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EVM430-I2040S: EVM430-I2040S Communication Issues with the PC

Kou Miyazawa
Prodigy 40 points

Part Number: EVM430-I2040S

I am using the “EVM430-I2040S” and am trying to communicate with a PC via a D-sub connection.
When I send a 1-byte data, the PC receives incorrect data (data that appears to be bit-shifted)—for example, when I send 0x35, it receives 0x20; when I send 0xaa, it receives 0x00; and when I send 0x03, it receives 0x02.
Do you know what might be causing this?
Thank you in advance.

  • 0
    TI__Mastermind 27350 points

    Hi Kou,

    Have you done a loopback and are you scoping the communication lines with a logic scope? If it was a single bit shift then 0xAA should return 0x55. Getting all 0's seems to be a different type of communication error, could be timing related issues.

  • 0
    Prodigy 40 points

    I was checking the waveform with an oscilloscope.
    As it turned out, it was a hardware issue.
    I found that at speeds of 115,200 bps or higher, the waveform begins to distort and sometimes becomes unreadable.
    Thank you for your advice.

  • 0 in reply to Kou Miyazawa
    TI__Mastermind 27350 points

    Hi Kou,

    If the signal starts to look like shark tooths instead of square waves, then you have too large of an RC. You can apply pull-ups on the UART lines to allow for faster response time.

    Depending on the related ICs, though they might be bandwidth limited. For example, the D-port cable or an RS232 transceiver may have a limitation of 9600 baud or 115200 baud.