夏任务105：做一个桌面温湿度计
浙江大学计算机科学与技术学院 / 课程：嵌入式系统 / 指导教师：翁恺
用RPi采集温度、湿度和气压传感器的数据，在LCD显示
前情提要：上次用了蛋疼的热敏电阻来获得温度，这次用DHT11啦～话说木有气压传感器，所以就省略气压这步了。注意，因为之前已经安装过wiringPi的库，在本篇中不再重复。关于如何驱动LCD请参考《[树莓派]桌面时钟》。
1. 连接并驱动DHT11
正确连接DHT11与树莓派，连线方法如下（此处参考了某位同学的报告～）
建立一个dht11.c的文件，贴入以下内容
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// //mydht11.c // #include <wiringPi.h> #include <stdio.h> #include <stdlib.h> typedef unsigned char uint8; typedef unsigned int uint16; typedef unsigned long uint32; #define HIGH_TIME 32 int wiringPiSetup (void) ; int pinNumber = 7; //use gpio1 to read data uint32 databuf; uint8 readSensorData(void) { uint8 crc; uint8 i; pinMode(pinNumber,OUTPUT); // set mode to output digitalWrite(pinNumber, 0); // output a high level delay(25); digitalWrite(pinNumber, 1); // output a low level pinMode(pinNumber, INPUT); // set mode to input pullUpDnControl(pinNumber,PUD_UP); delayMicroseconds(27); if(digitalRead(pinNumber)==0) //SENSOR ANS { while(!digitalRead(pinNumber)); //wait to high for(i=0;i<32;i++) { while(digitalRead(pinNumber)); //data clock start while(!digitalRead(pinNumber)); //data start delayMicroseconds(HIGH_TIME); databuf*=2; if(digitalRead(pinNumber)==1) //1 { databuf++; } } for(i=0;i<8;i++) { while(digitalRead(pinNumber)); //data clock start while(!digitalRead(pinNumber)); //data start delayMicroseconds(HIGH_TIME); crc*=2; if(digitalRead(pinNumber)==1) //1 { crc++; } } return 1; } else { return 0; } } int main (void) { printf(“Use GPIO1 to read data!\n”); if (-1 == wiringPiSetup()) { printf(“Setup wiringPi failed!”); return 1; } pinMode(pinNumber, OUTPUT); // set mode to output digitalWrite(pinNumber, 1); // output a high level printf(“Enter OS——-\n”); int i; for(i = 0; i < 2; i++) { pinMode(pinNumber,OUTPUT); // set mode to output digitalWrite(pinNumber, 1); // output a high level delay(1000); if(readSensorData()) { printf(“Congratulations ! Sensor data read ok!\n”); printf(“RH:%d.%d\n”,(databuf>>24)&0xff,(databuf>>16)&0xff); printf(“TMP:%d.%d\n”,(databuf>>8)&0xff,databuf&0xff); databuf=0; } else { printf(“Sorry! Sensor dosent ans!\n”); databuf=0; } } return 0; } |
因为DHT11相当之不靠谱，所以可以看见获取温度的时候重复了两次，尽量保证能够拿到数据。编译的时候需要注意一些额外的参数
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gcc -o dht11 dht11.c -lwiringPi -lpthread -lm |
运行一下应该可以看到这样的内容（第一次失败了吧，我就说这货不靠谱）
2. 获取温度、湿度数据并在LCD上显示
因为DHT是用C驱动的，而LCD我又是用python驱动的，所以只能辛苦python一下，让它从C程序的输出中找到温度和湿度了。
建立一个lcd_clock.py，并贴入以下内容
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#!/usr/bin/python # # based on code from lrvick and LiquidCrystal # lrvic – https://github.com/lrvick/raspi-hd44780/blob/master/hd44780.py # LiquidCrystal – https://github.com/arduino/Arduino/blob/master/libraries/LiquidCrystal/LiquidCrystal.cpp # import subprocess import re import sys from time import sleep from datetime import datetime class Adafruit_CharLCD: # 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 # 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 def __init__(self, pin_rs=14, pin_e=15, pins_db=[17, 18, 27, 22], GPIO = None): # Emulate the old behavior of using RPi.GPIO if we haven’t been given # an explicit GPIO interface to use if not GPIO: import RPi.GPIO as GPIO self.GPIO = GPIO self.pin_rs = pin_rs self.pin_e = pin_e self.pins_db = pins_db self.GPIO.setmode(GPIO.BCM) self.GPIO.setup(self.pin_e, GPIO.OUT) self.GPIO.setup(self.pin_rs, GPIO.OUT) for pin in self.pins_db: self.GPIO.setup(pin, GPIO.OUT) self.write4bits(0x33) # initialization self.write4bits(0x32) # initialization self.write4bits(0x28) # 2 line 5×7 matrix self.write4bits(0x0C) # turn cursor off 0x0E to enable cursor self.write4bits(0x06) # shift cursor right self.displaycontrol = self.LCD_DISPLAYON | self.LCD_CURSOROFF | self.LCD_BLINKOFF self.displayfunction = self.LCD_4BITMODE | self.LCD_1LINE | self.LCD_5x8DOTS self.displayfunction |= self.LCD_2LINE “”” Initialize to default text direction (for romance languages) “”” self.displaymode = self.LCD_ENTRYLEFT | self.LCD_ENTRYSHIFTDECREMENT self.write4bits(self.LCD_ENTRYMODESET | self.displaymode) # set the entry mode self.clear() def begin(self, cols, lines): if (lines > 1): self.numlines = lines self.displayfunction |= self.LCD_2LINE self.currline = 0 def home(self): self.write4bits(self.LCD_RETURNHOME) # set cursor position to zero self.delayMicroseconds(3000) # this command takes a long time! def clear(self): self.write4bits(self.LCD_CLEARDISPLAY) # command to clear display self.delayMicroseconds(3000) # 3000 microsecond sleep, clearing the display takes a long time def setCursor(self, col, row): self.row_offsets = [ 0x00, 0x40, 0x14, 0x54 ] if ( row > self.numlines ): row = self.numlines – 1 # we count rows starting w/0 self.write4bits(self.LCD_SETDDRAMADDR | (col + self.row_offsets[row])) def noDisplay(self): “”” Turn the display off (quickly) “”” self.displaycontrol &= ~self.LCD_DISPLAYON self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol) def display(self): “”” Turn the display on (quickly) “”” self.displaycontrol |= self.LCD_DISPLAYON self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol) def noCursor(self): “”” Turns the underline cursor on/off “”” self.displaycontrol &= ~self.LCD_CURSORON self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol) def cursor(self): “”” Cursor On “”” self.displaycontrol |= self.LCD_CURSORON self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol) def noBlink(self): “”” Turn on and off the blinking cursor “”” self.displaycontrol &= ~self.LCD_BLINKON self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol) def noBlink(self): “”” Turn on and off the blinking cursor “”” self.displaycontrol &= ~self.LCD_BLINKON self.write4bits(self.LCD_DISPLAYCONTROL | self.displaycontrol) def DisplayLeft(self): “”” These commands scroll the display without changing the RAM “”” self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVELEFT) def scrollDisplayRight(self): “”” These commands scroll the display without changing the RAM “”” self.write4bits(self.LCD_CURSORSHIFT | self.LCD_DISPLAYMOVE | self.LCD_MOVERIGHT); def leftToRight(self): “”” This is for text that flows Left to Right “”” self.displaymode |= self.LCD_ENTRYLEFT self.write4bits(self.LCD_ENTRYMODESET | self.displaymode); def rightToLeft(self): “”” This is for text that flows Right to Left “”” self.displaymode &= ~self.LCD_ENTRYLEFT self.write4bits(self.LCD_ENTRYMODESET | self.displaymode) def autoscroll(self): “”” This will ‘right justify’ text from the cursor “”” self.displaymode |= self.LCD_ENTRYSHIFTINCREMENT self.write4bits(self.LCD_ENTRYMODESET | self.displaymode) def noAutoscroll(self): “”” This will ‘left justify’ text from the cursor “”” self.displaymode &= ~self.LCD_ENTRYSHIFTINCREMENT self.write4bits(self.LCD_ENTRYMODESET | self.displaymode) def write4bits(self, bits, char_mode=False): “”” Send command to LCD “”” self.delayMicroseconds(1000) # 1000 microsecond sleep bits=bin(bits)[2:].zfill(8) self.GPIO.output(self.pin_rs, char_mode) for pin in self.pins_db: self.GPIO.output(pin, False) for i in range(4): if bits[i] == “1”: self.GPIO.output(self.pins_db[::-1][i], True) self.pulseEnable() for pin in self.pins_db: self.GPIO.output(pin, False) for i in range(4,8): if bits[i] == “1”: self.GPIO.output(self.pins_db[::-1][i-4], True) self.pulseEnable() def delayMicroseconds(self, microseconds): seconds = microseconds / float(1000000) # divide microseconds by 1 million for seconds sleep(seconds) def pulseEnable(self): self.GPIO.output(self.pin_e, False) self.delayMicroseconds(1) # 1 microsecond pause – enable pulse must be > 450ns self.GPIO.output(self.pin_e, True) self.delayMicroseconds(1) # 1 microsecond pause – enable pulse must be > 450ns self.GPIO.output(self.pin_e, False) self.delayMicroseconds(1) # commands need > 37us to settle def message(self, text): “”” Send string to LCD. Newline wraps to second line””” for char in text: if char == ‘\n’: self.write4bits(0xC0) # next line else: self.write4bits(ord(char),True) if __name__ == ‘__main__’: lcd = Adafruit_CharLCD() lcd.noBlink() while True: sleep(1) output = subprocess.check_output([“./dht11”]); #print output matches = re.search(“TMP:([0-9.]+)”,output) if (not matches): sleep(1) continue temp = float(matches.group(1)) #print temp matches = re.search(“RH:([0-9.]+)”, output) if (not matches): sleep(1) continue humidity = float(matches.group(1)) #print humidity lcd.clear() lcd.message(‘TMP:%s’ % ( temp )) lcd.message(‘ HM:%s’ % ( humidity )) lcd.message(datetime.now().strftime(‘\n%Y-%m-%d %H:%M:%S’)) |
保存并sudo执行
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sudo python lcd_clock.py #需要后台运行就加个&，然后你就有了一只钟…… |
运行效果是这样的：
这个实验如果在做过LCD和温度传感器的基础上做其实还是相当简单的。因为除了驱动DHT11的C程序之外，最后的lcd_clock.py和上次最后列出的那个python脚本相比，差别只是在于最后的lcdmessage里面多了一个re.search然后调整了一下输出的内容和格式。不过这次倒是确实真的学到了知识，python用来抓输出真是太方便了～然后我现在就有了一只相当好用的温度计+钟……
Acknowledgement
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