jørgen Holmefjord]

Hi,

You are looking for the USB CDC ACM Example. There is also USBD BLE UART Example, which implements Nordic UART Service over BLE, and uses NRF_USB to transfer data to/from a serial terminal.

The example named 'uart' implements the old app_uart library, while the example named 'serial' implements the newer nrf_serial library. Both use the hardware UART peripheral, but they are higher layer libraries running on top of the UART driver.

Best regards,
Jørgen

[RMV]

@Jorgen Holmerfjord

I don't understand why Nordic cannot get its act together in terms of documentation. All the web pages and documentst that I have reviewed leading up to this response seem to indicate that the "nrf_*" API are to be deprecated and developers are advised to move to "nrfx_*" API functions. But your reference to "nrf_serial_library" seems to go back in time....

Please clarify. This has been such a nightmare for two weeks, trying to get a handle on UARTs as a newcomer to the Nordic ecosystem.

[Jørgen Holmefjord]

RMV: I'm talking about nrf libraries in my answer. There is no nrfx replacement for libraries, this only applies to nrf_drv drivers in nRF5 SDK. 

Even though the documentation refers to the old driver APIs as "legacy", as far as I know, there is no active plan to remove these APIs in nRF5 SDK. In fact, the documentation states that for some drivers, migration to the nrfx APIs is not even possible (at least at this point). Please see this answer for more details and discussions around this.

[RMV]

Thanks for the updates.