No UART Tx on one pin using Processor Expert

[mrentz]

Hi all,

I'm new to KDS and processor expert and I'm trying to get the UART working on a new design. I can't seem to get the UART Tx to work on one of the available pins (PTA3) but I can if I mux it to the other possible pin for that peripheral (PTB1).

When I run the code the pin always stays logic low when using PTA3. If I just change the pin muxing using the hardware configuration tools it works fine on PTB1.

Receiving works fine using the PTA2 port so it seems I've set it up correctly.

Has anyone else seen something similar or maybe could give some pointers on how to troubleshoot this?

MCU: MKE06Z128VLH4

KDS version: 3.2.0

Debugger: Multilink Universal FX

[mrentz]

Hi Alice,

Thanks for your response.

It is a custom board and the UART is set up similar to what you have. I've now tried your project with no luck. I've also tried another chip with no success.

The weird part is that I can get the Rx to work with the settings I'm using and Tx works on PTB1. I will try to build another board tomorrow with only the necessary components to see if something is causing the pin to malfunction.

[Jorge_Gonzalez · Accepted solution]

Hi Matthew,

You might be missing a pull-up resistor. PTA3 is a true open-drain pin as output as noted in the manual:

So you need an external pull-up resistor to get a signal.

Regards!

Jorge Gonzalez

[mrentz]

Jorge,

Yep that would be it. Not sure how I missed it in the datasheet. That's what I get for "rapid prototyping" lol.

Thanks for your help.

[Alice_Yang]

Hello ,

What about your board, the custom board or demo board FRDM-KE06 ?

I test on FRDM-KE06, UART0, the TX-PTA3 can work well , i also attached my project.

If you also use this board , please be sure R47 and R39 is connected (be default this is disconnected).

If you use the custom board , could you please change another chip to have a try .

Have a great day,
Alice Yang

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