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关于INA219AID检测电流电压问题

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独孤垂钓2003|  楼主 | 2014-12-10 20:11 | 只看该作者 回帖奖励 |倒序浏览 |阅读模式
请问用过TI的INA219AID芯片的兄弟:偶用该芯片来检测开关电源输出的电流和电压,高侧检流。根据INA219的Datasheet,如果只需要读取采样电阻的Shunt Voltage和Bus Voltage不需要任何配置即可。

现在我碰到几个问题,调了几天了还是没有头绪:
1、根据Datasheet的说的输出寄存器格式读取Shunt Voltage和Bus Voltage结果都不对,其中如果把Shunt Voltage寄存器的数值除以2,结果相对接近些,但误差还是很大。而Bus Voltage按照datasheet格式,右移三位的结果是实际电压的两倍,也就是说如果右移四位的结果比较接近实际输出。

2、如果将Shunt Voltage寄存器的值按照除以2作为实际输出结果,发现几十mA的电流检测不出来,直接从0mA跳到20几mA去了。

INA219AID的芯片都换N多,包括直接从TI代理买了一批,美国直接进口的,还是一样的结果。

I2C总线的驱动也换了几个,结果都一样。 MCU用的是STC的15F系列,应该跟它没有什么关系。

请有经验的兄弟帮帮忙,看看可能什么地方没有注意到。

另外,硬件连接用的datasheet的参考设计,差分输入部分有RC滤波,但去掉结果还是一样。

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沙发
独孤垂钓2003|  楼主 | 2014-12-10 20:16 | 只看该作者
代码参考的这一份,I2C部分替换掉。

/**************************************************************************/
/*!
    @file     Adafruit_INA219.cpp
    @author   K.Townsend (Adafruit Industries)
        @license  BSD (see license.txt)
        
        Driver for the INA219 current sensor

        This is a library for the Adafruit INA219 breakout
        
               
        Adafruit invests time and resources providing this open source code,
        please support Adafruit and open-source hardware by purchasing
        products from Adafruit!

        @section  HISTORY

    v1.0 - First release
*/
/**************************************************************************/
#if ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif

#include <Wire.h>

#include "Adafruit_INA219.h"

/**************************************************************************/
/*!
    @brief  Sends a single command byte over I2C
*/
/**************************************************************************/
void Adafruit_INA219::wireWriteRegister (uint8_t reg, uint16_t value)
{
  Wire.beginTransmission(ina219_i2caddr);
  #if ARDUINO >= 100
    Wire.write(reg);                       // Register
    Wire.write((value >> 8) & 0xFF);       // Upper 8-bits
    Wire.write(value & 0xFF);              // Lower 8-bits
  #else
    Wire.send(reg);                        // Register
    Wire.send(value >> 8);                 // Upper 8-bits
    Wire.send(value & 0xFF);               // Lower 8-bits
  #endif
  Wire.endTransmission();
}

/**************************************************************************/
/*!
    @brief  Reads a 16 bit values over I2C
*/
/**************************************************************************/
void Adafruit_INA219::wireReadRegister(uint8_t reg, uint16_t *value)
{

  Wire.beginTransmission(ina219_i2caddr);
  #if ARDUINO >= 100
    Wire.write(reg);                       // Register
  #else
    Wire.send(reg);                        // Register
  #endif
  Wire.endTransmission();
  
  delay(1); // Max 12-bit conversion time is 586us per sample

  Wire.requestFrom(ina219_i2caddr, (uint8_t)2);  
  #if ARDUINO >= 100
    // Shift values to create properly formed integer
    *value = ((Wire.read() << 8) | Wire.read());
  #else
    // Shift values to create properly formed integer
    *value = ((Wire.receive() << 8) | Wire.receive());
  #endif
}

/**************************************************************************/
/*!
    @brief  Configures to INA219 to be able to measure up to 32V and 2A
            of current.  Each unit of current corresponds to 100uA, and
            each unit of power corresponds to 2mW. Counter overflow
            occurs at 3.2A.
                        
