Wire (I2C)


Wire.requestFrom, requestFrom

Used by the master to request bytes from a slave device. The bytes may then be retrieved with the available() and read() functions.

Wire.requestFrom(address, quantity);
Wire.requestFrom(address, quantity, stop);


  • address: the 7-bit address of the device to request bytes from
  • quantity: the number of bytes to request (maximum 32 unless acquireWireBuffer() is used, see below)
  • stop: boolean. true will send a stop message after the request, releasing the bus. false will continually send a restart after the request, keeping the connection active. The bus will not be released, which prevents another master device from transmitting between messages. This allows one master device to send multiple transmissions while in control. If no argument is specified, the default value is true.

Returns: byte : the number of bytes returned from the slave device. If a timeout occurs, will return 0.

Since 1.5.0:

Instead of passing address, quantity, and/or stop, a WireTransmission object can be passed to Wire.requestFrom() allowing the address and optional parameters such as a timeout to be set. I2C_ADDRESS is a constant specifying the Wire address (0-0x7e) for your specific I2C device.