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TI Home » TI E2E Community » Support Forums » Microcontrollers » Stellaris® ARM® Microcontrollers » Stellaris® ARM® LM3S Microcontrollers Forum » RS-232 Communication
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  • RS-232 Communication

    RS-232 Communication

    This question is not answered
    Arjun Namineni
    Posted by Arjun Namineni
    on Aug 08 2012 10:27 AM
    Prodigy30 points

    I am trying to connect to my Stellaris MDL-BDC24 Black Jaguar using CANBus rs-232 communication. I have read documentation on how to encode information and have tried to send it the heartbeat repeatidly; however, the light on the Jaguar doesn't stay solid yellow. I am sending FF 04 40 01 00 00 (heartbeat) every 2-4 milliseconds. What am I doing wrong? Is there a certain interval that the heartbeat must be sending at? I am aware that it times out at 100ms, but I am sending the heartbeat much faster than that.

    Thanks in advance!

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    • cb1_mobile
      Posted by cb1_mobile
      on Aug 08 2012 11:07 AM
      Guru21680 points

      You are aware that your subject line reads, "RS232 Communication," and that your post then steers towards CANBus!  Curious that - no?   These devices require some clarity of thought/mind/execution to succeed...

      Have you tried other - perhaps more elementary commands?  Often a checksum calculation is required - has that been clearly explained and have you so implemented?

      Have not that board - offering general approach till "cavalry" arrives...

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    • Arjun Namineni
      Posted by Arjun Namineni
      on Aug 08 2012 11:35 AM
      Prodigy30 points

      Thank you for that catch. I meant to say that I was communicating with the Jaguar via rs-232. I was confusing myself with the fact that the black Jaguars can convert rs-232 to CANBus.

      I am not entire sure what a checksum calculation is, but I have tried other commands. I sent it FF 04 82 00 02 02, which (according to the interface pdf) sets the voltage that the controller should send the motor. The Jaguar replied with the same response plus 2 bytes of 00 00; probably acknowledging that it isn't sending any voltage through. Although I am getting a response, the light does not hold steady.

      Thanks for your quick response!

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    • cb1_mobile
      Posted by cb1_mobile
      on Aug 08 2012 13:08 PM
      Guru21680 points

      Thank you - that mystery solved.  Now are you absolutely sure that the various RS-232 parameters are all in perfect match, both your Jaguar and RS-232 "remote?"  Usual requirements here are: baud rate, # of stop bits, and communication control bits (hardware flow control)  such as RTS/CTS etc.  Again - you must match your remote to the expectations of the Jaguar - or vice versa.  

      Probably would help if you'd describe your remote RS-232 end (likely a PC) and if you have experience setting the various parameters as described....   Good luck...

      Again - haven't that board - but do know that RDK-BLDC board does accept such commands - and each/every one is, "guardbanded" by a checksum.  You may wish to reread to check - to be on the safe side.

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    • Arjun Namineni
      Posted by Arjun Namineni
      on Aug 09 2012 09:31 AM
      Prodigy30 points

      Yes, I have checked to make sure the baud rate(115.2 kbps), stop bits(1), and others are all the same as what the MDL-BDC24 FAQ specified, so I assume it is what the Jaguar is expecting. I was able to communicate properly with the Jaguar using the same settings from my COM port through the BDC-COMM.

      I am not using a PC to communicate with the Jaguar; instead, I am using a micro-PLC, but it will communicate rs-232 regardless.

      I haven't found any documentation on the checksum (however, I have heard of it). Can you direct me to where I can find more information on how to calculate it?

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    • cb1_mobile
      Posted by cb1_mobile
      on Aug 09 2012 09:52 AM
      Guru21680 points

      So - seems you've done a good job w/RS-232 set-up.  Our group has multiple BLDC-RDK boards - used that as basis to "spin" our extra-featured own board.  W/in the "user guide" - the use and calculation of "checksum" for the BLDC data transfer is detailed.  Again - every command requires the calculation and then inclusion of checksum - in that package.

      Suggest that you search for "checksum" w/in each/every piece of documentation related to your kit.  Checksum calculation may involve "selective" inclusion of start/end bytes - thus you really need the defining detail.  (yet another case of a "standard" (or near one) being subject to different interpretation...)

      Another approach - cannot you, "capture" the serial data sent from your "successful" BDC-COMM implementation?  Once captured - you can compare this data package with the ones you've been attempting - looking for any difference.  It may be necessary for you to monitor beyond just, "printable ASCII" - control codes often come into play in such transmissions...

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