USB Game Controller with Raspberry Pi

Engineering 🇬🇧
ben-mcdonnell
2021-04-12
2026-05-01

  • ben-mcdonnell - 2021-04-12

    Hi,

    I have a Revolution Pi system that I would like to use a USB Joystick with to control a robot. It is a standard HID device that I can read with jstest. I have been testing with a PS4 controller for now, with the correct drivers installed.

    What would be the best way to interface that with CODESYS? I have seen a few other people asking similar questions on the forum, but I haven't seen any resolutions posted.

    Thanks in advance!

     

  • TimvH

    TimvH - 2026-05-01

    I'm not sure it will work, but you could try it with the CmpCharDevice library.

    You could create a function block that looks something like this:

    As input for the filename, you have to use your Linux device, e.g.:
    '/dev/input/event0'
    '/dev/input/by-path/platform-button@23-event'

    Off course you must also pass the pointer to the memory where the data can be written to and the size (count in number of bytes) of the buffer.

    FUNCTION_BLOCK FB_CharDevice
VAR_INPUT
    szFilename: STRING;
    pbyBuffer : POINTER TO BYTE;
    udCount : UDINT;
END_VAR
VAR_OUTPUT
    iState : INT := 0;
    nrBytesRead : DINT;
END_VAR
VAR
    xInit : BOOL := TRUE;
    dFlags: DINT := CmpCharDevice.ACCESS_MODE.O_RDONLY + DINT#4000; // see details for flags: http://linux.die.net/man/2/open, + DINT#4000 is for non-blocking
    hDevice: CmpCharDevice.CmpCharDevice_Implementation.RTS_IEC_HANDLE := -1;
    Result : CmpCharDevice.CmpCharDevice_Implementation.RTS_IEC_RESULT;
END_VAR

    IF xInit THEN
    hDevice := CmpCharDevice.CDOpen(szFilename, dFlags ,Result);
    // if it would not succeed, the result is -1 (Invalid handle)
    IF hDevice <> 16#FFFFFFFF AND Result = 0 THEN
        iState := 5;
    END_IF
    xInit := FALSE;
END_IF

IF iState = 5 THEN
    nrBytesRead := CmpCharDevice.CDRead(hDevice, pbyBuffer, udCount, Result);
ELSE
    nrBytesRead := 0;
END_IF

    Make sure you close the connection properly, maybe by overwriting the default FB_Exit method of the FB:

    // Clean up device
IF hDevice <> 16#FFFFFFFF THEN
    __TRY
        CmpCharDevice.CDClose(hDevice,Result);
    __CATCH
        ;
    __ENDTRY
    iState := 0;
END_IF
     

Log in to post a comment.