HDC3020: HDC3020 function issue

Dear Rock - 

Thanks for the post, the schematic you sent over looks to be wired correctly for 0x44(7bit) I2C address. 

Here we can help you with technical issue - if you want to post up your logic analyzer shots of your communication, that would be helpful.

Returns are handled in this manner ==> https://www.ti.com/support-quality/additional-information/customer-returns.html 

Please visit this page, scroll down slightly and see the Situation/Action table recommended there. 

Dear Rock, thanks for the captures. 

On fail 1 image, it appears you are not waiting long enough between issuing "trigger on demand" and attempting a read. I was able to duplicate your issue by reducing the wait time down to ~7.5mSec and got back exactly same results as you. Anything above that I was able to get both sets of values. 

On the other two, they both look like possible soldering issues, one for address line, as the device NAKs the address you intended and the other one, the SCL line pullup is low, which means you are missing a pullup (could be soldering) or another device on the bus is clock stretching.