3.3.5 Using I2C

By default, RDK X3 enables I2C0 on pin 40, with physical pin numbers 3 and 5, and IO voltage of 3.3V.

RDX Ultra enables I2C4 and I2C6, with physical pin numbers 3, 5, 27, and 28, and IO voltage of 3.3V.

Please refer to /app/40pin_samples/test_i2c.py for detailed information on how to use I2C.

Testing Method

• Run the test program python3 /app/40pin_samples/test_i2c.py

• List the currently enabled I2C buses

• Scan the bus to see which devices are connected to the bus by inputting the bus number

• Input the device address (in hexadecimal), and the test program will read one byte of data from that device

Test Result

Starting demo now! Press CTRL+C to exit
List of enabled I2C controllers:
/dev/i2c-0  /dev/i2c-1
Please input I2C BUS num:1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- UU -- -- -- -- 
40: 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         
Please input I2C device num(Hex):40
Read data from device 40 on I2C bus 1
read value= b'`'

Test Code

#!/usr/bin/env python3

import sys
import os
import time

# import i2cdev
from i2cdev import I2C

def i2cdevTest():
    # device, bus = 0x51, 0
    bus = input("Please input I2C BUS num:")
    os.system('i2cdetect -y -r ' + bus)
    device = input("Please input I2C device num(Hex):")
    print("Read data from device %s on I2C bus %s" % (device, bus))
    i2c = I2C(eval("0x" + device), int(bus))
    value = i2c.read(1)
    i2c.write(value)
    print("read value=", value)
    i2c.close()

if __name__ == '__main__':
    print("Starting demo now! Press CTRL+C to exit")
    print("List of enabled I2C controllers:")
    os.system('ls /dev/i2c*')
    while True:
        i2cdevTest()