nRF SDK UART peripheral

[JPSvanderWalt]

Hi I am new to the SDK and I am working through the examples.  I am currently looking at the UART example under examples/peripheral. Iam seeing that both the virtual comm port and UART on P0.06 and P0.08 is doing the same thing.  I am struggling to see where I can turn of either the virtual comm port UART or the UART on P0.06 AND P0.08.  Also the activation of instances is somewhat confusing to me.  Can someone explain to me what needs to be activated in the sdk_config.h to have only one uart active at a time?

[awneil]

JPSvanderWalt said:

Iam seeing that both the virtual comm port and UART on P0.06 and P0.08 is doing the same thing

Not sure what you mean by that.

The virtual COM port is what connects the nRF chip's physical UART (on pins P0.06 and P0.08) to the PC - so that you can interact with it using  a terminal - so they will necessarily be "doing the same thing" ?

          PC                                           Dev Kit
  +-------------------------------------+         +-------------------------------------+
  |                                     |         |                                     |
  |    ............      ............   |         |   .............      ............   |
  |    :          :----->:          :   |         |   :           :----->:          :   |
  |    : terminal :      : virtual  :   |   USB   |   : interface :      : nRF52840 :   |
  |    :   app    :      : com port :<===============>:   chip    :      :          :   |
  |    :          :<-----:          :   |         |   :           :<-----:          :   |
  |    ............      ............   |         |   .............      ............   |
  |                                     |         |                                     |
  +-------------------------------------+         +-------------------------------------+
  

[JPSvanderWalt]

Thank you for clearing that up.  I understand that I can select any GPIO to create another UART.  Are there any examples to do this or is it documented in the user manual?

[awneil]

You can't "create" a UART:  the  UARTs are part of the chip hardware - so the number is fixed (although you can emulate a UART in software - by bit-banging).

The nRF52840 has two UARTs - you can use them both at once. How to configure what pins are used is described in the Product Spec under 'Pin Configuration':

https://infocenter.nordicsemi.com/topic/ps_nrf52840/uart.html?cp=4_0_0_5_32_1#concept_dly_2sw_sr

https://infocenter.nordicsemi.com/topic/ps_nrf52840/uarte.html?cp=4_0_0_5_33_7#concept_wmv_f2m_wr

The nRF52840 also has USB - so you could implement a virtual COM port on the chip's USB:

https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.0.0/usbd_ble_uart_example.html

[JPSvanderWalt]

Thank you very much.  Yeah, I meant emulating an UART with software.

[awneil]

"soft" UARTs are a last resort.

As the nRF52840 has 2 UARTs, you wouldn't want to do that unless you need 3 (or more) UARTs ...

I don't know if Nordic have any soft UART example, but there have been forum posts on the topic before...