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LAUNCHXL-F28027F: SCI stops when system gets enabled

Michael Mätzler
Intellectual 320 points

Part Number: LAUNCHXL-F28027F
Other Parts Discussed in Thread: DRV8305

Hi,

I tired to add a SCI communication to my LaunchXL F28027F and DRV8305.

Everything works till Flag_enableSys gets set. From there on the communication fails and just a few single values are received from time to time. 

The SCI is set up like described in the Hal tutorial but for me it seems that there is something wrong with the priority..

Anyone expired the same problem or got a solution for this?

Many thanks in advance.

Br,

  • 0
    TI__Guru** 117000 points
    Are you using the SCI TX&RX interrupt for communication, or using the query mode in background loop? And what PWM frequency are you using? How many CPU bandwidths can be reserved for SCI communication code? Are there any signals on TX or RX pins? Did the issue on TX and RX, or only one? Some signal waveform could help to find the cause of this question.
  • 0 in reply to Yanming Luo
    Intellectual 320 points

    Thanks for you fast response.

    I am using interrupts for communication. The pwm frequency is 45kHz. Have not measured the cycle time yet but since there is just lab 4 running and every 100 milliseconds four byte at the SCI i would assumed it`s just fine.

    Also made some pictures.  

    For the communication:

    -Another µC sends every 100ms four byte (Start byte,  two byte data and a checksum) (yellow curve, Rx of F28027F, GPIO28)

    -F28027F receives them via interrupt and answers also with 4 byte (start byte, two (different) bytes data and a checksum) (red curve, Tx of F28027F, GPIO29)

    They look exactly the same either the flag is set or not. But if it is set the F28027F answers back sporadic every 5s or so. (The Rx signal looks fine all the time).

    As soon as Flag_enableSys get set the communication fails. 

  • 0 in reply to Michael Mätzler
    TI__Guru** 117000 points
    What's the SCI baud rate? You might try a lower baud rate like 600bps first.
  • 0 in reply to Yanming Luo
    TI__Guru** 117000 points
    Hi Sir,

    It's been two weeks since we heard from you, so I am assuming you no longer need clarification for your question that will be marking this thread as closed. You can reply with a post or create a new thread if you have any further question on this topic. Thanks.
  • 0 in reply to Yanming Luo
    Intellectual 320 points

    Have tried it but still got the same problem.

  • 0 in reply to Michael Mätzler
    TI__Guru** 117000 points
    You might try to increase the wait time between each sent or received byte. And you can add a test variable to check if the receiving data is missed.
    And you should have a check on how many cpu cycles will be taken by these two interrupts (motor control and SCI). The root cause is the timing assignment for the control states in your project, is not from the configuration of SCI.
  • 0 in reply to Yanming Luo
    TI__Guru** 117000 points
    Hi Sir,

    It's been a week since we heard from you, so I am assuming you no longer need clarification for your question that will be marking this thread as closed. You can reply with a post or create a new thread if you have any further question on this topic. Thanks.