LPUART Example on two connected MIMXRT1020 EVK boards

estacey · ‎01-06-2020

I'm running the lpuart interrupt driver example on two MIMXRT1020 EVK boards with common grounds and RX,TX from one board tied to TX,RX of the other. I'm trying to understand what is happening. I'm running debug sessions and putty terminals via the debug ports to both boards. One of the boards will take inputs via the terminal and both boards echo it back to both terminals, but the second board isn't echoing anything anywhere. It seems like the pins on the boards aren't even being driven, though I haven't hooked up a logic analyzer to know. How is the second board's terminal getting the data from the first board? I can sometimes get the second board's terminal to take data and cause triggering of breakpoints, but it isn't consistent across debug sessions and it isn't being echoed anywhere so I wonder what is going on.

Can I even operate two boards from the same PC with reliability?

I would appreciate any assistance in understanding how it is working.

victorjimenez · ‎01-09-2020

Hello Ellen,

The intended use of the lpuart_interrupt example provided in the SDK is to communicate the evaluation board with the PC. For what you are trying to achieve, you need to make some modifications in the application layer of the example, could you share the modifications you made?

Best regards,

Victor

estacey · ‎01-10-2020

I didn't modify the code. I simply tied the tx from the first board to the rx of the second board and vice versa. I ran the same example on both boards with two debuggers. Obviously, there are problems with the idea that you can drive data both with a terminal and with the pins. I changed now to enable UART2. It seems the debugger requires UART1 so my development will be restricted to one port. Am I correct in this? Thank you for your assistance!

victorjimenez · ‎01-14-2020

Hello Ellen,

You are correct, the on-board debugger UART is connected through UART1 interface to the RT1020. If you want to connect two boards through UART, you will need to use a different UART.

Best regards,

Victor