How to communicate with PIC microchips with UART ports in tx1

Recently, I need to communicate with two PIC microchips with two UART ports in tx1, but it doesn’t work when I connect their ports. I feel the UART ports in tx1 doesn’t work . I want to know if I need some settings to tx1, and how to set?
Really hope someone can help me.
Thank you

The J21 UART port is already bound as a serial console. To use it for anything else would require disabling it in both U-Boot and the Linux kernel…then it would be free to use as ttyS0 under the usual driver, or ttyTHS0 under the NVIDIA DMA-capable driver. By default it is just an 82550 emulation since U-Boot does not have the DMA version.

J17 also routes to the camera header, and if you are not using a camera, this will “just work”. This is configured as “/dev/ttyTHS2”.

I have not looked at the other ports.

The method for changing device tree differs in R28.1 versus older versions of L4T. In all cases if a port is tied to some other function, then you’d have to be sure the other function is disabled first. For example, I believe that bluetooth ties up one UART…in that case you’d need to disable bluetooth prior to trying to configure the port to use for your own purposes (I don’t know which pin that would be).

For testing I advise wiring together the port’s own TX and RX in loopback and seeing if TX echoes back on RX…you’ll be guaranteed that the port setup of TX will match RX…whereas if you used a separate UART then you won’t know for certain that a failure is not caused by both ports having different settings.

If you have an oscilloscope you might also monitor to see if there is traffic on the TX during data copy. Keep in mind that if flow control is enabled, and if flow control does not allow traffic, then you won’t see anything even if the port is working correctly.

Thank you very much for your reply, however I find that the program in microchip has something wrong.And when I solve the problems in microchip, the communication succeed. Thank you very much.