[Raspberry Pi]PCF8574扩展IO口实现I2C转LCD1602（Python）

dvd1478

上次很偶然的秒到了I2C转LCD1602，
秒到IIC控制LCD1602转换版到货啦！
https://www.cirmall.com/bbs/forum ... 45305&fromuid=23447


LCD1602多引脚面对Raspberry Pi 引脚有限的情况，就显得由为重要。

先来来Python 的实现方法，主要是利用python-smbus
方案方法
sudo apt-get install python-smbus
sudo apt-get install i2c-tools


MCP8574 的代码如下Qtgz_PCF8574.py

1. from Qtgz_I2C import Qtgz_I2C
   
2. import smbus
   
3. import time
   
4. 
   
5. class Qtgz_MCP8574(object):
   
6.     OUTPUT = 0
   
7.     INPUT = 1
   
8. 
   
9.     def __init__(self, address, num_gpios, busnum=-1):
   
10.         assert num_gpios >= 0 and num_gpios <= 8, "Number of GPIOs must be between 0 and 16"
    
11.         self.i2c = Qtgz_I2C(address=address, busnum=busnum)
    
12.         self.address = address
    
13.         self.num_gpios = num_gpios
    
14. 
    
15.     def _changebit(self, bitmap, bit, value):
    
16.         assert value == 1 or value == 0, "Value is %s must be 1 or 0" % value
    
17.         if value == 0:
    
18.             return bitmap & ~(1 << bit)
    
19.         elif value == 1:
    
20.             return bitmap | (1 << bit)
    
21. 
    
22.     def _readandchangepin(self, pin, value, currvalue = None):
    
23.         assert pin >= 0 and pin < self.num_gpios, "Pin number %s is invalid, only 0-%s are valid" % (pin, self.num_gpios)
    
24.         #assert self.direction & (1 << pin) == 0, "Pin %s not set to output" % pin
    
25.         if not currvalue:
    
26.              currvalue = self.i2c.readRaw8()
    
27.         newvalue = self._changebit(currvalue, pin, value)
    
28.         self.i2c.writeRaw8(newvalue)
    
29.         return newvalue
    
30. 
    
31.     def config(self, pin, mode):
    
32.         if self.num_gpios <= 8:
    
33.             self.direction = self._readandchangepin(pin, mode)
    
34.         return self.direction
    
35. 
    
36.     def output(self, pin, value):
    
37.         if self.num_gpios <= 8:
    
38.             self.outputvalue = self._readandchangepin(pin, value, self.i2c.readRaw8())
    
39.         return self.outputvalue
    
40. 
    
41.     def input(self, pin):
    
42.         assert pin >= 0 and pin < self.num_gpios, "Pin number %s is invalid, only 0-%s are valid" % (pin, self.num_gpios)
    
43.         assert self.direction & (1 << pin) != 0, "Pin %s not set to input" % pin
    
44.         if self.num_gpios <= 8:
    
45.             value = self.i2c.readRaw8()
    
46.         return value & (1 << pin)
    
47. 
    
48.     def readU8(self):
    
49.         result = self.i2c.readRaw8()
    
50.         return(result)
    
51. 
    
52.     def readS8(self):
    
53.         result = self.i2c.readRaw8()
    
54.         if (result > 127): result -= 256
    
55.         return result
    
56. 
    
57.     def write8(self, value):
    
58.         self.i2c.writeRaw8(value)
    
59. 
    
60. class PCF8574_GPIO(object):
    
61.     OUT = 0
    
62.     IN = 1
    
63.     BCM = 0
    
64.     BOARD = 0
    
65.     def __init__(self, busnum, address, num_gpios):
    
66.         self.chip = Qtgz_MCP8574(address, num_gpios, busnum)
    
67.     def setmode(self, mode):
    
68.         # do nothing
    
69.         pass
    
70.     def setup(self, pin, mode):
    
71.         self.chip.config(pin, mode)
    
72.     def input(self, pin):
    
73.         return self.chip.input(pin)
    
74.     def output(self, pin, value):
    
75.         self.chip.output(pin, value)
    
76. 
    
77. if __name__ == '__main__':
    
78.     # ***************************************************
    
79.     # Set num_gpios to 8 for MCP8574
    
80.     # ***************************************************
    
81.     mcp = Qtgz_MCP8574(address = 0x27, num_gpios = 8) # MCP8574
    
82. 
    
83.     mcp.config(3, mcp.OUTPUT)
    
84. 
    
85.     # Set pin 3 to input with the pullup resistor enabled
    
86.     #mcp.config(3, mcp.INPUT)
    
87. 
    
