Android Things I2C驱动程序PioException：I / O错误

Question

Hello dear pioneers of Android things!

I am calling for your help as I have been triying for the last couple of months to build an android things driver for the Adafruit SI7021 Themperature and humidity sensor. Here is the link to the github repository hosting the project. Connecting and Getting the chip id with readRegByte work fine. But, I get a PioException: I/O error while trying to retrieve Temperature or humidity data using readRegBuffer .

int address = 0xE5; // from datasheet
byte[] buffer = new byte[3];

device.readRegBuffer(address, buffer, 3); // throws PioException

I don't know what other clue I can give you to get a clear idea of the problem so do not hesitate to ask any question.

Please don't make me buy an arduino and start all over again ;)

Thank you so mutch!

PS: Use simple words I am a beginner in IoT and Android.

Answer 1

The readRegBuffer does not do what I believe you expect. From [the API documentation]( https://developer.android.com/things/reference/com/google/android/things/pio/I2cDevice.html#readRegBuffer(int , byte[], int)):

Read multiple bytes from a given register.

This method would be used if the register you wanted to read was 3 bytes long (24 bits). Looking at the part's datasheet (p21), register 0xE5 for relative humidity appears to be a 2-bit word.

Expecting 3 bytes will create a problem as your device will be expecting 3 bytes to be returned. However, if only two bytes come back there will be an inconsistency in the actual result.