Qwiic pHAT for Raspberry Pi Hookup Guide

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Contributors: bboyho, Englandsaurus
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I2C on Raspberry Pi

OS and Library Install

If you're starting from scratch, with a blank microSD card, you'll want to install Raspbian. If you've already got a working Raspbian system, skip ahead to step 3.

  1. Download the NOOBS image. As of this writing, it's at version 2.4.4.
  2. Follow the official installation instructions.
  3. Follow the Wiring Pi Instructions to get git, update and upgrade your Rasbpian packages, then install WiringPi.

Be patient -- each of these steps takes a while.

Once you've got wiringPi installed, run the gpio commands shown below.

language:bash
>gpio -v
>gpio readall

It should respond with some information about the wiringPi version and the Pi that its running on, then draw a table illustrating the configuration for the pins in the 40-pin connector.

Configuration

Like the SPI peripheral, I2C is not turned on by default. Again, we can use raspi-config to enable it.

  1. Run sudo raspi-config.
  2. Use the down arrow to select 5 Interfacing Options
  3. Arrow down to P5 I2C.
  4. Select yes when it asks you to enable I2C
  5. Select OK and then Finish

Once you return to terminal, enter this command:

language:bash
>ls /dev/*i2c*

The Pi should respond with:

language:bash
/dev/i2c-1

Which represents the user-mode I2C interface.

Utilities

There is a set of command-line utility programs that can help get an I2C interface working. You can get them with the apt package manager.

language:bash
sudo apt-get install -y i2c-tools

In particular, the i2cdetect program will probe all the addresses on a bus, and report whether any devices are present. Call i2cdetect -y 1 to probe the first I2C bus, which is what the Qwiic pHAT is connected to.

language:bash
pi@raspberrypi:~/$ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: 60 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

This map indicates that there is a peripheral at address 0x60. We can read and write its registers using the i2cget, i2cset and i2cdump commands.