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~

标签：ADS115

树莓派结合ADC做个光敏感应的灯