How to change the I2C Frequency/Speed for Raspberry Pi 2/3

HowToChangeI2CSpeed.md

How to change the I2C Frequency/Speed for Raspberry Pi 2/3

Note: Steps 5-8 are only for verification purposes, you can skip them

1. Open /boot/config.txt file

   sudo nano /boot/config.txt

2. Find the line containing dtparam=i2c_arm=on

3. Add i2c_arm_baudrate=<new speed> (Separate with a Comma)

   dtparam=i2c_arm=on,i2c_arm_baudrate=400000

4. Reboot Raspberry Pi

5. Create a simple test script to verify the speed

• Switch to home directory cd ~
• Create shell script nano i2cspeed.sh
• Copy and paste the following lines of code

#!/bin/bash
var="$(xxd /sys/class/i2c-adapter/i2c-1/of_node/clock-frequency | awk -F': ' '{print $2}')"
var=${var//[[:blank:].\}]/}
printf "%d\n" 0x$var

6. Change file permissions

chmod +x i2cspeed.sh

7. Execute test script

./i2cspeed.sh

8. Verify that the value is the correct setting

pi@rpi-dev:~ $ ./i2cspeed.sh 
400000

Source: Raspberry Pi Forums

It will be better, if the file 'i2cspeed.sh' is changed to the followings,

#!/bin/bash
var="$(xxd -ps /sys/class/i2c-adapter/i2c-1/of_node/clock-frequency)"
var=${var//[[:blank:].\}]/}
printf "%d\n" 0x$var