ads1115与树莓派

Raspberry Pi 读取模拟信号

急需求解:

使用Raspberry Pi读取输出模拟信号

由于Raspberry Pi 3B内部没有集成ADC，因此需要外接 ADC 来进行模数转换。外接 ADC 选用的是 ADS1115， I2C 的通讯方式实现起来相对容易些。

简单介绍一下ADS模拟-数字转换器

特点：

1）超小型QFN封装：2mm1.5mm0.4mm
2）宽电源电压范围：2.0V-5.5V
3）低消耗电流：连续模式：只有150u单次模式，自动关闭
4）可编成数据速率：8SPS到860SPS
5）内部底漂移电压基准
6）内部振荡器
7）内部PGA
8）I2C接口：引脚可选择的地址
9）四个单端或两个差分输入（ADS1115）
10）可编成比较器（ADS1114和ADS1115）
11）工作温度：-40摄氏度到+140摄氏度

应用

引脚与地址访问

根据ADDR引脚连接不到不同的引脚上，其I2C的访问地址是不同的：

• 当ADDR引脚连接到GND时，地址为：0x48（0100, 1000B）
• 当ADDR引脚连接到VDD时，地址为：0x49（0100, 1001B）
• 当ADDR引脚连接到SDA时，地址为：0x4A（0100, 1010B）
• 当ADDR引脚连接到SCL时，地址为：0x4B（0100, 1011B）

根据以上可以得到，我们一个I2C接口单层级联，可以同时连接4个ADS1115,也就是单层一个I2C接口可以同时测量16路16位的模拟电压量。

接线

VDD – 5V

GND – GND

SCL – SCL

SDA – SDA

ADDR – GND

A0 – MQ 传感器的 A0

树莓派IIC接口配置

6.检查I2C设备是否在线

sudo apt-get install i2c-tools sudo i2cdetect -y 1 

贴上代码实现功能

ads1115.c

#include  
     #include  
     #include "ads1115.h" /* ADS1115 analogRead function *===================================*/ static int myAnalogRead(struct wiringPiNodeStruct *node, int pin) { 
    int chan = pin - node->pinBase; int data[2]; int value; // Start with default values int config = ADS1015_REG_CONFIG_CQUE_NONE | // Disable the comparator (default val) ADS1015_REG_CONFIG_CLAT_NONLAT | // Non-latching (default val) ADS1015_REG_CONFIG_CPOL_ACTVLOW | // Alert/Rdy active low (default val) ADS1015_REG_CONFIG_CMODE_TRAD | // Traditional comparator (default val) ADS1115_REG_CONFIG_DR_860SPS | // 860 samples per second (max) ADS1015_REG_CONFIG_MODE_SINGLE; // Single-shot mode (default) //ADS1015_REG_CONFIG_MODE_CONTIN; // Continuous mode (doesn't work with more than one channel) // Set PGA/voltage range config |= ADS1015_REG_CONFIG_PGA_4_096V; // Set single-ended input chan switch (chan) { 
    case (0): config |= ADS1015_REG_CONFIG_MUX_SINGLE_0; break; case (1): config |= ADS1015_REG_CONFIG_MUX_SINGLE_1; break; case (2): config |= ADS1015_REG_CONFIG_MUX_SINGLE_2; break; case (3): config |= ADS1015_REG_CONFIG_MUX_SINGLE_3; break; } // Set 'start single-conversion' bit config |= ADS1015_REG_CONFIG_OS_SINGLE; // Sent the config data in the right order config = ((config >> 8) & 0x00FF) | ((config << 8) & 0xFF00); wiringPiI2CWriteReg16(node->fd, ADS1015_REG_POINTER_CONFIG, config); // Wait for conversion to complete delay(2); // (1/SPS rounded up) wiringPiI2CWrite(node->fd, ADS1015_REG_POINTER_CONVERT); data[0] = wiringPiI2CRead(node->fd); data[1] = wiringPiI2CRead(node->fd); value = ((data[0] << 8) & 0xFF00) | data[1]; // wiringPi doesn't include stdint so everything is an int (int32), this should account for this if (value > 0x7FFF) { 
    return (value - 0xFFFF); } else { 
    return value; } } /* ADS1115 ADC setup: * create ADS1115 device. * id is the address of the chip (0x48 default) *===============================================*/ int ads1115Setup(const int pinBase, int id) { 
    struct wiringPiNodeStruct *node; node = wiringPiNewNode(pinBase,4); node->fd = wiringPiI2CSetup(id); node->analogRead = myAnalogRead; if (node->fd < 0) { 
    return -1; } else { 
    return 0; } } 

