The I2C protocol involves using two lines to send and receive data: a serial clock pin (SCL) that the Arduino or Genuino Master board pulses at a regular interval, and a serial data pin (SDA) over which data is sent between the two devices.Īs the clock line changes from low to high (known as the rising edge of the clock pulse), a single bit of information - that will form in sequence the address of a specific device and a a command or data - is transferred from the board to the I2C device over the SDA line. Once that message is received, it can then be viewed in the Slave board's serial monitor window opened on the USB connected computer running the Arduino Software (IDE). In this example, two boards are programmed to communicate with one another in a Master Writer/Slave Receiver configuration via the I2C synchronous serial protocol.Īrduino 1, the Master, is programmed to send 6 bytes of data every half second to a uniquely addressed Slave. In some situations, it can be helpful to set up two (or more!) Arduino or Genuino boards to share information with each other. This makes the linker happy and allows your program to build.Wire library - Master Writer/Slave Receiver

the program file that contains your start and loop functions). The magic thing to know is that if any of your libraries use Wire.h or SPI.h you must Include them in the main source file (i.e. It’s one of those horrible situations where you have to know the “magic” trick to make it work. I’ve had this before, it is very frustrating. The compiler kept complaining about the Wire.h and SPI.h libraries not being available. I’d added the AdaFruit libraries and at that point my program broke. I’ve been creating a “Connected Little Boxes” driver for the BME280 environmental sensor (a personal favourite of mine). I hardly ever use them personally, I rely on people much cleverer than me to create libraries that I can use to talk to the hardware I want to use. They’re used by programs to communicate with devices over the I2C and SPI busses.

The Wire.h and SPI.h Arduino libraries are kind of important.

Arduino wire library