    @NOTE   These calculations assume a 0.1 ohm resistor is present
*/
/**************************************************************************/
void Adafruit_INA219::ina219SetCalibration_32V_2A(void)
{
  // By default we use a pretty huge range for the input voltage,
  // which probably isn't the most appropriate choice for system
  // that don't use a lot of power.  But all of the calculations
  // are shown below if you want to change the settings.  You will
  // also need to change any relevant register settings, such as
  // setting the VBUS_MAX to 16V instead of 32V, etc.

  // VBUS_MAX = 32V             (Assumes 32V, can also be set to 16V)
  // VSHUNT_MAX = 0.32          (Assumes Gain 8, 320mV, can also be 0.16, 0.08, 0.04)
  // RSHUNT = 0.1               (Resistor value in ohms)
  
  // 1. Determine max possible current
  // MaxPossible_I = VSHUNT_MAX / RSHUNT
  // MaxPossible_I = 3.2A
  
  // 2. Determine max expected current
  // MaxExpected_I = 2.0A
  
  // 3. Calculate possible range of LSBs (Min = 15-bit, Max = 12-bit)
  // MinimumLSB = MaxExpected_I/32767
  // MinimumLSB = 0.000061              (61uA per bit)
  // MaximumLSB = MaxExpected_I/4096
  // MaximumLSB = 0,000488              (488uA per bit)
  
  // 4. Choose an LSB between the min and max values
  //    (Preferrably a roundish number close to MinLSB)
  // CurrentLSB = 0.0001 (100uA per bit)
  
  // 5. Compute the calibration register
  // Cal = trunc (0.04096 / (Current_LSB * RSHUNT))
  // Cal = 4096 (0x1000)
  
  ina219_calValue = 4096;
  
  // 6. Calculate the power LSB
  // PowerLSB = 20 * CurrentLSB
  // PowerLSB = 0.002 (2mW per bit)
  
  // 7. Compute the maximum current and shunt voltage values before overflow
  //
  // Max_Current = Current_LSB * 32767
  // Max_Current = 3.2767A before overflow
  //
  // If Max_Current > Max_Possible_I then
  //    Max_Current_Before_Overflow = MaxPossible_I
  // Else
  //    Max_Current_Before_Overflow = Max_Current
  // End If
  //
  // Max_ShuntVoltage = Max_Current_Before_Overflow * RSHUNT
  // Max_ShuntVoltage = 0.32V
  //
  // If Max_ShuntVoltage >= VSHUNT_MAX
  //    Max_ShuntVoltage_Before_Overflow = VSHUNT_MAX
  // Else
  //    Max_ShuntVoltage_Before_Overflow = Max_ShuntVoltage
  // End If
  
  // 8. Compute the Maximum Power
  // MaximumPower = Max_Current_Before_Overflow * VBUS_MAX
  // MaximumPower = 3.2 * 32V
  // MaximumPower = 102.4W
  
  // Set multipliers to convert raw current/power values
  ina219_currentDivider_mA = 10;  // Current LSB = 100uA per bit (1000/100 = 10)
  ina219_powerDivider_mW = 2;     // Power LSB = 1mW per bit (2/1)

  // Set Calibration register to 'Cal' calculated above        
  wireWriteRegister(INA219_REG_CALIBRATION, ina219_calValue);
  
  // Set Config register to take into account the settings above
  uint16_t config = INA219_CONFIG_BVOLTAGERANGE_32V |
                    INA219_CONFIG_GAIN_8_320MV |
                    INA219_CONFIG_BADCRES_12BIT |
                    INA219_CONFIG_SADCRES_12BIT_1S_532US |
                    INA219_CONFIG_MODE_SANDBVOLT_CONTINUOUS;
  wireWriteRegister(INA219_REG_CONFIG, config);
}

/**************************************************************************/
/*!
    @brief  Configures to INA219 to be able to measure up to 32V and 1A
            of current.  Each unit of current corresponds to 40uA, and each
            unit of power corresponds to 800�W. Counter overflow occurs at
            1.3A.
                        
