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RTOS/CC2652R: CC2652R sensor controller could not work if VDDS voltage below 2.8V but above 2.2V

behold li
Expert 2745 points
Part Number: CC2652R
Other Parts Discussed in Thread: BOOSTXL-ULPSENSE

Tool/software: TI-RTOS

The main MCU work well,but internal capacitive sensor controller could not work if voltage below 2.8V,if VDDS voltage above 3V,all feature work well.

I found the CC2652R datasheet,Supply Voltage Range: 1.8 V to 3.8 V

  • 0
    TI__Genius 9215 points
    Hi,

    Can you please elaborate a bit on what you mean by Sensor Controller do not work below 2.8V?
    Is it that the Sensor Controller stops responding or that the implementation of capacitive sensor application stops working properly?

    Best Regards,
    R.M
  • 0 in reply to R.M
    Expert 2745 points
    Our main power is CR2032 cell battery,if voltage below 2.8V,CC2652R could rejoin zigbee network successful power up again,but capacitive touch could not work,if voltage above 3V or 3.3V with new cell battery,cap touch work well.

    Our design reference CC2652R Launchpad+BOOSTXL-ULPSENSE reference design.
  • 0 in reply to behold li
    TI__Genius 9215 points
    Hi,

    Can you share your Sensor Controller project?
    If you don't want to share it here on a public forum please send me a friend request.

    Best Regards,
    R.M
  • 0 in reply to R.M
    Expert 2745 points

    attachments is SCS project and for RTOS capacitive touch project archive.

    cap_touch_ulpsense.zipCC2652R capacitive RTOS.zip

  • 0 in reply to behold li
    TI__Genius 11810 points
    Hello Behold,

    The Cap. Touch example in Sensor Controller Studio does not take account for bigger voltage variations, so you have to do some modifications to the example to be more robust over voltage. I have tested your code and it seem to work for slowly decreasing voltage, but not fast nor voltage increase since the baseline value is updated slowly. However, if I restart the code it seem to work on every voltage level. I suggest that you add some smart filtering or logic to you code to compensate for voltage variations. Finally, be aware that you need to tune the comparator reference (Rbias) if you require operation below 2.4 V.

    -Simon
  • 0 in reply to Simon J
    Expert 2745 points
    Hi Simon,
    I will tune the Rbias and test continue.
  • 0 in reply to behold li
    TI__Genius 11810 points
    Hi,

    Ok, just be aware that the current source is limited to 20 uA maximum.

    -Simon
  • 0 in reply to Simon J
    Expert 2745 points
    In other words,increase the Rbias ?
  • 0 in reply to behold li
    TI__Genius 11810 points
    Yes.

    Alternatively, you can use the internal DAC as reference instead of Rbias.

    -Simon
  • 0 in reply to Simon J
    Expert 2745 points

    is it needed select cap touch external reference resister if use the internal DAC as reference? How to select options in Sensor Controller Studio?

  • 0 in reply to behold li
    TI__Genius 11810 points

    With the DAC you don't need an external resistor. We have just started to play with this solution, so we don't have the same experience as with the Rbias solution.

    I have attached the Sensor Controller Studio project, so you can start playing with it and test if if works better for your application.

    -Simon

    https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/158/cap_5F00_touch_5F00_ulpsense_5F00_dac.scp

  • 0 in reply to Simon J
    Expert 2745 points

    Hi Simon,

    The DAC example without external Rbias (1.2 Mohm) is work well in CC2652R Revision C platform,I have configure four cap touch buttons,but there are have a problem,

    1. CC2652R power consumption approximate is 12.8uA(19 uA sometimes) with four cap touch buttons,is it possible further reduce power consumption? Our expected power consumption is less than 5uA

    by the way,how to modify sensor project to suitable bigger voltage variations?

    Attachment is our Sensor project file:

    https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/158/cap_5F00_touch_5F00_ulpsense_5F00_dac_5F00_for_5F00_CC2652R_5F00_RevisionC.7z

  • 0 in reply to behold li
    TI__Genius 11810 points
    Hi Behold,

    I have not yet measured the current consumption of using the DAC as reference voltage, but I'll expect this solution to use more current than using Rbias.

    You can use BATMON to read the VDDS voltage (search for BATMON in the Sensor Controller Studio Help Viewer (press F1) to find code example) and use this voltage to adjust your cap. touch parameters (threshold, DAC output voltage etc.)

    Best regards,
    Simon
  • 0 in reply to Simon J
    Expert 2745 points
    I have do test again,Rbias solution power consumption is same as Rbias(12uA),how to reduce power consumption?
  • 0 in reply to Simon J
    Expert 2745 points

    Hi Simon,

    As previous mentioned,is it possible further reduce power consumption if cap touch sensor enabled?

    I have been solved cap sensor could not work encounter voltage variation whenever power up CC2652R with CR2032 battery solution,only change Sensor Controller Studio CC2652R project "Initialization Code" as following.

    // Clamp all capactive touch pins to ground
for (U16 n = 0; n < PIN_COUNT; n++) {
    isrcClamp(cfg.pAuxioAxdCapTouch[n]);
}

// Schedule the first execution
//delay ~200ms to start event handler
evhSetupTimer1Trigger(0, 200, 2);

  • 0 in reply to behold li
    TI__Genius 11810 points
    Hi,

    You may be able to reduce power consumption if your application can allow slower samping of the buttons. The default sampling frequency is 32 Hz while touch is not detected, and ~100 Hz while touch is detected. You may be able to reduce those parameters at the cost of slower reaction to touch.

    -Simon
  • 0 in reply to Simon J
    Expert 2745 points
    I have been tested,change D_MAX_SMPL_PERIOD from default 128 to 512,the CC2652R deep sleep power consumption reduce to 3.9uA~5.1uA,it's very good,cap touch was work well,I have do test again,change D_MAX_SMPL_PERIOD to 1024,cap touch was work well too, and power consumption reduce to dynamic change in range of 1.2uA~ 3.9uA,I don't know it is seems not stable.
  • 0 in reply to behold li
    TI__Genius 11810 points
    Good that you are able to save power and also achieving the performance you are expecting!

    You may also fine tune the ISRC current. See the cap. touch SLA for more detailed information: dev.ti.com/.../

    -Simon
  • 0 in reply to Simon J
    Expert 2745 points
    Hi Simon,

    How to prevent cap touch button overlay long time unexpected in sensor?
  • 0 in reply to behold li
    TI__Genius 11810 points
    Hi Behold,

    Apologies for my late reply - I have been out of office for a while.

    I'm not sure if I understood your last question, can you please rephrase?

    Thanks,
    Simon
  • 0 in reply to Simon J
    Expert 2745 points

    As you know,is there have plan to release DAC solution for cap. touch?

    I have been resolve the issue that cap. touch overlay unexpected the touch triggered always,only comment one line sensor source code,

            // Find whether we should generate any output
        if (touchDetNow != state.pTouchDet[n]) {
            state.pTouchDet[n] = touchDetNow;
            state.genOutput = 1;
        } else {
            //state.genOutput |= touchDetNow;
        }

  • 0 in reply to behold li
    TI__Genius 11810 points
    Hi,

    We don't have a timeline for the DAC solution yet.

    -Simon