ads1115.h

/*========================================================================= I2C ADDRESS/BITS -----------------------------------------------------------------------*/ #define ADS1015_ADDRESS (0x48) // 1001 000 (ADDR = GND) /*=========================================================================*/ /*========================================================================= CONVERSION DELAY (in mS) -----------------------------------------------------------------------*/ #define ADS1015_CONVERSIONDELAY (1) #define ADS1115_CONVERSIONDELAY (8) /*=========================================================================*/ /*========================================================================= POINTER REGISTER -----------------------------------------------------------------------*/ #define ADS1015_REG_POINTER_MASK (0x03) #define ADS1015_REG_POINTER_CONVERT (0x00) #define ADS1015_REG_POINTER_CONFIG (0x01) #define ADS1015_REG_POINTER_LOWTHRESH (0x02) #define ADS1015_REG_POINTER_HITHRESH (0x03) /*=========================================================================*/ /*========================================================================= CONFIG REGISTER -----------------------------------------------------------------------*/ #define ADS1015_REG_CONFIG_OS_MASK (0x8000) #define ADS1015_REG_CONFIG_OS_SINGLE (0x8000) // Write: Set to start a single-conversion #define ADS1015_REG_CONFIG_OS_BUSY (0x0000) // Read: Bit = 0 when conversion is in progress #define ADS1015_REG_CONFIG_OS_NOTBUSY (0x8000) // Read: Bit = 1 when device is not performing a conversion #define ADS1015_REG_CONFIG_MUX_MASK (0x7000) #define ADS1015_REG_CONFIG_MUX_DIFF_0_1 (0x0000) // Differential P = AIN0, N = AIN1 (default) #define ADS1015_REG_CONFIG_MUX_DIFF_0_3 (0x1000) // Differential P = AIN0, N = AIN3 #define ADS1015_REG_CONFIG_MUX_DIFF_1_3 (0x2000) // Differential P = AIN1, N = AIN3 #define ADS1015_REG_CONFIG_MUX_DIFF_2_3 (0x3000) // Differential P = AIN2, N = AIN3 #define ADS1015_REG_CONFIG_MUX_SINGLE_0 (0x4000) // Single-ended AIN0 #define ADS1015_REG_CONFIG_MUX_SINGLE_1 (0x5000) // Single-ended AIN1 #define ADS1015_REG_CONFIG_MUX_SINGLE_2 (0x6000) // Single-ended AIN2 #define ADS1015_REG_CONFIG_MUX_SINGLE_3 (0x7000) // Single-ended AIN3 #define ADS1015_REG_CONFIG_PGA_MASK (0x0E00) #define ADS1015_REG_CONFIG_PGA_6_144V (0x0000) // +/-6.144V range = Gain 2/3 #define ADS1015_REG_CONFIG_PGA_4_096V (0x0200) // +/-4.096V range = Gain 1 #define ADS1015_REG_CONFIG_PGA_2_048V (0x0400) // +/-2.048V range = Gain 2 (default) #define ADS1015_REG_CONFIG_PGA_1_024V (0x0600) // +/-1.024V range = Gain 4 #define ADS1015_REG_CONFIG_PGA_0_512V (0x0800) // +/-0.512V range = Gain 8 #define ADS1015_REG_CONFIG_PGA_0_256V (0x0A00) // +/-0.256V range = Gain 16 #define ADS1015_REG_CONFIG_MODE_MASK (0x0100) #define ADS1015_REG_CONFIG_MODE_CONTIN (0x0000) // Continuous conversion mode #define ADS1015_REG_CONFIG_MODE_SINGLE (0x0100) // Power-down