Uploaded image for project: 'Embedded Software & Tools'
  1. Embedded Software & Tools
  2. EXT_EP-9789

ADCBuf causes jitter when switching clock sources

    XMLWordPrintable

Details

    • Bug
    • Status: Accepted
    • Medium
    • Resolution: Unresolved
    • TI Device Drivers
    • TIDRIVERS-4127
    • TIDRIVERS_5_10_00
    • TIDRIVERS_5_20_00
    • Hide
      CC13x2
      CC26x2
      Show
      CC13x2 CC26x2
    • Hide
      Two Workarounds
      1. Use asynchronous sampling mode at the cost of a slightly corrupted sample because the sampling timing is slightly shifted
      2. Ensure that no clock switches take place while using the ADCBuf (always run on XOSC_HF while ADCBuf active)
      Show
      Two Workarounds 1. Use asynchronous sampling mode at the cost of a slightly corrupted sample because the sampling timing is slightly shifted 2. Ensure that no clock switches take place while using the ADCBuf (always run on XOSC_HF while ADCBuf active)

    Description

      At the maximum sampling rate of 200 kHz, CC26X2 devices have 120 clock cycles at 120 MHz to perform the ADC conversion. The hardware requires 118 clock cycles to perform the ADC conversion. Clock switching from XOSC_HF to RCOSC_HF, and vice-versa, consumes two clock periods.

      During clock source switching, using the TI Power driver, the ADC will run off a different clock source than the timer that generates the ADC triggers for a while. This is a problem, because the clock switch itself uses the whole time margin, so there is no margin left for any rate differences between the XOSC and the RCOSC. The next trigger as a result may be generated while a conversion is ongoing and thus do nothing.

      Attachments

        Activity

          People

            syncuser TI User
            syncuser TI User
            Votes:
            0 Vote for this issue
            Watchers:
            2 Start watching this issue

            Dates

              Created:
              Updated: