I2C communication with Honeywell HumidIcon RH sensor problem

[yinni]

Hello,

I used Sensirion SHT35 for humidity and temperature measurement and the I2C communication between my Kinetis K50 100MHz 100LQFP and the sensor has been working fine. Now we switched to Honeywell Humidlcon RH sensor. When I sent out the measurement request command (which is very simple, just the 7-bit sensor address, 0x27 by default, followed by a '0' as write), the sensor never returned ACK.

I first check the hardware connection, which is strictly conformed with the sensor datasheet, measured the power supply voltage, which is 3.3V as expected, and reduced the SCL frequency to be lower than 100kHz, still no ACK from the sensor.

I suspected the sensor was damaged during soldering, and replaced it with a new one, the same result. I am on my wits' end, any suggestion would be appreciated.

Please find the attached for the waveform from logic analyzer and part of the code.

[mjbcswitzerland]

Hi

Address 0x27:

Try sending 0x5e for a write and 0x5f for a read (maybe the I2C address is referenced shifted in one case and non-shifted in another which can lead to confusion).

If you have no luck, put the read/write call that is not being acked in a loop which sends to all 128 possible addresses) and see which one an ACK is received on.

Regards

Mark