UART over standard drive, low frequency I/O only GPIO pins

[Prasad]

On a nRF52833 on a custom PCB, due to space and allocation limitations, I need to run UART Rx and UART Tx over GPIO pins that are limited to standard drive, low frequency only. On the QFN40 package, the pins under consideration would be P0.03, P0.02, P0.28, P0.29, P0.30.

In this configuration, I have the following questions:

1. To adhere to the low frequency requirement, I was planning to use baud rate of 9600 at max. Will that satisfy the < 10kHz requirement?
2. Is there an impact to RF performance when there is simultaneous RF & UART communication when (1) is satisfied?
3. For FCC compliance testing, would the Upper tester (as referenced here https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v12.2.0%2Fble_sdk_app_dtm_serial.html&cp=4_0_1_4_4)  support 9600 bps?
4. Would standard drive be sufficient to communicate with the tester in (3)?

Thank you for your help,

Prasad

[Kenneth]

1. Yes, that is fine.

2. No.

3. You can still use default 19200baud for DTM, since the UART is inactive during test, it is only used to start and stop test.

4. Yes.

[rolandash]

Some extension to the original question:

1) though a 921000 bps rate UART tx/rx should not use these pins around radio path, but cts/rts signal should be OK to be assigned to these pins?

2) the CS signal in a SPI connect is also OK to be assigned to these pins?

3) if an external PA (i.e., nrf21540) is connected to 52833, the TX_EN/RX_EN signal should also be fine to be connected to these pins near radio path?

Thank you.

/Roland

[Kenneth]

All yes.

Kenneth