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HDC2022: HDC2022 One-shot mode can't read back data

andy wang2
Prodigy 90 points
Part Number: HDC2022
Other Parts Discussed in Thread: TMP116

Hello everybody,

we are developing HDC2022 with one-shot acquisition mode, but per some tested, we found sometimes i2c SDA waveform can not down to zero while it is low, that will cause of ready back data is error. do you have met similar case?

Thnaks your help.

Andy

  • 0
    TI__Guru* 91206 points

    Dear Andy - 

    Thanks for posting! Your attached image is not very clear, it is very hard to see it. If possible, please make it larger or retake the scope shot, so we can see what exactly is the issue. If you have a schematic to share, that would also be helpful. 

  • 0 in reply to Josh Wyatt
    Prodigy 90 points

    Hi Josh,

    Thanks for your reply, I attached clear picture for what we found problem, you can see the HDC2022 SDA pin's signal is abnormal, that is why we can't ready back correct value.

    We used is HDC2022 one-shot mode and I2C 400khz for temperature and humidity measurement, i also attached our schematic capture here.

    Only one thing should suspicious is we share use same one SOC I2C SDA&SCL to driver HDC2022 and TMP116, any chance generate interference like this? but even we disconnection I2C with TMP166 , only keep the connection for HDC2022, but the abnomal still exist.

    Andy

  • 0 in reply to andy wang2
    Prodigy 90 points

    Hi Josh,

    I would like replenish normal and NG SDA signal compare picture to you as below.

    Andy

    Normal:

    NG:

  • 0 in reply to andy wang2
    TI__Guru* 91206 points

    Dear Andy - the small spikes are ACKs. If you were able to capture two channels at one time and add the SCL channel, then you would see the relationship. Its pretty normal looking, but the edges of your SDA signal you show there could be sharpened up a little bit, have you measured the line capacitance or tried lowering the pullup resistors?