I'm working with a custom board using an nRF5340 and NCS v2.7.0. The UART3 peripheral is connected to an ISOW1412 isolated transceiver and is configured with RX assigned to P0.22 and TX to P0.20 (the other UART peripheral addresses are being used by other devices). For right now, all I'm trying to do is perform some sanity checks to verify that there aren't any critical board mistakes, so I'm using part of the source code from the UART lesson of the nRF Connect Fundamentals course just to transmit 2 test bytes (shown below for reference).
/* STEP 8 - Register the UART callback function */
ret = uart_callback_set(uart, uart_cb, NULL);
if (ret) {
return 1;
}
/* STEP 9.2 - Send the data over UART by calling uart_tx() */
ret = uart_tx(uart, tx_buf, sizeof(tx_buf), SYS_FOREVER_MS);
if (ret) {
return 1;
}
The project builds and runs fine, but anytime I attempt to transmit data, I've noticed that the TX line is never pulled down. My callback gets called for the UART_TX_DONE event, so I'm not sure what or where the issue is.
Some additional information:
- UART2 is currently being used for logging. When switching UART2 and UART3 (so UART2 connects to transceiver and UART3 is used for logging), the board behaves in the exact same manner - logging works normally, and now the TX line of UART2 is held high. This leads me to believe the issue is not with the specific UART instance.
- When I configure the TX pin (P0.20) as GPIO output, I'm able to manually pull it down, so I'm also lead to believe that this isn't a hardware issue.
- Explicitly enabling NRFX_UARTE3 in my prj.conf had no effect (I don't know if this is important/relevant).
Is there something I'm missing?
Any assistance is greatly appreciated!