    @NOTE   These calculations assume a 0.1 ohm resistor is present
*/
/**************************************************************************/
void Adafruit_INA219::ina219SetCalibration_32V_1A(void)
{
  // By default we use a pretty huge range for the input voltage,
  // which probably isn't the most appropriate choice for system
  // that don't use a lot of power.  But all of the calculations
  // are shown below if you want to change the settings.  You will
  // also need to change any relevant register settings, such as
  // setting the VBUS_MAX to 16V instead of 32V, etc.

  // VBUS_MAX = 32V                (Assumes 32V, can also be set to 16V)
  // VSHUNT_MAX = 0.32        (Assumes Gain 8, 320mV, can also be 0.16, 0.08, 0.04)
  // RSHUNT = 0.1                        (Resistor value in ohms)

  // 1. Determine max possible current
  // MaxPossible_I = VSHUNT_MAX / RSHUNT
  // MaxPossible_I = 3.2A

  // 2. Determine max expected current
  // MaxExpected_I = 1.0A

  // 3. Calculate possible range of LSBs (Min = 15-bit, Max = 12-bit)
  // MinimumLSB = MaxExpected_I/32767
  // MinimumLSB = 0.0000305             (30.5�A per bit)
  // MaximumLSB = MaxExpected_I/4096
  // MaximumLSB = 0.000244              (244�A per bit)

  // 4. Choose an LSB between the min and max values
  //    (Preferrably a roundish number close to MinLSB)
  // CurrentLSB = 0.0000400 (40�A per bit)

  // 5. Compute the calibration register
  // Cal = trunc (0.04096 / (Current_LSB * RSHUNT))
  // Cal = 10240 (0x2800)

  ina219_calValue = 10240;
  
  // 6. Calculate the power LSB
  // PowerLSB = 20 * CurrentLSB
  // PowerLSB = 0.0008 (800�W per bit)

  // 7. Compute the maximum current and shunt voltage values before overflow
  //
  // Max_Current = Current_LSB * 32767
  // Max_Current = 1.31068A before overflow
  //
  // If Max_Current > Max_Possible_I then
  //    Max_Current_Before_Overflow = MaxPossible_I
  // Else
  //    Max_Current_Before_Overflow = Max_Current
  // End If
  //
  // ... In this case, we're good though since Max_Current is less than MaxPossible_I
  //
  // Max_ShuntVoltage = Max_Current_Before_Overflow * RSHUNT
  // Max_ShuntVoltage = 0.131068V
  //
  // If Max_ShuntVoltage >= VSHUNT_MAX
  //    Max_ShuntVoltage_Before_Overflow = VSHUNT_MAX
  // Else
  //    Max_ShuntVoltage_Before_Overflow = Max_ShuntVoltage
  // End If

  // 8. Compute the Maximum Power
  // MaximumPower = Max_Current_Before_Overflow * VBUS_MAX
  // MaximumPower = 1.31068 * 32V
  // MaximumPower = 41.94176W

  // Set multipliers to convert raw current/power values
  ina219_currentDivider_mA = 25;      // Current LSB = 40uA per bit (1000/40 = 25)
  ina219_powerDivider_mW = 1;         // Power LSB = 800�W per bit

  // Set Calibration register to 'Cal' calculated above        
  wireWriteRegister(INA219_REG_CALIBRATION, ina219_calValue);

  // Set Config register to take into account the settings above
  uint16_t config = INA219_CONFIG_BVOLTAGERANGE_32V |
                    INA219_CONFIG_GAIN_8_320MV |
                    INA219_CONFIG_BADCRES_12BIT |
                    INA219_CONFIG_SADCRES_12BIT_1S_532US |
                    INA219_CONFIG_MODE_SANDBVOLT_CONTINUOUS;
  wireWriteRegister(INA219_REG_CONFIG, config);
}

void Adafruit_INA219::ina219SetCalibration_16V_400mA(void) {
  
  // Calibration which uses the highest precision for
  // current measurement (0.1mA), at the expense of
  // only supporting 16V at 400mA max.

