if i upload the continuous reading sketch to the arduino uno using a tentacle mini with 2 boards attached a PH and an ORP i get continuous data as I would expect. However when I try the interactive example sending a command 99:r I get the associated board to flash a red LED and in the serial monitor I get command failed.. Please help as for my use Im going to want to issue a command for a reading via serial

The Arduino Wire library is used incorrectly in the next files:

1. tentacle-examples/arduino/asynchronous/i2c_asynchronous/i2c_asynchronous.ino
2. tentacle-examples/arduino/asynchronous/i2c_asynchronous_yun/i2c_asynchronous_yun.ino
3. tentacle-examples/arduino/continuous/i2c_continuous/i2c_continuous.ino
4. tentacle-examples/arduino/continuous/i2c_continuous_yun/i2c_continuous_yun.ino
5. tentacle-examples/arduino/interactive/i2c_interactive/i2c_interactive.ino
6. tentacle-examples/arduino/interactive/i2c_interactive_yun/i2c_interactive_yun.ino
7. tentacle-examples/arduino/interactive/mixed_uart_i2c/mixed_uart_i2c.ino
8. tentacle-examples/arduino/interactive/mixed_uart_i2c_yun/mixed_uart_i2c_yun.ino
9. tentacle-examples/arduino/tentacle-setup/tentacle_setup/tentacle_setup.ino
10. tentacle-examples/arduino/tentacle-setup/tentacle_setup_yun/tentacle_setup_yun.ino
11. tentacle-examples/arduino/tentacle-setup/tentacle_setup_i2c_only/tentacle_setup_i2c_only.ino

The maximum number of bytes to read is 32 for a Wire.requestFrom(). I see 48 many times. The buffer in the Wire library is 32 bytes.

The Wire.endTransmission() may not be used after a Wire.requestFrom(). The Wire.requestFrom() is a complete I2C transaction on its own.
The Wire.endTransmission() on the other hand may not be used on its own to do something, it can only be used when writing data with Wire.beginTransmission() and Wire.write().
When the length of the data is unknown, and no more data is needed, then don't read more data. Nothing else is needed.

When the Wire.requestFrom() returns, the I2C transaction on the bus has completely finished and the received data is waiting in a buffer in the Wire library. That data can be read or not.

There is therefor also no need to read any remaining data from the buffer to "clear" it. If there once was a bug in that situation with the Arduino Zero, that should have been solved long ago.