Reading data from Si7021 temperature and humidity sensor using Raspberry Pi

The Si7021is an excellent little device for measuring temperature and humidity, communicating with the host controller over the I2C bus. This is a quick tutorial on using the Raspberry Pi to talk to this device. If you are unfamiliar with the conceptual framework of I2C or how to enable I2C access on the Raspberry Pi, I suggest starting here. Otherwise, let’s jump in. You are probably working with the device mounted on a breakout board.

Using the Raspberry Pi to communicate over the I2C bus using C

I recently wrote about using the excellent bcm2835 library to communicate with peripheral devices over the SPI bus using C. In this post, I’ll talk about using the same library to communicate over the I2C bus. Nothing particularly fancy, but you’ll need to pay careful attention to the datasheet of the device we’re using. TheTSL2561 is a sophisticated little light sensor that has a very high dynamic range and is available on a breakout board from Adafruit.

Implementing ADC using Raspberry Pi and MCP3008

Several years ago I wrote about adding analog-to-digital capabilities to the Raspberry Pi. At that time, I used an ATtinyx61 series MCU to provide ADC capabilities, communicating with the RPi via an I2C interface. In retrospect it was much more complicated than necessary. What follows is an attempt to re-do that project using an MCP3008, a 10 bit ADC that communicates on the SPI bus. MCP3008 device The MCP3008 is an 8-channel 10-bit ADC with an SPI interface^[Datasheet can be found here.