Keep that in mind when we start hooking up our Raspberry Pi and Arduino. This concept is very important to understand when interfacing devices with mixed logic levels.Īnother important concept is that it is the Master that determines the logic voltage level. These resistors pull the logic and clock levels up to the level of the VCC reference voltage.
The arrangement of master and slaves(s) is illustrated below. In many arrangements, this voltage is also used to power the slave device. VCC – This is the logic-level voltage reference, typically either 5-volts or 3.3.-volts.This provides the clock signal to synchronize the data on the SDA line. This is a bidirectional data line, handling all communications between the master and slave(s). An I2C circuit consists of one bus “Master” and one or more bus “Slaves”.
Pi arduino i2c example two way data communication serial#
I2C operationĪs a quick recap I2C, or the ”Inter-Integrated Circuit Bus”, is a method of exchanging serial data between two or more devices. If you just need a quick refresher then please read on. If you need a detailed explanation about the I2C bus please see the first article in this series. I2C Voltage Levelsīefore we examine the issues with mixing multiple I2C devices of different logic-levels it would be a good idea to make sure that we are familiar with the i2c bus and how it operates. In fact, there are two ways to do it.įollow along and we’ll examine both ways of interfacing a Raspberry Pi and an Arduino using the I2C bus. However, despite these voltage differences it is possible to interface the two devices. The Raspberry Pi uses 3.3-volt logic, whereas most Arduino’s (including the Arduino Uno) make use of 5-volt logic. When the clock pin changes from high to low (the falling edge of the clock), the called upon device transmits it's data back to the Arduino over the same line.īecause the 12C protocol allows for each enabled device to have it's own unique address, and as both master and slave devices to take turns communicating over a single line, it is possible for your Arduino to communicate (in turn) with many devices, or other Arduinos, while using just two pins of your microcontroller.Both the Arduino and the Raspberry Pi support I2C, however interfacing them can present a special challenge as they don’t work at the same logic voltage levels. As the clock pulse changes from low to high (known as the rising edge of the clock), a bit of information containing the address of a specific device and a request for data, is transferred from the Arduino to the I2C devices over the SDA line. The I2C protocol involves using two wires to send and receive data: a serial clock pin (SCL) that the Arduino pulses at a regular interval, and a serial data pin (SDA) over which data is sent between the two devices.
Once that message is received, it can then be viewed in the Arduino serial window. Arduino 1, the Master, is programmed to request, and then read, 6 bytes of data sent from the uniquely addressed Slave Arduino. Several functions of Arduino's Wire Library are used to accomplish this. In this example, two Arduinos are programmed to communicate with one another in a Master Reader/Slave Sender configuration via the I2C synchronous serial protocol. In some situations, it can be helpful to set up two (or more!) Arduino boards to share information with each other. Learning Examples | Foundations | Hacking | Links
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