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HDC1080: When the temperature and humidity are ongoing measurement., can the values of the temperature and humidity output registers be read?

Qianfeng Tang
Prodigy 10 points
Part Number: HDC1080

It is written on page 12 of the datasheet：

It is possible to read the output registers (addresses 0x00 and 0x01) during a Temperature or Relative Humidity
measurement without affecting any ongoing measurement. Note that a write to address 0x00 or 0x01 while a
measurement is ongoing will abort the ongoing measurement.

 

But during testing, I was unable to achieve it. When HDC1080 is performing a measurement and the command to read the current address is issued, the write address (read operation) will return NACK.

So, how should this section in the datasheet be interpreted?

  • 0
    TI__Genius 11865 points

    Qianfeng,

    Did you try to read the temp/humidity results in registers 0x00 and 0x01 which the datasheet says you can, or were you trying a different communication?

    I personally find this section of the datasheet confusing and a little contradictory, since it says reading is OK from these registers during a conversion, but writing is bad (but these are registers we would only read from anyway). So to be safe, I just wouldn't communicate while the HDC1080 is actively converting.

    Thanks

    -Alex Thompson

  • 0 in reply to Alex Thompson
    Prodigy 10 points

    Yes, after triggering the conversion, if we wait for 20ms, we can read the temperature and humidity by reading the current address. However, if a measurement is in progress and an I2C send address + read operation is attempted, it will return NACK. This means that when a measurement is in progress, the last completed but unread result cannot be retrieved.

  • 0 in reply to Qianfeng Tang
    TI__Genius 11865 points

    Qianfeng,

    Yes that is normal behavior I would expect from any of our humidity sensors. I think the best way forward is just to not communicate during an active conversion, so that you can read data reliably. I think the datasheet sentence saying that you are able to is misleading, since I would never recommend communicating during an active conversion.

    Thanks

    -Alex Thompson