Bare-Metal STM32: Using The I2C Bus In Master-Transceiver Mode

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2022-05-12 07:30:09

As one of the most popular buses today for on- and inter-board communication within systems, there’s a good chance you’ll end up using it with an embedded system. I2C offers a variety of speeds while requiring only two wires (clock and data), which makes it significantly easier to handle than alternatives, such as SPI. Within the STM32 family of MCUs, you will find at least one I2C peripheral on each device.

As a shared, half-duplex medium, I2C uses a rather straightforward call-and-response design, where one device controls the clock, and other devices simply wait and listen until their fixed address is sent on the I2C bus. While configuring an STM32 I2C peripheral entails a few steps, it is quite painless to use afterwards, as we will see in this article.

Assuming that the receiving devices like sensors are wired up properly with the requisite pull-up resistors in place, next we can begin to configure the MCU’s I2C peripheral. We’ll be using the STM32F042 as the target MCU, but other STM32 families are rather similar from an I2C perspective. We’ll also use CMSIS-style peripheral and register references.