Is MXP UART.RX 5v tolerent

[JohnGaby]

Is the UART RX pin on the MXP port 5v tolerent? In other words, can I safely connect the TX from a 5v Arduino to that line, or do I need a level shifter?

Thanks.

[Joe Ross]

Yes, per the specifications: https://decibel.ni.com/content/docs/DOC-30419

[JohnGaby]

Yes, per the specifications: https://decibel.ni.com/content/docs/DOC-30419

Are you sure about that. I cannot find anything in the spec you referenced that addresses this issue (perhaps I am missing it?), only a comment down below. Also there is another comment stating that the UART on the MXP is 3.3v TTL.

The thing that worries me is that it is documented that the RX pin has a 40K pull up resistor to 3.3v, and it indeed seems to be pulled up to 3.3v when I look at it on a scope. What happens then when I try and drive it to 5v with and Arduino?

Thanks.

[Joe Ross]

Sorry, it's spread across two documents. In the User manual, page 9 it says that the MXP uart are electrically the same as DIO lines.
In the specifications, it shows that DIO are 5V compatible input.

If you have further confusion, I'd suggest asking NI.

[JohnGaby]

Ok, I see it, thanks.

[JohnGaby]

For anyone else who might be hesitant to try this, I went ahead wired the RoboRio's RX to the Arduino's TX and both functioned as expected and I was able to transmit data across the serial line.

Thanks for your help.