  // VBUS_MAX = 16V
  // VSHUNT_MAX = 0.04          (Assumes Gain 1, 40mV)
  // RSHUNT = 0.1               (Resistor value in ohms)
  
  // 1. Determine max possible current
  // MaxPossible_I = VSHUNT_MAX / RSHUNT
  // MaxPossible_I = 0.4A

  // 2. Determine max expected current
  // MaxExpected_I = 0.4A
  
  // 3. Calculate possible range of LSBs (Min = 15-bit, Max = 12-bit)
  // MinimumLSB = MaxExpected_I/32767
  // MinimumLSB = 0.0000122              (12uA per bit)
  // MaximumLSB = MaxExpected_I/4096
  // MaximumLSB = 0.0000977              (98uA per bit)
  
  // 4. Choose an LSB between the min and max values
  //    (Preferrably a roundish number close to MinLSB)
  // CurrentLSB = 0.00005 (50uA per bit)
  
  // 5. Compute the calibration register
  // Cal = trunc (0.04096 / (Current_LSB * RSHUNT))
  // Cal = 8192 (0x2000)

  ina219_calValue = 8192;

  // 6. Calculate the power LSB
  // PowerLSB = 20 * CurrentLSB
  // PowerLSB = 0.001 (1mW per bit)
  
  // 7. Compute the maximum current and shunt voltage values before overflow
  //
  // Max_Current = Current_LSB * 32767
  // Max_Current = 1.63835A before overflow
  //
  // If Max_Current > Max_Possible_I then
  //    Max_Current_Before_Overflow = MaxPossible_I
  // Else
  //    Max_Current_Before_Overflow = Max_Current
  // End If
  //
  // Max_Current_Before_Overflow = MaxPossible_I
  // Max_Current_Before_Overflow = 0.4
  //
  // Max_ShuntVoltage = Max_Current_Before_Overflow * RSHUNT
  // Max_ShuntVoltage = 0.04V
  //
  // If Max_ShuntVoltage >= VSHUNT_MAX
  //    Max_ShuntVoltage_Before_Overflow = VSHUNT_MAX
  // Else
  //    Max_ShuntVoltage_Before_Overflow = Max_ShuntVoltage
  // End If
  //
  // Max_ShuntVoltage_Before_Overflow = VSHUNT_MAX
  // Max_ShuntVoltage_Before_Overflow = 0.04V
  
  // 8. Compute the Maximum Power
  // MaximumPower = Max_Current_Before_Overflow * VBUS_MAX
  // MaximumPower = 0.4 * 16V
  // MaximumPower = 6.4W
  
  // Set multipliers to convert raw current/power values
  ina219_currentDivider_mA = 20;  // Current LSB = 50uA per bit (1000/50 = 20)
  ina219_powerDivider_mW = 1;     // Power LSB = 1mW per bit

  // Set Calibration register to 'Cal' calculated above
  wireWriteRegister(INA219_REG_CALIBRATION, ina219_calValue);
  
  // Set Config register to take into account the settings above
  uint16_t config = INA219_CONFIG_BVOLTAGERANGE_16V |
                    INA219_CONFIG_GAIN_1_40MV |
                    INA219_CONFIG_BADCRES_12BIT |
                    INA219_CONFIG_SADCRES_12BIT_1S_532US |
                    INA219_CONFIG_MODE_SANDBVOLT_CONTINUOUS;
  wireWriteRegister(INA219_REG_CONFIG, config);
}

/**************************************************************************/
/*!
    @brief  Instantiates a new INA219 class
*/
/**************************************************************************/
Adafruit_INA219::Adafruit_INA219(uint8_t addr) {
  ina219_i2caddr = addr;
  ina219_currentDivider_mA = 0;
  ina219_powerDivider_mW = 0;
}

