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HDC1010: I2C issue

Longchang Chen
Intellectual 1350 points
Part Number: HDC1010

We encountered another question, we found that when the sensor was read it always give NOT ACK until 72 cycles (about 7ms) try and success in the last read, not sure it is normal, we noticed in the datasheet there will be NOT ACK when it is in transition(3.6ms), but we are not sure where it start and stop for the 3.6ms, could you help to explain?

In our application, I2C will try long time(1.34s, hex 2000000*40ns) to read when no ACK. Will such long try has any negative effect?

Pls also find the capture as below.

  • 0
    TI__Guru* 91206 points

    Dear Longchang -

    I can see Looks like you don’t let go of the line so the part can ACK the setup to read?

    See image I marked up below.

    vs similar write then read transaction with ACK being allowed to occur on setup to read 

     

    Can you check that? Which MCU are you using? Is this bit bang or using I2C engine?

    -------------added 5min later---------------:)

    also - i just realized the part is probably telling you the data is not ready because that is NACK by the slave

    See figure 13 on page 13, here ==> http://www.ti.com/lit/ds/symlink/hdc1010.pdf

    If you use the DRDY pin to trigger the read, this would probably be best - this is described in step 3 of section 8.5.2.3 of the datasheet, too - page 11. 

    Basically, i would recommend you use the DRDY pin or at most wait the conversion time (or perhaps more) - if you are wanting to 'blindly' poll the register - 

    times to wait are: 

    2.50mSec to 6.50mSec, based on your resolution setting. 

    thanks