树莓派怎么用Python实现i2c
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首先树莓派得安装 python-smbus, i2c-tools,
然后修改文件：sudo nano /etc/modules，添加上 i2c-bcm2708 和i2c-dev 这两行，Raspbian还需要在raspi-config中激活i2c.
用 sudo i2cdetect -y 1 查看设备地址，
例子1：LCD2004，设备地址 为0x27；
先写个驱动调用程序 i2c_driver_lcd.py
import smbus from time import * # LCD Address ADDRESS = 0x27 # commands LCD_CLEARDISPLAY = 0x01 LCD_RETURNHOME = 0x02 LCD_ENTRYMODESET = 0x04 LCD_DISPLAYCONTROL = 0x08 LCD_CURSORSHIFT = 0x10 LCD_FUNCTIONSET = 0x20 LCD_SETCGRAMADDR = 0x40 LCD_SETDDRAMADDR = 0x80 # flags for display entry mode LCD_ENTRYRIGHT = 0x00 LCD_ENTRYLEFT = 0x02 LCD_ENTRYSHIFTINCREMENT = 0x01 LCD_ENTRYSHIFTDECREMENT = 0x00 # flags for display on/off control LCD_DISPLAYON = 0x04 LCD_DISPLAYOFF = 0x00 LCD_CURSORON = 0x02 LCD_CURSOROFF = 0x00 LCD_BLINKON = 0x01 LCD_BLINKOFF = 0x00 # flags for display/cursor shift LCD_DISPLAYMOVE = 0x08 LCD_CURSORMOVE = 0x00 LCD_MOVERIGHT = 0x04 LCD_MOVELEFT = 0x00 # flags for function set LCD_8BITMODE = 0x10 LCD_4BITMODE = 0x00 LCD_2LINE = 0x08 LCD_1LINE = 0x00 LCD_5x10DOTS = 0x04 LCD_5x8DOTS = 0x00 # flags for backlight control LCD_BACKLIGHT = 0x08 LCD_NOBACKLIGHT = 0x00 # set init LCD BACKLIGHT ON or OFF def lcd_backlight(lcdbl=1): if lcdbl == 0 : return LCD_NOBACKLIGHT return LCD_BACKLIGHT En = 0b00000100 # Enable bit Rw = 0b00000010 # Read/Write bit Rs = 0b00000001 # Register select bit class lcd(object): #initializes objects and lcd def __init__(self,lcd_bl,port=1): self.addr = ADDRESS self.bus = smbus.SMBus(port) self.lcd_bl = lcd_bl self.lcd_write(0x03) self.lcd_write(0x03) self.lcd_write(0x03) self.lcd_write(0x02) self.lcd_write(LCD_FUNCTIONSET | LCD_2LINE | LCD_5x8DOTS | LCD_4BITMODE) self.lcd_write(LCD_DISPLAYCONTROL | LCD_DISPLAYON) self.lcd_write(LCD_CLEARDISPLAY) self.lcd_write(LCD_ENTRYMODESET | LCD_ENTRYLEFT) sleep(0.2) def set_lcd(self,set_lcdbl): self.lcd_bl = set_lcdbl # clocks EN to latch command def lcd_strobe(self, data): self.write_cmd(data | En | lcd_backlight(self.lcd_bl)) sleep(.0005) self.write_cmd(((data & ~En) | lcd_backlight(self.lcd_bl))) sleep(.0001) def lcd_write_four_bits(self, data): self.write_cmd(data | lcd_backlight(self.lcd_bl)) self.lcd_strobe(data) # write a command to lcd def lcd_write(self, cmd, mode=0): self.lcd_write_four_bits(mode | (cmd & 0xF0)) self.lcd_write_four_bits(mode | ((cmd << 4) & 0xF0)) # put string function def lcd_display_string(self, string, raw=1, col=1): if raw == 1: self.lcd_write(0x80+col-1) if raw == 2: self.lcd_write(0xC0+col-1) if raw == 3: self.lcd_write(0x94+col-1) if raw == 4: self.lcd_write(0xD4+col-1) for char in string: self.lcd_write(ord(char), Rs) # clear lcd and set to home def lcd_clear(self): self.lcd_write(LCD_CLEARDISPLAY) self.lcd_write(LCD_RETURNHOME) # Write a single command def write_cmd(self, cmd): self.bus.write_byte(self.addr, cmd) sleep(0.0001)
然后写个lcd_main.py
import i2c_driver_lcd as lcd_driver
from time import *
lcd = lcd_driver.lcd(0,1)#设置背光开关，port=1
lcd.lcd_display_string("hello raspberry", 1,3)
s= raw_input("input:")
lcd.set_lcd(1)#设置背光开关
lcd.lcd_display_string(s, 2, 2)例子2：hmc5883l ; 设备地址为 0x1e
先写个驱动调用程序 i2c_driver_hmc5883l.py
#!/usr/bin/env python
# vim: set fileencoding=UTF-8 :
# HMC5888L Magnetometer (Digital Compass) wrapper class
# Based on https://bitbucket.org/thinkbowl/i2clibraries/src/14683feb0f96,
# but uses smbus rather than quick2wire and sets some different init
# params.
import smbus
import math
class hmc5883l:
__scales = {
0.88: [0, 0.73],
1.30: [1, 0.92],
1.90: [2, 1.22],
2.50: [3, 1.52],
4.00: [4, 2.27],
4.70: [5, 2.56],
5.60: [6, 3.03],
8.10: [7, 4.35],
}
def __init__(self, port=1, address=0x1E, gauss=1.3, declination=(0,0)):
self.bus = smbus.SMBus(port)
self.address = address
(degrees, minutes) = declination
self.__declDegrees = degrees
self.__declMinutes = minutes
self.__declination = (degrees + minutes / 60) * math.pi / 180
(reg, self.__scale) = self.__scales[gauss]
self.bus.write_byte_data(self.address, 0x00, 0x70) # 8 Average, 15 Hz, normal measurement
self.bus.write_byte_data(self.address, 0x01, reg << 5) # Scale
self.bus.write_byte_data(self.address, 0x02, 0x00) # Continuous measurement
def declination(self):
return (self.__declDegrees, self.__declMinutes)
def twos_complement(self, val, len):
# Convert twos compliment to integer
if (val & (1 << len - 1)):
val = val - (1< 2 * math.pi:
headingRad -= 2 * math.pi
# Convert to degrees from radians
headingDeg = headingRad * 180 / math.pi
return headingDeg
def degrees(self, headingDeg):
degrees = math.floor(headingDeg)
minutes = round((headingDeg - degrees) * 60)
return (degrees, minutes)
def __str__(self):
(x, y, z) = self.axes()
return "Axis X: " + str(x) + "\n" \
"Axis Y: " + str(y) + "\n" \
"Axis Z: " + str(z) + "\n" \
"Declination: " + self.degrees(self.declination()) + "\n" \
"Heading: " + self.degrees(self.heading()) + "\n" 再写个gy273_main.py
import i2c_driver_hmc5883l as hmc5883l
import time
import sys
# http://magnetic-declination.com/Great%20Britain%20(UK)/Harrogate#
compass = hmc5883l.hmc5883l(gauss = 4.7, declination = (-2,5))
while True:
sys.stdout.write("\rHeading: " + str(compass.degrees(compass.heading())) + " ")
#sys.stdout.write("\rAxis X: " + str(str(x))
sys.stdout.flush()
time.sleep(0.5)i2c设备容易共用总线，比如上述两个i2c设备，可以接在同一个i2c总线上，但要注意LCD可能需要5V供电，而模块gy273供电VCC为3.3V。
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