MCP9808 Temperature Reading Incorrect

[MakerMan]

Hello

I am having problems getting the correct temperature from a MCP9808

I am using the Arduino IDE and have tried both the MCP9808_RT and the Adafruit MCP9808 Libraries

In all cases, the temperature returned is -34 degC while the board is at room temperature.

Having failed to get this working, I tested this with the mcp9808_test and this still returns the same temperature. This reports that the manufacturer is '84'.

I know that the I2C connection works since other devices on the bus are working fine (I also tested this with only the '9808).
I have tested this with two different ESP32s

If I heat up the sensor, the temperature reading increases.

The 9808 is powered from the +3.3V pin of the ESP32 which is powered via USB. I looked that the power rail on a scope and it is clean at 2.27V measured. A small capacitor across the power rails did not make any difference.

I don't have another 9808 to test with. I have checked the soldering on the board and that looks fine.

So I'm a bit stuck with this and any suggestions would be welcome!

MM

[MakerMan]

For testing, I bought another couple of these and they both worked out of the box.

Same manufacturer chip ID reported in testing. The new ones I got have a different PCB layout.

I'm guessing that quite simply the first board I got was faulty.