MSP430FE427: UART TX waveform abnormal

Hang Yang

Part Number: MSP430FE427

Tool/software:

Hi Experts,

My customer is having issue using the USART as UART. They transmit data continuously in a loop but saw the following waveform at the TX pin.

Looks like that the TX pin is not able to drive low. But it can output low when configured as GPIO.
Any idea what might be the cause?

Regards

Hang

22 days ago

0 Keith Barkley 21 days ago

Guru 37035 points

If this is a launchpad, make sure there is nothing else on the pin.

0 Hang Yang 19 days ago in reply to Keith Barkley

TI__Intellectual 1431 points

Hi Keith,

This is a custom board. The pin is only connected to a PCB trace, we probed the signal right on the pin.

Regards,

Hang.

0 Hang Yang 18 days ago in reply to Hang Yang

TI__Intellectual 1431 points

Hi Keith,

I have the project from customer, is it possible to try it on your side and on Launchpad? We don't have this LP on the site. If this can run on LP, then it should be the issue on customer board.

Regards,

Hang.

0 Keith Barkley 18 days ago in reply to Hang Yang

Guru 37035 points

I don't have that launchpad.

Are they using GPIO commands to force the pin high?

Is it by any chance an open-collector output? try putting 1K on it.

But it is always a good idea to pare down the example to a small working version and post it here - often you find the reason it isn't working via that process!

0 Zoey Wei 17 days ago

TI__Expert 4410 points

Hi Hang,

Do you have customer's demo code?

Regards,

Zoey

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MSP430FE427: UART TX waveform abnormal