使用Arduino驅動 ADS1115 ADC采樣芯片

如圖，這是這顆ADC采樣芯片的內部結構圖，可以看到， 從芯片引腳到芯片內部的ADC模塊，還有幾個部分： MUX，PGA， 這兩個分別叫做多路復用器、和增益放大器， MUX用來切換采樣引腳，而PGA則用來切換測量量程。

我參照芯片官方的數據手冊寫出了這個簡易的測試程序，只用到了最基本的IIC的通訊， 使用功能也比較有限，高級一些的功能都需要使用基於IIC通訊的SMBUS協議， 這個就沒有繼續深究了。

#include <Wire.h>

const int8_t ADS1115_address = 0x48;



enum ADS1115Conf{
  AIN0_2AIN1  =  0b000, // << 12,
  AIN0_2AIN3  =  0b001, // << 12,
  AIN1_2AIN3  =  0b010, // << 12,
  AIN2_2AIN3  =  0b011, // << 12,
  AIN0_2GND   =  0b100, // << 12,
  AIN1_2GND   =  0b101, // << 12,
  AIN2_2GND   =  0b110, // << 12,
  AIN3_2GND   =  0b111, // << 12,

  FSR_6_144V  =  0b000, // << 9,
  FSR_4_096V  =  0b001, // << 9,
  FSR_2_048V  =  0b010, // << 9,
  FSR_1_024V  =  0b011, // << 9,
  FSR_0_512V  =  0b100, // << 9,
  FSR_0_256V  =  0b101, // << 9,

  CONTINU_CONV = 0, //<<8
  SINGLE_SHOT =  1,

  SPS_8       =  0b000, // << 5,
  SPS_16      =  0b001, // << 5,
  SPS_32      =  0b010, // << 5,
  SPS_64      =  0b011, // << 5,
  SPS_128     =  0b100, // << 5,
  SPS_250     =  0b101, // << 5,
  SPS_475     =  0b110, // << 5,
  SPS_860     =  0b111, // << 5,

}typedef ADS1115Conf;

/**
 * [ADS1115Configure description]
 * @Author     葉鵬程
 * @DateTime   2019-08-19T20:44:30+0800
 * @discrption : 芯片初始化配置
 *  
 * @param      mux                      [輸入通道配置]
 * @param      pga                      [量程設置]
 * @param      mode                     [單次或持續轉換模式]
 * @param      dr                       [采樣速率設置]
 */
void ADS1115Configure(ADS1115Conf mux, ADS1115Conf pga, ADS1115Conf mode, ADS1115Conf dr){

  uint16_t conf;

  Wire.beginTransmission(ADS1115_address);
  Wire.write(0x01);  //set Address Pointer Register as conf Register
  Wire.endTransmission();

  /*read chip's conf register data */
  Wire.requestFrom(ADS1115_address, 2);
  conf = 0;
  conf = Wire.read();
  conf = conf<<8;
  conf |= Wire.read();

  /*change it*/
  conf = 0x8000;
  conf &= (~(0x0007<< 12)); conf |= mux   << 12;
  conf &= (~(0x0007<< 9 )); conf |= pga   << 9;
  conf &= (~(0x0007<< 8 )); conf |= mode  << 8;
  conf &= (~(0x0007<< 5 )); conf |= dr    << 5;

  // conf = 0xf483;
  /* trans back*/
   Wire.beginTransmission(ADS1115_address);
   Wire.write(0x01);  //set Address Pointer Register as conf Register
   Wire.write(uint8_t(conf>>8));  //conf MSB
   Wire.write(uint8_t(conf));  //conf LSB
   Wire.endTransmission();

    /**/
  Wire.beginTransmission(ADS1115_address);
  Wire.write(0x00);  //set Address Pointer Register as conf Register
  Wire.endTransmission();
}

/**
 * [ADS1115SetChannel description]
 * @Author     葉鵬程
 * @DateTime   2019-08-19T20:43:57+0800
 * @discrption :芯片輸入通道設置
 *  
 * @param      mux                      [description]
 */
void ADS1115SetChannel(ADS1115Conf mux){

  uint16_t conf;

  Wire.beginTransmission(ADS1115_address);
  Wire.write(0x01);  //set Address Pointer Register as conf Register
  Wire.endTransmission();

  /*read chip's conf register data */
  Wire.requestFrom(ADS1115_address, 2);
  conf = 0;
  conf = Wire.read();
  conf = conf<<8;
  conf |= Wire.read();

  /*change it*/
  conf = conf & (~(0x0007<< 12)); conf |= mux << 12;
  

  /* trans back*/
  Wire.beginTransmission(ADS1115_address);
  Wire.write(0x01);  //set Address Pointer Register as conf Register
  Wire.write(uint8_t(conf>>8));  //conf MSB
  Wire.write(uint8_t(conf));  //conf LSB
  Wire.endTransmission();

   /**/
  Wire.beginTransmission(ADS1115_address);
  Wire.write(0x00);  //set Address Pointer Register as conf Register
  Wire.endTransmission();
}

int16_t ADS1115ReadResult(void){
  int16_t ret;

  Wire.requestFrom(ADS1115_address, 2);
  ret = 0;
  ret = Wire.read();
  ret = ret<<8;
  ret |= Wire.read();

  return ret;
}

void setup() {
  // put your setup code here, to run once:
  Wire.begin();
 
  Serial.begin(115200);
  while (!Serial);             // Leonardo: wait for serial monitor
  Serial.println("Arduino Running!");
  Serial.println("configing ADS1115.");
  delay(200);
  ADS1115Configure(AIN3_2GND, FSR_6_144V, CONTINU_CONV, SPS_250);
  Serial.println("configed."); 
  
  Wire.beginTransmission(ADS1115_address);
   Wire.write(0x00);  //set Address Pointer Register as conv Register
   Wire.write(0x00);  
   Wire.write(0x00);
   Wire.endTransmission();
}

void loop() {
  int16_t adc_result;
  double v;
  Serial.print("adc conversion result: ");
  
  ADS1115SetChannel(AIN0_2GND);
  delay(10);
  adc_result = ADS1115ReadResult(); v = adc_result * 6.144 / 0x7fff;
  Serial.print("\tA0: "); Serial.print(v); Serial.print('V');
  
  ADS1115SetChannel(AIN1_2GND);
  delay(10);
  adc_result = ADS1115ReadResult(); v = adc_result * 6.144 / 0x7fff;
  Serial.print("\tA1: "); Serial.print(v); Serial.print('V'); 

  ADS1115SetChannel(AIN2_2GND);
  delay(10);
  adc_result = ADS1115ReadResult(); v = adc_result * 6.144 / 0x7fff;
  Serial.print("\tA2: "); Serial.print(v); Serial.print('V'); 
  
  ADS1115SetChannel(AIN3_2GND);
  delay(10);
  adc_result = ADS1115ReadResult(); v = adc_result * 6.144 / 0x7fff;
  Serial.print("\tA3: "); Serial.print(v); Serial.print('V'); 

  Serial.println();
  delay(100);
  // put your main code here, to run repeatedly:

}