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Original question:

Draw graph in realtime CCS

CCS/TMS320F28335: What is the REAL sampling time of a debuging graph?

Leonardo Abbate
Prodigy 90 points
Part Number: TMS320F28335

Tool/software: Code Composer Studio

So I´ve been reading many posts about this subject and also the CCS user´s guide but I can´t find any definitive answer to this question.

I´ve read the following so far:

  • I must create in my program a buffer array that stores the data to be graphed so that CCS can retrieve them all once in a while (how often CCS does this is the question).
  • On graph properties the sampling rate is only used to make the conversion from samples to time scale. It actually has no effect on the real sampling rate of the graph (I can input 999999999999999999 and CCS won´t ever say that is too high. This seems to be confirmed by the user´s guide "The sampling rate is used to calculate the time and frequency values displayed on the graph".
  • On preferences>code composer studio>debug the "continuous refresh interval" only determines the refresh rate of the graph.

So my question is: What is the sampling rate of CCS?

I need to know this to know how long the buffer must be to avoid missing datapoints. I would just read this value with an oscilloscope if I could but my microcontroller has no DAC and all PWM pins are already used on other stuff so the PWM conversion trick can´t be used.

  • 0
    TI__Guru**** 169094 points

    Hi,

    Leonardo Abbate said:
    I must create in my program a buffer array that stores the data to be graphed so that CCS can retrieve them all once in a while (how often CCS does this is the question).

    You can either use an array or plot each sample one by one. However, the maximum data rate is limited by SW to 0,1s but this only happens under ideal conditions (fast Debug Probe, lightweight PC load, etc.)

    Additional information can be found at: e2e.ti.com/.../1112620 ?

    In addition to that, you can always try to do some post processing on the memory data by saving its contents and plotting/analyzing with an external software. Details can be found at:

    software-dl.ti.com/.../ccs_debug-main.html

    Hope this helps,

    Rafael