KRC2Ed05 to Omron Safety PLC Serial Connection, Submit Interpreter stopping when transferring files

    I setup a serial link a few years ago (with much research on this forum) between my KUKA krc2 ed05 (KSS 5.6.need to check the rest) and an Omron G9SP safety plc which handles the robot cell safety, some critical functions (not ejecting the tool while the spindle is running, not releasing the ATC when the tool is not in the nest etc) and gives some additional IO. The serial communications is handled through the submit interpreter in the sps.sub file.

    It has been running well EXCEPT sometimes when I'm copying or moving large files between the usb thumb drive and the robot controller it hangs. After this I have to change to T2 (or T1), cancel the submit interpreter then start it again.

    I've included a copy of the relavent sections of the sps.sub file below (declarations and the actual code which runs within the main loop of the sps file). Some of the variables not defined here are defined globally in the config.dat file.

    I added the integer SerialDebug to find where it was hanging, and it's value is 14 so it's on the following line:

    Code
    WAIT FOR ($DATA_SER3 <> 0) ; wait for data in COM3 buffer

    I think basically the copying of large files messes up the timing of the serial port sending data to the Omron PLC. As such, the PLC doesn't respond. As such I'd like to add some sort of a timeout, so if nothing has been received in the COM3 buffer after say 500ms, it skips the receive data section and tries sending again. My first thought is to use a WHILE loop that also includes a small delay and counter to keep checking the buffer, and abort if it takes to long, but would like to know what best practice is given it's in the submit interpreter in terms of keeping loop time down etc. Would welcome any thoughts on optimising other sections of the code too (my background definitely isn't in programming...) or if there is a completely different way I should be doing this. Hopefully the code may be of help to others looking to implement serial comms too.

    Edited once, last by cnccreations (June 30, 2024 at 1:52 PM).

  • kwakisaki June 30, 2024 at 9:04 AM

    Approved the thread.

    Using WAIT command in Submit is a bad idea. And leaving it unchecked is as bad as it gets.

    At least add timer limit so it does not get stuck indefinitely

    WAIT FOR ($DATA_SER3 <> 0) or TIMER_LIMIT(1.75) ; wait for data in COM3 buffer but not more than 1.75 seconds

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

    Thankyou panic mode that's a big help.

    I hadn't come across the TIMER_LIMIT function before (but have now found reference to it here on the forum in the hidden functions thread).

    I've added that in and made a few other adjustments, and appears to be working well now. Have gone through several large file copies/moves without any issue. I'll include the updated code below in case it is of use to anyone looking to implement a serial connection.

    Declarations:

    Code
    ;**************Serial Module Declarations*******************
DECL INT CharValue, Handle, Offset, CheckSumCalc, CheckSumRet, SerialFail, I, J, K
DECL CHAR Comma, CheckSum[2], SendString[19], Response[200]
DECL REAL Timeout
DECL STATE_T TX_State, RX_State, CH_State
DECL MODUS_T Modey
;************End Serial Module Declarations*****************

    Initializations:

    Main Code:

    Thanks hermann that's a good point, I could probably wait for $DATA_SER3==197 instead as the response from the PLC should always be the same length and this would avoid any cases where characters are missing, although the checksum should pick this up. My only thought is this may slow the submit loop slightly, as it is waiting until all the data has been received before it starts processing it, although I suspect the difference is negligible.

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