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MSP430FR2676: CapTIvate scan period

Koichiro Tashiro
Mastermind 21150 points
Part Number: MSP430FR2676

Hi,

I have questions from my customer for CapTIvate.
Customer understood scan period can be configured by.ui16ActiveModeScanPeriod parameter.
But it seems the minimum value is 1msec.

Q1)
Suppose CapTIvate is configured as below,
Mutual, 1 TX, 8 RX
Conversion Count=500
Frequency divider=1
No oversampling
Scan Time Estimation in CapTIvate Design Center GUI shows below.
Sensors Total is only 0.165msec.

Customer wonders if he can minimize Scan Period less than 1msec.

Q2)
CapTIvate GUI can output the scan data to CSV file.
Customer got the CSV data with above configuration.
.ui16ActiveModeScanPeriod is set to 1msec.
With this configuration, scan rate should be 1msec, but the CSV data shows only 835 scans in 3016msec, i.e 3.6msec average scan rate.
Does the CSV file include all scan data?
Or some data are decimated by some reasons?

Thanks and regards,
Koichiro Tashiro

  • 0
    TI__Mastermind 32920 points

    Q1: Yes you can.

    Q2: What about your application code? I would suggest you use GPIO to show the real time of the CAPT_appHandler() and its frequency.

    Actually, this time calculation is not so right, especially you use oversampling mode.

  • 0 in reply to Eason Zhou
    TI__Mastermind 21150 points

    Hi Eason,

    Thanks for your quick reply.

    Q1: Could you tell me how to do that? GUI cannot accept less than 1msec.
    Customer needs to change .ui16ActiveModeScanPeriod in software?
    If so, .setting ui16ActiveModeScanPeriod = 0.2 makes scan period = 0.200msec, for example?

    Q2: Customer disables oversampling.

    Eason Zhou said:
    Actually, this time calculation is not so right, especially you use oversampling mode.

    Do you mean the GUI scan period is not so right and the CSV data output is correct?

    Thanks and regards,
    Koichiro Tashiro

     

  • 0 in reply to Koichiro Tashiro
    TI__Mastermind 32920 points

    Q1: Sorry, I didn't explain clearly.  Here is the setting of the timer frequency.

    As the clock source is ACLK(32.768kHz). Here is the definition of MS_TO_CYCLES. That means if customer input 1, the frequency would be 1/32.768 ms.

    Q2: I mean, customer need to test this by themselves. There are two possibility to cause this problem:

    1.  This Time calculation by GUI is not so right

    2. The time calculation doesn't include customer's added code.

  • 0 in reply to Eason Zhou
    TI__Mastermind 21150 points

    Hi Eason,

    I see. The customer put GPIO toggle code and measured the interval.
    He confirmed the cycle period is the same as the value configured in .ui16ActiveModeScanPeriod if the interval is 1msec or longer.
    Then he manually changed the argument for MAP_CAPT_writeTimerCompRegister() and measured the interval.
    Even MAP_CAPT_writeTimerCompRegister(1), means 1/32 [msec] = 31.25 [usec] configuration, the interval is 0.96msec.
    It seems this is the minimum interval.

    The code customer uses is the simplest GUI generated code and no other functions are added.
    Data output is disabled.
    .bElementDataTxEnable = false,
    .bSensorDataTxEnable = false,

    Is this 0.96ms the minimum possible interval?
    Any potential configurations to reduce the scan period?

    Thanks and regards,
    Koichiro Tashiro

  • 0 in reply to Koichiro Tashiro
    TI__Mastermind 32920 points

    1. The lowest time is determined by this function. I would suggest customer to test this directly.

    2. Customer can decrease the scanning time by change these parameters. Hope this can give help.

  • 0 in reply to Eason Zhou
    TI__Mastermind 21150 points

    Hi Eason,

    Sorry for the delay.

    Eason Zhou said:
    1. The lowest time is determined by this function. I would suggest customer to test this directly.

    Could you explain a bit more about that function?
    The customer found the code, but it is not clear what exactly he should test.
    Do we have document for the function?

    Thanks and regards,
    Koichiro Tashiro

  • 0 in reply to Koichiro Tashiro
    TI__Mastermind 32920 points

    I mean that customer can use GPIO toggle before and after MAP_CAPT_updateUI() function. The  time means the time used for key scan and data handling.

    All things to do is to short the time used by MAP_CAPT_updateUI(). For the method you can refer to the second point in my last post.

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