88.     # Read input pin and display the results
    
89.     #print "Pin 3 = %d" % (mcp.input(3) >> 3)
    
90. 
    
91.     # Python speed test on output 3 toggling at max speed
    
92.     print "Starting blinky on pin 3 (CTRL+C to quit)"
    
93.     while (True):
    
94.       mcp.output(3, 1)  # Pin 0 High
    
95.       time.sleep(1);
    
96.       mcp.output(3, 0)  # Pin 0 Low
    
97.       time.sleep(1);

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LCD1602 的代码

1. from time import sleep
   
2. 
   
3. 
   
4. class Adafruit_CharLCD(object):
   
5. 
   
6.     # commands
   
7.     LCD_CLEARDISPLAY        = 0x01
   
8.     LCD_RETURNHOME          = 0x02
   
9.     LCD_ENTRYMODESET        = 0x04
   
10.     LCD_DISPLAYCONTROL      = 0x08
    
11.     LCD_CURSORSHIFT         = 0x10
    
12.     LCD_FUNCTIONSET         = 0x20
    
13.     LCD_SETCGRAMADDR        = 0x40
    
14.     LCD_SETDDRAMADDR        = 0x80
    
15. 
    
16.     # flags for display entry mode
    
17.     LCD_ENTRYRIGHT          = 0x00
    
18.     LCD_ENTRYLEFT           = 0x02
    
19.     LCD_ENTRYSHIFTINCREMENT = 0x01
    
20.     LCD_ENTRYSHIFTDECREMENT = 0x00
    
21. 
    
22.     # flags for display on/off control
    
23.     LCD_DISPLAYON           = 0x04
    
24.     LCD_DISPLAYOFF          = 0x00
    
25.     LCD_CURSORON            = 0x02
    
26.     LCD_CURSOROFF           = 0x00
    
27.     LCD_BLINKON             = 0x01
    
28.     LCD_BLINKOFF            = 0x00
    
29. 
    
30.     # flags for display/cursor shift
    
31.     LCD_DISPLAYMOVE         = 0x08
    
32.     LCD_CURSORMOVE          = 0x00
    
33. 
    
34.     # flags for display/cursor shift
    
35.     LCD_DISPLAYMOVE         = 0x08
    
36.     LCD_CURSORMOVE          = 0x00
    
37.     LCD_MOVERIGHT           = 0x04
    
38.     LCD_MOVELEFT            = 0x00
    
39. 
    
40.     # flags for function set
    
41.     LCD_8BITMODE            = 0x10
    
42.     LCD_4BITMODE            = 0x00
    
43.     LCD_2LINE               = 0x08
    
44.     LCD_1LINE               = 0x00
    
45.     LCD_5x10DOTS            = 0x04
    
46.     LCD_5x8DOTS             = 0x00
    
47. 
    
48.     def __init__(self, pin_rs=25, pin_e=24, pins_db=[23, 17, 21, 22], GPIO=None):
    
49.         # Emulate the old behavior of using RPi.GPIO if we haven't been given
    
50.         # an explicit GPIO interface to use
    
51.         if not GPIO:
    
52.             import RPi.GPIO as GPIO
    
53.             GPIO.setwarnings(False)
    
54.         self.GPIO = GPIO
    
55.         self.pin_rs = pin_rs
    
56.         self.pin_e = pin_e
    
57.         self.pins_db = pins_db
    
58. 
    
59.         self.GPIO.setmode(GPIO.BCM) #GPIO=None use Raspi PIN in BCM mode
    
60.         self.GPIO.setup(self.pin_e, GPIO.OUT)
    
61.         self.GPIO.setup(self.pin_rs, GPIO.OUT)
    
62. 
    
63.         for pin in self.pins_db:
    
64.             self.GPIO.setup(pin, GPIO.OUT)
    
65. 
    
66.         self.write4bits(0x33)  # initialization
    
67.         self.write4bits(0x32)  # initialization
    
68.         self.write4bits(0x28)  # 2 line 5x7 matrix
    
69.         self.write4bits(0x0C)  # turn cursor off 0x0E to enable cursor
    
70.         self.write4bits(0x06)  # shift cursor right
    
71. 
    
72.         self.displaycontrol = self.LCD_DISPLAYON | self.LCD_CURSOROFF | self.LCD_BLINKOFF
    
73. 
    
74.         self.displayfunction = self.LCD_4BITMODE | self.LCD_1LINE | self.LCD_5x8DOTS
    
75.         self.displayfunction |= self.LCD_2LINE
    
76. 
    
