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HDC3022-Q1: Consultation on technical issues of humidity sensors

ian wu
Intellectual 775 points
Part Number: HDC3022-Q1
Other Parts Discussed in Thread: HDC3020

Tool/software:

hi Expert

Regarding HDC3022QDEJRQ1, our company has the following questions to consult. Please help confirm:

1.How to switch between the fast mode and the fast + mode of the humidity sensor? Can the fast + mode be used by default

2.Can the ALERT pin be set to a logic high level only for the threshold alarm of humidity? Does the RESET pin described in the specification sheet keep this pin low so that power-on and any reset events cannot activate the ALERT output logic high level?

3. How long is the fastest time for IIC communication to read the status register once?

  • 0
    TI__Genius 12185 points

    Hi Ian,

    Fast mode + can be used by default. There is no need to enter regular fast mode and then switch. Yes the ALERT pin can be activated only for humidity events. The nRESET pin does not keep the ALERT low. The nRESET pin when pulled low will just clear the ALERT condition.

    The HDC3020 supports I2C speeds up to 1MHz, meaning 1us per clock cycle. Since you will need to perform the following sequence to read from the status register:

    There are about 66 bits in this sequence. Not accounting for any delay time between these bytes, it would take at a minimum of 66us to read the status register.

    Regards

    -Alex Thompson

  • 0 in reply to Alex Thompson
    Intellectual 775 points

    1.Can the ALERT pin of the humidity sensor only raise the alarm when the humidity threshold is high, without raising the alarm when the humidity threshold is low or in other situations

    2.What consequences will there be if other commands or communications occur within 77 milliseconds after the write and read operations on NVM are completed? Will other commands that appear fail?

    3. Does the 61BB read command for NVM have to be in sleep mode to read the default Settings? If it enters the automatic measurement mode immediately upon power-on, can the NVM be read normally

  • 0 in reply to ian wu
    TI__Genius 12185 points

    Ian,

    1. The ALERT pin will raise alarm in both high humidity threshold and low humidity threshold. I don't think you can outright disable the humidity low ALERT flagging, but you can set the ALERT limits to be very low, lower than the defaults, to make it very unlikely the ALERT flags for low RH.

    2. Do not, under any circumstances, communicate with the HDC3020 during the 77ms NVM operation. Doing so will corrupt the NVM registers, which will lead to compromised device capabilities and performance. This is not something a user can recover, so you cannot have any communications occur during the  77ms window.

    3. Whenever you engage with the NVM, reads or writes, place the HDC3x into shutdown mode first. I'm not sure if NVM corruption can occur with just reading when a unwanted conversion occurs, but I would not risk it.

    Thanks

    -Alex Thompson

  • 0 in reply to Alex Thompson
    Intellectual 775 points

    We need to configure the humidity sensor in the NVM to enter the automatic measurement mode by default upon power-on, and we also need to read the NVM once after each power-on to verify whether the configuration command is the one we set before. Currently, I can successfully read the NVM configuration after powering on and entering the automatic measurement mode. However, your reply is that there is a significant risk in reading the NVM when it is not in sleep mode. Therefore, I would like to ask if there is a better way.

    Also, I would like to ask, after the humidity sensor is configured in NVM to automatically measure and detect humidity alarm upon power-on by default, if the sensor breaks down at some point, is there any way in software or hardware to detect whether the sensor is still working normally?

  • 0 in reply to ian wu
    TI__Expert 4840 points

    Hello Ian,


    Alex will be back tomorrow and can comment on reading the NVM.

    As for your second question. It's a little difficult to answer since degredation behavior is hard to predict for any device due to many uncontrollable factors. Some ways you could verify the sensor's performance is if its output was compared to a calibrated probe. However, in the case a device malfunctions completely, the MCU could be notified if the I2C bus fails to retreive an ACK from the sensor.

    Regards,

    Harry

  • 0 in reply to HarryG
    Intellectual 775 points

    hi  

    dould you  comment on reading the NVM.

  • 0 in reply to ian wu
    TI__Genius 12185 points

    Hi Ian,

    Thanks for your patience. I was checking on your questions from our design team, and readings from the NVM should be OK after power-on even when the HDC3x is starting up in automatic measurement mode. This is because on power-up, the NVM is read and copied into registers. So when you check to make sure the NVM is what you want it to be to verify automatic measurements will be done on power up, you are reading from these registers and not the NVM (which makes the transaction safe). You can begin these reads after the sensor ready time. 

    Thanks

    -Alex Thompson