Can't transmit using UART

[juanignaciotroi]

Hello. I am starting a new project in which I need to communicate via UART. (I am develping with FRDM-KE02) I have tried to use the ConsoleIO provided by Processor Experto and used just the instruction "printf", I can't see any pulse train in my osciloscope when watch de PTA3 pin (Tx) in it.

I attatch the images of the configuration:

Thank you very much

[Jorge_Gonzalez · Accepted solution]

Hello Juan Ignacio Troisi:

There are some similar questions in the community:

Cannot toggle over PTA3 in FRDM-KE02Z

UART0 not working with KE06

UART0 not working with KE06

So the pins are true Open-Drain outputs.. External pull-ups are required to get a UART signal.

Best Regards!
Jorge Gonzalez

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

[juanignaciotroi]

Hello. Thank you for your help but I couldn't solve this problem yet. As adding pull up resistors didnt work, I have tried by configuring an AS component so that UART0 is asociated to pins PTB0 and PTB1. However, I still can't see anything different to 0V when trying to watch the Tx pin in my oscilloscope.

Here is a link with my project: Dropbox - asin ​. Maybe there is an error in software which I didnt detect.

Thank you very much

Juan Ignacio

[Jorge_Gonzalez]

Hello Juan Ignacio:

Sorry I just noticed that in FRDM-KE02 there is something else to consider. If you are measuring in the header pins then in the schematics you can see that there are some resistors not populated by default:

So to watch any of these signals on the header you need to solder 0 ohm resistors or simple solder joints, as well as removing the alternative function 0 ohm resistor.

Regards!

Jorge Gonzalez