/**************************************************************************/
/*!
    @brief  Setups the HW (defaults to 32V and 2A for calibration values)
*/
/**************************************************************************/
void Adafruit_INA219::begin() {
  Wire.begin();   
  // Set chip to known config values to start
  ina219SetCalibration_32V_2A();
}

/**************************************************************************/
/*!
    @brief  Gets the raw bus voltage (16-bit signed integer, so +-32767)
*/
/**************************************************************************/
int16_t Adafruit_INA219::getBusVoltage_raw() {
  uint16_t value;
  wireReadRegister(INA219_REG_BUSVOLTAGE, &value);

  // Shift to the right 3 to drop CNVR and OVF and multiply by LSB
  return (int16_t)((value >> 3) * 4);
}

/**************************************************************************/
/*!
    @brief  Gets the raw shunt voltage (16-bit signed integer, so +-32767)
*/
/**************************************************************************/
int16_t Adafruit_INA219::getShuntVoltage_raw() {
  uint16_t value;
  wireReadRegister(INA219_REG_SHUNTVOLTAGE, &value);
  return (int16_t)value;
}

/**************************************************************************/
/*!
    @brief  Gets the raw current value (16-bit signed integer, so +-32767)
*/
/**************************************************************************/
int16_t Adafruit_INA219::getCurrent_raw() {
  uint16_t value;

  // Sometimes a sharp load will reset the INA219, which will
  // reset the cal register, meaning CURRENT and POWER will
  // not be available ... avoid this by always setting a cal
  // value even if it's an unfortunate extra step
  wireWriteRegister(INA219_REG_CALIBRATION, ina219_calValue);

  // Now we can safely read the CURRENT register!
  wireReadRegister(INA219_REG_CURRENT, &value);
  
  return (int16_t)value;
}

/**************************************************************************/
/*!
    @brief  Gets the shunt voltage in mV (so +-327mV)
*/
/**************************************************************************/
float Adafruit_INA219::getShuntVoltage_mV() {
  int16_t value;
  value = getShuntVoltage_raw();
  return value * 0.01;
}

/**************************************************************************/
/*!
    @brief  Gets the shunt voltage in volts
*/
/**************************************************************************/
float Adafruit_INA219::getBusVoltage_V() {
  int16_t value = getBusVoltage_raw();
  return value * 0.001;
}

/**************************************************************************/
/*!
    @brief  Gets the current value in mA, taking into account the
            config settings and current LSB
*/
/**************************************************************************/
float Adafruit_INA219::getCurrent_mA() {
  float valueDec = getCurrent_raw();
  valueDec /= ina219_currentDivider_mA;
  return valueDec;
}
  

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板凳
airwill| | 2014-12-10 23:21 | 只看该作者
数据读出来了, 那么我决定接口和时序应该没有问题, 接下来可能是设置和参考等方面的问题.
从器件的资料看:
The INA219 monitors both shunt drop and supply voltage, with programmable conversion times and filtering. A programmable calibration value, combined with an internal multiplier, enables direct readouts in amperes. An additional multiplying register calculates power in watts.
里面有 programmable calibration value, combined with an internal multiplier 应该需要处理.

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地板
独孤垂钓2003|  楼主 | 2014-12-11 09:46 | 只看该作者
今天把ShuntVoltage的寄存器值通过串口动态显示的主机上,发现16位的数值,低8为一直是FF,只有高8位在变化,所以每次数值改变的最小分辨率变成了255*10uV 。而在读取BusVoltage的时候,低8位数值有变化,不会全FF。不知道这种情况是不是和I2C的时序或MCU总线驱动能力有关?

Air版主说的问题,我再仔细看看资料,因为我的理解是,如果要直接从INA219读取电流和功率值得话,需要计算和配置那个Calibration寄存器,否则只是读取ShuntVoltage和BusVoltage就不需要配置。我再研究一下。

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5
comeon201208| | 2014-12-15 19:05 | 只看该作者
看来这个方案还是挺复杂的啊。。

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