Mixing Logic Levelsĥ-volt logic, also sometimes referred to as “TTL logic”, has been around for many decades. 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”. 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. 
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.
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