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3.3.5 I2C Application

By default, the RDX S100 enables I2C5 (physical pins 3 and 5) and I2C4 (physical pins 27 and 28) on the 40-pin header, with an I/O voltage of 3.3V.

info
  • On the 40-pin header, you need to toggle the DIP switch to select between I2C5 and UART2. For specific details, please refer to the figure below:

image-rdk_100_funcreuse_40pin

For pin definitions, please refer to Pin Configuration and Definitions.

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

tip

The pins mentioned below are provided as examples only. Port values may differ across platforms; always verify against your actual hardware setup. Alternatively, you can directly use the code under the /app/40pin_samples/ directory, which has already been verified on the board.

Testing Method​

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

  • First, list all currently enabled I2C buses in the system.

  • Enter a bus number to scan and identify which peripherals are connected to that bus.

  • Input the peripheral device address (in hexadecimal). The test program will then read one byte of data from the specified device.

Execution Output​

root@ubuntu:/app/40pin_samples# ./test_i2c.py
Starting demo now! Press CTRL+C to exit
List of enabled I2C controllers:
/dev/i2c-0  /dev/i2c-1  /dev/i2c-2  /dev/i2c-3  /dev/i2c-4  /dev/i2c-5
Please input I2C BUS num:0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: UU -- -- -- UU -- -- UU -- -- -- UU -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- 44 -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
Please input I2C device num(Hex):44
Read data from device 44 on I2C bus 0
read value= b'\x00'

Test Code​

#!/usr/bin/env python3

import sys
import signal
import os
import time

# Import i2cdev
from i2cdev import I2C

def signal_handler(signal, frame):
    sys.exit(0)

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__':
    signal.signal(signal.SIGINT, signal_handler)
    print("Starting demo now! Press CTRL+C to exit")
    print("List of enabled I2C controllers:")
    os.system('ls /dev/i2c*')
    while True:
        i2cdevTest()
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