树莓派结合ADC做个光敏感应灯

前言

其实没有什么想法，就是想把ADC用熟练了，这些小案例都是自己杜撰的，实际上没有那么多场景需要用，但是最近真的用在了智能浇花设备上，土壤湿度采样的传感器是模拟的，所以，可以用ADC秀一波操作。

操作步骤

• 步骤1：从https://www.raspberrypi.org/downloads/下载最新镜像，然后选择Raspbian。
• 步骤2：烧录镜像然后启动树莓派。 
• 步骤3：通过在终端中键入以下命令连接到Internet并更新系统：

  sudo apt-get update
  sudo apt-get upgrade

• 步骤4：将所有东西连接在一起然后打开你的树莓派，不知道为啥网上给树莓派起名字叫覆盆子，太tm难听了。raspberry就改成树莓不行么？
  

  手绘电路图，看懂了就过，看不懂就自己学习一下再过。

  

  接驳示意图，ADC的AIN1 通道采样。中间抽头给树莓派，采集信号信息。

  C语言编程

  下面的内容就是开始编程了，如果你喜欢用C，那么就这样，写个源码:

  #include <stdio.h>
  #include <stdlib.h>
  #include <linux/i2c-dev.h>
  #include <sys/ioctl.h>
  #include <fcntl.h>
  #include <wiringPi.h>
  void main()
  {
  wiringPiSetup(); 
  //Physical Pin = 40, name is GPIO.29 and wPi name is 29, BCM 21.
  pinMode(29, OUTPUT);   
  int file; 
  char *bus = "/dev/i2c-1";
  if ((file = open(bus, O_RDWR)) < 0) 
  {
   printf("Failed to open the bus.\n");
   exit(1);
   } 
  // Get I2C device, ADS1115 I2C address is 0x48(72)
  ioctl(file, I2C_SLAVE, 0x48) 
  // Select configuration register(0x01)
  // AINP = AIN0 and AINN = AIN1, +/- 2.048V 
  // Continuous conversion mode, 128 SPS(0x84, 0x83) 
  char config[3] = {0}; 
  config[0] = 0x01; 
  config[1] = 0xD4; 
  config[2] = 0x83; 
  write(file, config, 3); 
  sleep(1); 
  // Read 2 bytes of data from register(0x00) 
  // raw_adc msb, raw_adc lsb 
  char reg[1] = {0x00};
  write(file, reg, 1); 
  char data[2]={0};
  if(read(file, data, 2) != 2) 
  { 
  printf("Error : Input/Output Error\n");
  }
  else
  { 
  // Convert the data 
  int raw_adc = (data[0] * 256 + data[1]);
  if (raw_adc > 32767) 
  { 
    raw_adc -= 65535; 
  }
  // Output data to screen 
  printf("Analog Data is: %d \n", raw_adc);
  if ( raw_adc > 3200 )
   { 
    printf("Turn on LED\n");
    digitalWrite(29, LOW); // turn on the LED 
    } 
  else { 
      printf("Turn off LED\n"); 
      digitalWrite(29, HIGH);  //turn off the LED
        }
   } 
  }

  编译和测试：

  gcc -o adc -lwiringPi adc.c 

  注意：

• gcc是编译工具，-o表示定义输出文件名，-lwiringPi表示需要使用wiringPi的库来完成编译代码。
• 编译后，将在工作目录中获得名为sensor的二进制文件,只需使用此命令执行它：

  while true
  do
  ./adc 
  done

  

Python编程

• 如果你喜欢用python好吧，那么就更简单了。直接用adafruit的ads1x15的代码改改就能用。

  #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  # Author: Jacky.Li
  # License: Public Domain
  import time
  import Adafruit_ADS1x15
  import os
  adc = Adafruit_ADS1x15.ADS1115()
  # Choose a gain of 1 for reading voltages from 0 to 4.09V.
  # Or pick a different gain to change the range of voltages that are read:
  # - 2/3 = +/-6.144V
  # - 1 = +/-4.096V
  # - 2 = +/-2.048V
  # - 4 = +/-1.024V
  # - 8 = +/-0.512V
  # - 16 = +/-0.256V
  # See table 3 in the ADS1015/ADS1115 datasheet for more info on gain.
  GAIN = 1
  print("Reading ADS1115 values, press Ctrl-C to quit...") 
  # Main loop. 
  while True:
  # Read all the ADC channel values in a list.
  values = [0]*4
  for i in range(4):
  # Read the specified ADC channel using the previously set gain value.
  values[i] = adc.read_adc(i, gain=GAIN) 
  # Note you can also pass in an optional data_rate parameter that controls 
  # the ADC conversion time (in samples/second). Each chip has a different 
  # set of allowed data rate values, see datasheet Table 9 config register 
  # DR bit values. 
  #values[i] = adc.read_adc(i, gain=GAIN, data_rate=128) 
  # Each value will be a 12 or 16 bit signed integer value depending on the   
  # ADC (ADS1015 = 12-bit, ADS1115 = 16-bit). 
  # Print the ADC values. 
  print(values[1]) 
  # print analog data which detected via ADC AIN1 port.
  if values[1] < 3000: 
      os.system("gpio mode 29 out")
      os.system("gpio write 29 1") 
  else: 
      os.system("gpio mode 29 in") 
  os.system("gpio write 29 0") 
  time.sleep(0.25)</span>

  运行看看效果

  python sensor.py

  嗯，就这样吧，开开脑洞就可以玩儿得更愉快。。哈哈， 白了个白~