77.         # Initialize to default text direction (for romance languages)
    
78.         self.displaymode = self.LCD_ENTRYLEFT | self.LCD_ENTRYSHIFTDECREMENT
    
79.         self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)  # set the entry mode
    
80. 
    
81.         self.clear()
    
82. 
    
83.     def begin(self, cols, lines):
    
84.         if (lines > 1):
    
85.             self.numlines = lines
    
86.             self.displayfunction |= self.LCD_2LINE
    
87. 
    
88.     def home(self):
    
89.         self.write4bits(self.LCD_RETURNHOME)  # set cursor position to zero
    
90.         self.delayMicroseconds(3000)  # this command takes a long time!
    
91. 
    
92.     def clear(self):
    
93.         self.write4bits(self.LCD_CLEARDISPLAY)  # command to clear display
    
94.         self.delayMicroseconds(3000)  # 3000 microsecond sleep, clearing the display takes a long time
    
95. 
    
96.     def setCursor(self, col, row):
    
97.         self.row_offsets = [0x00, 0x40, 0x14, 0x54]
    
98.         if row > self.numlines:
    
99.             row = self.numlines - 1  # we count rows starting w/0
    
100.         self.write4bits(self.LCD_SETDDRAMADDR | (col + self.row_offsets[row]))
     
101. 
     
102.     def noDisplay(self):
     
103.         """ Turn the display off (quickly) """
     
104.         self.displaycontrol &= ~self.LCD_DISPLAYON
     
105.         self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)
     
106. 
     
107.     def display(self):
     
108.         """ Turn the display on (quickly) """
     
109.         self.displaycontrol |= self.LCD_DISPLAYON
     
110.         self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)
     
111. 
     
112.     def noCursor(self):
     
113.         """ Turns the underline cursor off """
     
114.         self.displaycontrol &= ~self.LCD_CURSORON
     
115.         self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)
     
116. 
     
117.     def cursor(self):
     
118.         """ Turns the underline cursor on """
     
119.         self.displaycontrol |= self.LCD_CURSORON
     
120.         self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)
     
121. 
     
122.     def noBlink(self):
     
123.         """ Turn the blinking cursor off """
     
124.         self.displaycontrol &= ~self.LCD_BLINKON
     
125.         self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)
     
126. 
     
127.     def blink(self):
     
128.         """ Turn the blinking cursor on """
     
129.         self.displaycontrol |= self.LCD_BLINKON
     
130.         self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol)
     
131. 
     
132.     def DisplayLeft(self):
     
133.         """ These commands scroll the display without changing the RAM """
     
134.         self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVELEFT)
     
135. 
     
136.     def scrollDisplayRight(self):
     
137.         """ These commands scroll the display without changing the RAM """
     
138.         self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVERIGHT)
     
139. 
     
140.     def leftToRight(self):
     
141.         """ This is for text that flows Left to Right """
     
142.         self.displaymode |= self.LCD_ENTRYLEFT
     
143.         self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)
     
144. 
     
145.     def rightToLeft(self):
     
146.         """ This is for text that flows Right to Left """
     
147.         self.displaymode &= ~self.LCD_ENTRYLEFT
     
148.         self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)
     
149. 
     
150.     def autoscroll(self):
     
151.         """ This will 'right justify' text from the cursor """
     
152.         self.displaymode |= self.LCD_ENTRYSHIFTINCREMENT
     
153.         self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)
     
154. 
     
155.     def noAutoscroll(self):
     
156.         """ This will 'left justify' text from the cursor """
     
157.         self.displaymode &= ~self.LCD_ENTRYSHIFTINCREMENT
     
158.         self.write4bits(self.LCD_ENTRYMODESET | self.displaymode)
     
159. 
     
160.     def write4bits(self, bits, char_mode=False):
     
161.         """ Send command to LCD """
     
162.         self.delayMicroseconds(1000)  # 1000 microsecond sleep
     
163.         bits = bin(bits)[2:].zfill(8)
     
164.         self.GPIO.output(self.pin_rs, char_mode)
     
165.         for pin in self.pins_db:
     
166.             self.GPIO.output(pin, False)
     
167.         for i in range(4):
     
168.             if bits[i] == "1":
     
169.                 self.GPIO.output(self.pins_db[::-1][i], True)
     
170.         self.pulseEnable()
     
171.         for pin in self.pins_db:
     
172.             self.GPIO.output(pin, False)
     
173.         for i in range(4, 8):
     
174.             if bits[i] == "1":
     
175.                 self.GPIO.output(self.pins_db[::-1][i-4], True)
     
176.         self.pulseEnable()
     
177. 
     
