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USB to UART

Former Member

Hello,

 

     I'm working on a simple project to comunicate with an motorcycle ECU. I'm using a USB to UART will talk to the ECU, I know were the Rx and Tx pins are on the ECU connector, but I dont know which one is which. The ECU is fully poted. I am tring to avoid cutting the poting away to follow the traces. Is there a Way to determine whitch pin is Rx and which is Tx with a DVOM, or should I hook them up one way and if no communication  swtich wires? I was concerned about damaging the ECU or PC interface using the second method. The pc interface is a Silicone Labs CP2102 EK

  • 0

    Do you know the signal levels ?

    Is the ECU using RS232 levels of logic levels (3V or 5V).

    One of the signals from the ECU will be an input and high impedance and the other will be an output.

    If RS232 the input will be close to zero volts if unconnected and the output will idle at a negative voltage (-3 to -15V).

    If its a logic level interface the output will usually idle at +3 or 5V but this is not universal.

    You can check if a logic pin is input or output by attempting to pull it to the opposite state with a 10k resistor - this won't always work because you don't know what other ciruitry is in there !

     

    Michael Kellett

  • 0 in reply to michaelkellett

    I dot not know the signal level yet. I will check the ECU with a DVOM as soon as I can. The good part is the Racing ECU harness has a communication connector that has the RX and TX  and ground pin, so I can power the ecu easly to check voltage levels.  I may need a RS232 to TTL converter.  There is no labeling on the wiring diagram, for Tx,Rx