[FAQ] HDC2080/HDC2010 - I am getting incorrect values (for example: -40C or 0%RH or both) from HDC device for my first read (or for any read) – how to troubleshoot the problem?

The programmer should always respect the waiting time for the measurement resolution being used between issuing a “start conversion” command (writing 0x01 to register 0x0F) and reading out 0x04 for 0x80 and then subsequently reading the temperature and humidity registers (0x00 through 0x03). We also recommend the use of the logic analyzer or oscilloscope to see exactly what the microcontroller firmware is doing and how the HDC device is responding for being able to quickly troubleshoot I2C or timing issues.

Here below are examples using modified MCU code to induce two faults and then produce success based on conversion waiting time specification for the HDC20x0 devices, in this case with the part set for doing 14 bit resolution measurements for both temperature and humidity, which together should typically take around 1270uSec.  

Example 1: 250uSec waiting time on 14bit conversion results in a failure of both new temp and %RH data with all zeros are being returned, as the part clears these registers before starting the conversion. This would result in calculated temp and humidity returns of -40°C and 0%RH, respectively.

Example 2: 500uSec waiting time on 14bit conversion results in a failure of new %RH data only, as temp conversion was completed, and values loaded, but not enough time has been allotted for the humidity measurement to complete and be loaded. This would result in calculated temp value being correct and still have a humidity return of 0%RH.

Example 3: 1300uSec waiting time on 14bit conversion for both measurements together results in success, as the correct amount of time was allotted for the conversion to complete and be loaded into the registers.