Can i invert the Rx,Tx UART signal?

Hello Guys,

I am using colibri imx7d with uart5.
Linux image: Linux colibri-imx7-emmc 4.1.44-2.7.4+gb1555bf.

We have used MAX3225E(RS-232 Transceiver) in our design, which has a inverted output.
We have connected it to uart5. But the output signal of MAX3225E is inverted.
Is there any way to invert the output signal in the driver?

hi @abhilash

Could you provide the hardware version of your module?
Which carrier Board are you using?
Which SODIMM Pins are you using for the UART5? Could you share a connection diagram?

Best regards, Jaski


I am using V1.1A, imx7d with emmc.
We have designed our own carrier board.
I have attached the schematic.


I believe from the i.MX7 reference manual that you can invert RXD and TXD, however RTS/CTS can not be inverted.

Compare with registers UARTx_UCR3 (INVT) and UARTx_UCR4 (INVR)

Your schematic does not look like you would need an additional inverter. E.g. in ‘idle’ you will get a ‘1’ at Colibri TXD, this goes uninverted trough your isolation and the MAX3225E inverts the signal to ‘-5V’ which is what you would expect.


Hi @max.tx

My bad , this is expected from the circuit.