On the Arduino Mega, SDA is digital pin 20 and SCL is digital pin 21 (they are marked SDA and SCL on the board itself). Analog port 5 (A5) = SCL (serial clock).On the Arduino Uno the pins you need are: More information about the Arduino Two-Wire interface at: Address 0 is reserved as a 'broadcast' address, addresses 1 to 7 are reserved for other purposes, and addresses 120 to 127 are reserved for future use.īecause of this you could have an LCD screen (say) at address 10, a keyboard at address 11, and so on. Each device needs to have a unique address in the range 8 to 119. This is because the devices are 'addressable'.

The Two-Wire interface is extremely useful for connecting multiple devices, as they can all share the same two pins (plus a ground return). A lot of the details however will be of more general interest. This post describes how the I2C (Inter-Integrated Circuit, or 'Two-Wire') interface works, with particular reference to the Arduino Uno which is based on the ATmega328P microprocessor chip. This page can be quickly reached from the link: Code samples in the reference are released into the public domain.A summary of everything shown below is available further down this page: The text of the Arduino reference is licensed under aĬreative Commons Attribution-ShareAlike 3.0 License. shift the value one bit to the right), yielding an address between 0 and 127.Ĭorrections, suggestions, and new documentation should be posted to the Forum. If you have a datasheet or sample code that uses 8 bit address, you'll want to drop the low bit (i.e. The Wire library uses 7 bit addresses throughout. 7 bits identify the device, and the eighth bit determines if it's being written to or read from. There are both 7- and 8-bit versions of I2C addresses. Because of this, send() and receive() have been replaced with read() and write(). On the Arduino Mega, SDA is digital pin 20 and SCL is 21.Īs of Arduino 1.0, the library inherits from the Stream functions, making it consistent with other read/write libraries. On most Arduino boards, SDA (data line) is on analog input pin 4, and SCL (clock line) is on analog input pin 5. This library allows you to communicate with I2C / TWI devices. Reference Language | Libraries | Comparison | Changes

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