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CCS/TM4C129XNCZAD: Junk datas are getting

Chandana KV
Intellectual 740 points
Part Number: TM4C129XNCZAD

Tool/software: Code Composer Studio

Hi,

I am using dk tm4c129xnczad controller.Here i have tried uart demo program which is working through usb cable and i am able t read the data in dock light software using usb cable but i want to read the data using usb to serial converter cable if i connect this cable i am getting the junk data.so i am not getting where is the problem i have connected 2nd pin of rs232 cable  which  is rxd pin to tx pin (PA0)  uart0 of the controller and vice versa but still i am facing the same issue.Can you plz tell me  what could be the problem or do i need to write any other protocol program for usb to serial cable.

  • 0
    TI__Guru 72500 points
    The problem is most likely hardware. First, PA0 is U0RX (an input). PA1 is U0TX (an output). Second, what type of USB to serial converter cable did you use? PA0 and PA1 are 3.3V digital signals (3V for a 1, 0V for a 0). RS232 is -25V to -3V for a 1 and +3V to + 25V for a 0. Connecting an RS232 signal directly to the digital pin PA0 may destroy that pin. There needs to be an RS232 transceiver between them. There are some USB to serial cables that provide compatible levels. You need to make sure that your cable is compatible with 3.3V logic or add the appropriate transceiver. Did you remove the jumper plug from J3 marked PA0? You cannot successfully have two different devices trying to drive PA0, the UART0RX pin. See the schematic in the User's Guide to see how PA0 and PA1 are used on the DK-TM4C129x board.
    www.ti.com/.../spmu360a.pdf