Usage of Arduino Wire library

In many files where Wire.requestFrom() is used, I see the comment: "/ blocking call - at least one byte must be available /" That is not how the Arduino Wire library works.

The Wire.requestFrom() does the whole I2C session and that function itself is blocking. It only returns when the I2C session has completely finished. After that, the received data is in a buffer in the Wire library. The Wire.read() and Wire.available() operate on that buffer.

So there is no need to wait for something. The data is in the buffer, or not.

Example to check if there was data:

  int n = Wire.requestFrom(0x6f, length);// request length bytes from slave device and end the transmission after this
  if(n==(int)length)    // test if the data was received
  {
    for(i=0;i<length;i++)
    {
      buffer[i] = Wire.read();  // the data is there for sure, because that was tested
    }
  }
  else
  {
    // return some kind of error ?
  }

After a Wire.requestFrom(), there is no need to wait for something. I call that common mistake number 1. See also my alternative explanation of the Wire library.

NewhavenDisplay / EVE-TFT-Modules

Usage of Arduino Wire library #2