在OpenWrt中开启树莓派I2C功能

编辑 /boot/config.txt

dtparam=i2c_arm=on
dtparam=i2c0=on
dtparam=i2c1=on
dtparam=spi=on
dtparam=i2s=on

通过opkg安装相关包

opkg install i2c-tools kmod-i2c-gpio kmod-i2c-algo-bit kmod-i2c-algo-pcf kmod-i2c-bcm2835 kmod-i2c-core kmod-i2c-gpio kmod-i2c-mux

使用i2c命令行工具测试

#!/bin/bash
ls /dev/i2c*
i2cdetect -y 1

安装python支持

opkg install python3-smbus

I2C LCD示例代码

#!/usr/bin/python
import smbus
import time
import atexit

# Define some device parameters
I2C_ADDR    = 0x27 # I2C device address
LCD_WIDTH = 16     # Maximum characters per line

# Define some device constants
LCD_CHR = 1 # Mode - Sending data
LCD_CMD = 0 # Mode - Sending command

LCD_LINE_1 = 0x80 # LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 # LCD RAM address for the 2nd line
LCD_LINE_3 = 0x94 # LCD RAM address for the 3rd line
LCD_LINE_4 = 0xD4 # LCD RAM address for the 4th line

LCD_BACKLIGHT    = 0x08    # On
#LCD_BACKLIGHT = 0x00    # Off

ENABLE = 0b00000100 # Enable bit

# Timing constants
E_PULSE = 0.0005
E_DELAY = 0.0005

#Open I2C interface
#bus = smbus.SMBus(0)    # Rev 1 Pi uses 0
bus = smbus.SMBus(1) # Rev 2 Pi uses 1

def lcd_init():
    # Initialise display
    lcd_byte(0x33,LCD_CMD) # 110011 Initialise
    lcd_byte(0x32,LCD_CMD) # 110010 Initialise
    lcd_byte(0x06,LCD_CMD) # 000110 Cursor move direction
    lcd_byte(0x0C,LCD_CMD) # 001100 Display On,Cursor Off, Blink Off
    lcd_byte(0x28,LCD_CMD) # 101000 Data length, number of lines, font size
    lcd_byte(0x01,LCD_CMD) # 000001 Clear display
    time.sleep(E_DELAY)

def lcd_byte(bits, mode):
    # Send byte to data pins
    # bits = the data
    # mode = 1 for data
    #                0 for command

    bits_high = mode | (bits & 0xF0) | LCD_BACKLIGHT
    bits_low = mode | ((bits<<4) & 0xF0) | LCD_BACKLIGHT

    # High bits
    bus.write_byte(I2C_ADDR, bits_high)
    lcd_toggle_enable(bits_high)

    # Low bits
    bus.write_byte(I2C_ADDR, bits_low)
    lcd_toggle_enable(bits_low)

def lcd_toggle_enable(bits):
    # Toggle enable
    time.sleep(E_DELAY)
    bus.write_byte(I2C_ADDR, (bits | ENABLE))
    time.sleep(E_PULSE)
    bus.write_byte(I2C_ADDR,(bits & ~ENABLE))
    time.sleep(E_DELAY)

def lcd_string(message,line):
    # Send string to display

    message = message.ljust(LCD_WIDTH," ")

    lcd_byte(line, LCD_CMD)

    for i in range(LCD_WIDTH):
        lcd_byte(ord(message[i]),LCD_CHR)

def lcd_clear():
    # Clear LCD screen
    lcd_byte(0x01, LCD_CMD)

def main():
    # Main program block

    # Initialise display
    lcd_init()

    while True:

        # Send some test
        lcd_string("RPiSpy",LCD_LINE_1)
        lcd_string("I2C LCD",LCD_LINE_2)

        time.sleep(3)

        # Send some more text
        lcd_string("RPiSpy",LCD_LINE_1)
        lcd_string("I2C LCD",LCD_LINE_2)

        time.sleep(3)


if __name__ == '__main__':

    try:
        main()
    except KeyboardInterrupt:
        pass
    finally:
        #lcd_byte(0x01, LCD_CMD)
        lcd_clear()

else:
        lcd_init()
        @atexit.register
        def atexit_f():
            lcd_clear()