Wire.write(42) // Write the value that we want in register 12 Wire.write(12) // Write the register address that we want to target Wire.beginTransmission(85) // Begin communication with slave address 85 (0x55) To write a register on a slave device, you have to initiate communication with the device (slave address), write the address of the register that you wish to write, and then write the value that you wish the register to be. This is usually placed in the setup() area of your sketch. To initialize the Wire library, you will have to call the Wire.begin() function.
(Click Sketch -> Include Library -> Wire) Setup You will have to include the Wire library into your sketch to use these functions. Here we will look at some basic examples of using the Arduino as the bus master to write to and read from a slave device with the address 0x55 (85). The Wire library for Arduino is used to perform I 2C/TWI communication. These pull-up resistors are usually 4.7kΩ, but they can be anywhere from 2.2kΩ to 10kΩ depending on the needs of the system. The open-drain output is not able to drive the line to a high voltage so, a pull-up is provided to pull the line high when it is released (open state). This means that their connection is either open (not connecting the wire to anything) or draining (connecting the line to ground). The I 2C lines have to have a pull-up to Vcc because I 2C devices operate with open-drain outputs. HardwareĪll of the devices on an I 2C bus share the same Serial Data (SDA) line and the same Serial Clock (SCL).
The protocol allows for multiple master and multiple slaves, while it is more common to only have one master and multiple slaves. The protocol is a master-slave protocol, where masters control the communication and the slaves only respond. It was designed for communication with lower-speed peripheral devices on the same board. Inter-integrated Circuit serial communication, or I 2C, is a two-wire serial interface (TWI) that was invented by Phillips Semiconductor (now NXP Semiconductors).
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