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That means that the I2C bus does no longer work according to the I2C specifications. There are however some Wire compatible libraries that already put a START condition on the I2C bus. The Wire.beginTransmission() clears a few variables to get ready to write to a sensor. Wire.beginTransmission(0圆8) <- common mistake, don't do this It works together with Wire.endTransmission() but not with Wire.requestFrom(). The Wire.beginTransmission() should only be used when writing data. Mistake 3: Using Wire.beginTransmission() before a Wire.requestFrom() Since there are a number of Wire compatible libraries, other libraries can do other things. The Wire.endTransmission() could start an extra I2C bus transaction and then the sensor acknowledges to its address. Wire.endTransmission() <- common mistake, don't do this

It should only be used when writing data and only together with Wire.beginTransmission(). The Wire.endTransmission() has no part in this. The Wire.requestFrom() will do a complete I2C bus transaction with: START, send address, read data, STOP. Mistake 2: Using Wire.endTransmission() after a Wire.requestFrom() If such a problem is detected, the Wire.available() might also return zero, and that while(Wire.available() < 2) code will stop the sketch. The Wire library can detect a few problems on the I2C bus. That while(Wire.available() < 2) code will run forever and the sketch will stop. When the sensor is not connected, the Wire.available() will return zero.

Sometimes the waiting is done with a delay or with using millis(): Wire.requestFrom(0x28, 2) ĭelay(10) <- common mistake, don't do this While(Wire.available() < 2) <- common mistake, don't do this Sometimes the waiting is done with a while loop: Wire.requestFrom(0x28, 2) If data was received, that data is in a buffer (inside the Wire library) and ready to be read with Wire.read().

That means that no waiting after the Wire.requestFrom() has been called is needed. It will wait until the I2C bus transaction has finished. Mistake 1: Waiting after calling the Wire.requestFrom()