single-shot mode (default) #define ADS1015_REG_CONFIG_DR_MASK (0x00E0)  #define ADS1015_REG_CONFIG_DR_128SPS (0x0000) // 128 samples per second #define ADS1015_REG_CONFIG_DR_250SPS (0x0020) // 250 samples per second #define ADS1015_REG_CONFIG_DR_490SPS (0x0040) // 490 samples per second #define ADS1015_REG_CONFIG_DR_920SPS (0x0060) // 920 samples per second #define ADS1015_REG_CONFIG_DR_1600SPS (0x0080) // 1600 samples per second (default) #define ADS1015_REG_CONFIG_DR_2400SPS (0x00A0) // 2400 samples per second #define ADS1015_REG_CONFIG_DR_3300SPS (0x00C0) // 3300 samples per second #define ADS1115_REG_CONFIG_DR_8SPS ( 0x0000 ) // 8 samples per second #define ADS1115_REG_CONFIG_DR_16SPS ( 0x0020 ) // 16 samples per second #define ADS1115_REG_CONFIG_DR_32SPS ( 0x0040 ) // 32 samples per second #define ADS1115_REG_CONFIG_DR_64SPS ( 0x0060 ) // 64 samples per second #define ADS1115_REG_CONFIG_DR_128SPS ( 0x0080 ) // 128 samples per second #define ADS1115_REG_CONFIG_DR_250SPS ( 0x00A0 ) // 250 samples per second (default) #define ADS1115_REG_CONFIG_DR_475SPS ( 0x00C0 ) // 475 samples per second #define ADS1115_REG_CONFIG_DR_860SPS ( 0x00E0 ) // 860 samples per second #define ADS1015_REG_CONFIG_CMODE_MASK (0x0010) #define ADS1015_REG_CONFIG_CMODE_TRAD (0x0000) // Traditional comparator with hysteresis (default) #define ADS1015_REG_CONFIG_CMODE_WINDOW (0x0010) // Window comparator #define ADS1015_REG_CONFIG_CPOL_MASK (0x0008) #define ADS1015_REG_CONFIG_CPOL_ACTVLOW (0x0000) // ALERT/RDY pin is low when active (default) #define ADS1015_REG_CONFIG_CPOL_ACTVHI (0x0008) // ALERT/RDY pin is high when active #define ADS1015_REG_CONFIG_CLAT_MASK (0x0004) // Determines if ALERT/RDY pin latches once asserted #define ADS1015_REG_CONFIG_CLAT_NONLAT (0x0000) // Non-latching comparator (default) #define ADS1015_REG_CONFIG_CLAT_LATCH (0x0004) // Latching comparator #define ADS1015_REG_CONFIG_CQUE_MASK (0x0003) #define ADS1015_REG_CONFIG_CQUE_1CONV (0x0000) // Assert ALERT/RDY after one conversions #define ADS1015_REG_CONFIG_CQUE_2CONV (0x0001) // Assert ALERT/RDY after two conversions #define ADS1015_REG_CONFIG_CQUE_4CONV (0x0002) // Assert ALERT/RDY after four conversions #define ADS1015_REG_CONFIG_CQUE_NONE (0x0003) // Disable the comparator and put ALERT/RDY in high state (default) /*=========================================================================*/ #ifdef __cplusplus extern "c" { 
    #endif extern int ads1115Setup(int pinBase, int id); #ifdef __cplusplus } #endif 

ads1115_read.c

#include  
     #include  
     #include  
     #include  
     int main(int argc, char *argv[]) { 
    int16_t value; double voltage; ads1115Setup(100,0x48); for (;;) { 
    value = (int16_t) analogRead(100); voltage = value * (4.096 / 32768); printf("ADS1115 Reading: %d\n\r",value); printf("ADS1115 Voltage: %g\n\r",voltage); delay(1000); } return 0; } 

执行gcc ads1115.c ads1115.h ads1115_read.c -lwiringPi -o ads运行程序
执行./ads出现结果

完成！！！