Testing UART on the Mallow Carrier board


I have written a QT project in VS Code that successfully opens a serial port on the SBC.

I would now like to test transmitting and receiving data over the UART using rs232.

I have two mallow carrier boards with the imx8m-plus on top.

My question is can I directly connect the two boards together over the UART1 pins(x19) and send and receive data.


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To test UART communication between two Mallow carrier boards with the iMX8M Plus modules, you can indeed connect the UART1 pins directly, but you must ensure proper cross-connection of the RX and TX lines between the two boards. This means the TX pin from one board should be connected to the RX pin of the other board and vice versa. Additionally, you might need to connect the ground (GND) pins of both boards to ensure a common reference point for the signal levels.

However, it’s important to note that the UART signals on the iMX8M Plus are TTL (Transistor-Transistor Logic) levels, not RS-232. RS-232 signal levels are different from TTL and connecting them directly without a level shifter could damage your boards. If your intention is to use RS-232 for communication, you would need an RS-232 transceiver to convert the TTL signal levels to RS-232 levels on both boards.

For a direct TTL UART connection, here’s a simple wiring guide:

  • Connect TX of Board 1 to RX of Board 2.
  • Connect RX of Board 1 to TX of Board 2.
  • Connect GND of Board 1 to GND of Board 2.

Ensure your software configuration on both boards is set to use the correct UART port and that the baud rate and other serial settings match. Also, remember to handle any necessary flow control in your software, if applicable.

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Toradex AI Assistant

Please, also check if these links can help you solve your problem:

UART (Linux) | Toradex Developer Center.

So since both SBCs use TTL levels I should be able to communicate with QSerialPort without damaging the SBC?

Hi @jojo ,

If you are just testing things on your bench, then jumping the “raw” TTL rx/tx together between boards shouldn’t be a problem. Note that this isn’t “rs-232” like you mentioned in the OP, so you really aren’t testing that (if that was your intention). You’ll need to insert some transceivers, protection circuitry, if you intend to do this over longer, noisier lines.

Also note that you’ll have to make sure no flow control is used (rts/cts/dtr/dsr), if you just intend to wire up rx/tx.

Thanks @DaveM for the reply.

My intention is to verify that I can send/receive data over the UART while running my software in a container on two SBCs.

I have verified the SBC(No Container) will send and receive data from my dev PC(Putty) with the cable below.

Yes, this is just bench verification.

Since connecting the two SBC directly together will not be an issue I’m going to move forward on verifying communications.

I will update the thread with the results.

Thanks you for you help.

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Hey @DaveM,

I was able to verify UART communications while using QSerialPort.

This has been solved.


Excellent…hope the rest of your project goes smoothly :wink: