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MSP430FR2633: Lower Lta

rei
Mastermind 6155 points
Part Number: MSP430FR2633

Hi

My customers use a custom board with the MSP430FR2633 and a capacitive touch sensor(CapTIvate).
They are plagued by the problem of proximity sensor false detection.
Looking at "ChannelOscilloscopePlot" in the design center, they found the following.

Normally, the values of Count and Lta (Channel Data) are almost the same.
When abnormal, the value of Count is lower than Lta, and detection continues.

Question 1:
Would you tell me why Count and Lta do not have the same value.

Question 2:
We are considering recalibration using SensorTimeoutThreshold as a measure to lower Lta.
Is it correct usage?

Regards,
Rei

  • 0
    TI__Genius 9570 points

    Hi rei,

    Q1: Normally, the values of Count and Lta (Channel Data) are almost the same. Count is measure results, the refresh rate is 33 times per second. LTA is long time average.

    Q2; Yes, it is correct.

    But it is better to find out what cause the abnormal detection.

    Would you please provide your sensor configuration such as conversion count and conversion gain?

    Ling

  • 0 in reply to Ling Zhu2
    Mastermind 6155 points

    Hi.
    Thank you for your reply.
    First, use SensorTimeout.

    I think that it is necessary to identify the cause.
    I got a config file from the customer, so I uploaded it.
    captivate_config.zip

    The problem is happening with proximity sensors.
    There are two patterns for the Count value to become abnormal.

    ・ Move away and move closer(repeat)
    ・Leave the proximity sensor for 20 to 30 minutes

    Question :
    Would you tell me the effective parameter to solve this problem.

    Regards,
    Rei

  • 0 in reply to rei
    TI__Genius 9570 points

    Hi Rei,

    The config file shows that customer set proximity conversion count to 2000 and prox threshold 26 which makes proximity sensor very sensitivity.

    We don't recommend to set conversion count too much above 1000.

    A few thing customer can try:

    Set conversion count to 1000.

    Set timeout threshold to 100, which means if proximity sensor is triggered last 33ms*100= 3.3s, proximity sensor will be recalibrated.

    Ling

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