178.     def delayMicroseconds(self, microseconds):
     
179.         seconds = microseconds / float(1000000)  # divide microseconds by 1 million for seconds
     
180.         sleep(seconds)
     
181. 
     
182.     def pulseEnable(self):
     
183.         self.GPIO.output(self.pin_e, False)
     
184.         self.delayMicroseconds(1)       # 1 microsecond pause - enable pulse must be > 450ns
     
185.         self.GPIO.output(self.pin_e, True)
     
186.         self.delayMicroseconds(1)       # 1 microsecond pause - enable pulse must be > 450ns
     
187.         self.GPIO.output(self.pin_e, False)
     
188.         self.delayMicroseconds(1)       # commands need > 37us to settle
     
189. 
     
190.     def message(self, text):
     
191.         """ Send string to LCD. Newline wraps to second line"""
     
192.         for char in text:
     
193.             if char == '\n':
     
194.                 self.write4bits(0xC0)  # next line
     
195.             else:
     
196.                 self.write4bits(ord(char), True)
     
197. 
     
198. 
     
199. if __name__ == '__main__':
     
200.     lcd = Adafruit_CharLCD()
     
201.     lcd.clear()
     
202.     lcd.message("  Adafruit 16x2\n  Standard LCD")

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实现代码如下，打印内部温度，内存使用情况

1. #!/usr/bin/python
   
2. # -*- coding: utf-8 -*-
   
3. from Adafruit_CharLCD import Adafruit_CharLCD
   
4. from Qtgz_PCF8574 import PCF8574_GPIO
   
5. 
   
6. from subprocess import *
   
7. from time import sleep, strftime
   
8. from datetime import datetime
   
9. import commands
   
10. 
    
11. 
    
12. def get_cpu_temp():
    
13.     tmp = open('/sys/class/thermal/thermal_zone0/temp')
    
14.     cpu = tmp.read()
    
15.     tmp.close()
    
16.     return '{:.2f}'.format( float(cpu)/1000 ) + ' C'
    
17. 
    
18. def get_gpu_temp():
    
19.     tmp = commands.getoutput('vcgencmd measure_temp|awk -F= \'{print $2}\'').replace('\'C','')
    
20.     gpu = float(tmp)
    
21.     return '{:.2f}'.format( gpu ) + ' C'
    
22. 
    
23. def get_time_now():
    
24.     return datetime.now().strftime('    %H:%M:%S\n   %Y-%m-%d')
    
25. 
    
26. def get_ip_info():
    
27.     return commands.getoutput('ifconfig wlan0|grep inet|awk -Faddr: \'{print $2}\'|awk \'{print $1}\'')
    
28. 
    
29. def get_mem_info():
    
30.     total= commands.getoutput('free -m|grep Mem:|awk \'{print $2}\'')  
    
31.     free = commands.getoutput('free -m|grep cache:|awk \'{print $4}\'')
    
32.     return 'MEM:\n    ' + free +' / '+ total +' M'
    
33. 
    
34. 
    
35. bus = 1         # Note you need to change the bus number to 0 if running on a revision 1 Raspberry Pi.
    
36. address = 0x27  # I2C address of the PCF8574 chip.
    
37. gpio_count = 8  # Number of GPIOs exposed by the PCF8574 chip, should be 8 or 16 depending on chip.
    
38. 
    
39. # Create PCF8574 GPIO adapter.
    
40. mcp = PCF8574_GPIO(bus, address, gpio_count)
    
41. # Create LCD, passing in MCP GPIO adapter.
    
42. lcd = Adafruit_CharLCD(pin_rs=0, pin_e=2, pins_db=[4,5,6,7], GPIO=mcp)
    
43. 
    
44. 
    
45. if __name__ == '__main__':
    
46. 
    
47.     while(1):
    
48.         lcd.clear()
    
49.         lcd.message( get_ip_info() )
    
50.         sleep(1)
    
51.          
    
52.         lcd.clear()
    
53.         lcd.message( get_time_now() )
    
54.         sleep(1)
    
55.          
    
56.         lcd.clear()
    
57.         lcd.message( get_mem_info() )
    
58.         sleep(1)
    
59. 
    
60.         lcd.clear()
    
61.         lcd.message( 'CPU: ' + get_cpu_temp()+'\n' )
    
62.         lcd.message( 'GPU: ' + get_gpu_temp() )
    
63.         sleep(1)

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效果如下

斑斑

楼主真厉害，用C语言和Python都实现了！

陆小六小六

请问lZ，from Qtgz_I2C import Qtgz_I2C这个模块在哪里啊。。

盛京老驴

I2C很神奇的,只是我是硬件小白!!!