Invert UART TX Signal

[Marcio Segura]

Good day, I am using a USB to UART IC and it isn't working just because the nRF51822 Tx signal is inverted from this IC. There are some way to invert the UART signals?

[Joe Merten]

Hmm, I'm not really sure where your problem is located.

We have to distinguish between Uart at TTL level (which is found directly at the pin of the nRF51822) and the Uart RS232 voltage level behind the driver (e.g. Max3222). They both are different in there voltage level and also inverted against each other (all signals: Rx, Tx, Rts, Cts …).

E.g. when the Uart is idle (not transfering data), we see a high level at the nRF51822's pin but a negative voltage behind the driver chip.

For me, as I'm using the nRFgo Starter Kit, RS232 communication was never such problem.

[Joe Merten]

You may show the code fragment of your uart configuration (using Sdk's simple_uart?) Even your Makefile is relevand (for something like BOARD := BOARD_NRF6310). Which nRF51822 hardware are you using (e.g. nRFgo or custom HW)? Have you tried to run the Sdk's uart example code?