HDC1080: HDC1080

peter

Part Number: HDC1080

Hello,

I am trying to use the I2C bus to read temperature and humidity from the HDC1080. I am able to access all the registers such as manufacturer ID and device ID but I always get a nack when I try to read temperature or humidity.

I think I am following the exact procedure described in the manual and also mentioned in some posts on this forum. I setup the configuration register, write a zero to the pointer register to trigger the conversion and then wait at least 6.8ms but I always get a nack when I read the temperature (0x00) or humidity (0x01) registers. I have tried waiting up to 1.5 seconds but always get the nack.

The documentation is a little loose on triggering the conversion. It is my understanding that I should send a two byte message on I2C to the HDC1080 to trigger. The first byte is the device address with write indicated. The second byte is a value of 0x00.

Can anyone think of a reason that I always get a nack when accessing the temperature or humidity registers.

Thanks,

over 2 years ago

0 Eddie LaCost over 2 years ago

TI__Mastermind 43580 points

Hello Peter,

Do you have logic analyzer captures of your communication?

Also, take a look at the attached PDF regarding the communication flow. When you send the start conversion, be sure you are sending a stop as well. That was a problem I have seen previously. There are also some more details in the thread below.

file:///C:/Users/a0220986/Downloads/HDC1080_Software%20Flow.pdf

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/920218/hdc1080-temp-and-humidity-data-become-0xffh-rarely

0 peter over 2 years ago in reply to Eddie LaCost

Prodigy 40 points

Thanks for helping. Here are some scope plots of my temperature read. I trigger on the write and read of the configuration register, value 0x1000. Then at 7ms I send the trigger and at 20 ms I try to read the temperature register, but get a nack.

This is the trigger command.

This is the temperature read with the nack shown.

Please tell me where I am going wrong.

Thanks,

0 peter over 2 years ago in reply to peter

Prodigy 40 points

OK, I see my problem. Before I do the read from the temperature register I am sending the pointer again. That re-triggers the conversion so that the following read nack's because the conversion is not complete. Anyway, thanks for the help.

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HDC1080: HDC1080