ADXL373加速度计SPI通信问​​题

Question

作为序言，我是Arduino和电子通信的新手。我处于基于Arduino的加速度计设置的初始阶段，以记录撞击的高加速度尖峰。我正在与单个ADXL373加速度计通过SPI启动。

我已经陷入了SPI代码上一段时间，因为它只能从所有3个轴上读取0。我期望的问题仍在编码我的读物/写作方面仍然存在。在我执行它们时，是否有什么明显的脱颖而出的？

adxl373数据表：

// ADXL373 400g Accelerometer sensor connected to Arduino 2560 Mega Board

// V5: pin 3.3V
// GND: pin GND
// MOSI: pin 51
// MISO: pin 50
// SCLK: pin 52
// CS: pin 53

// the sensor communicates using SPI, so include the library:
#include <SPI.h>

const int CS = 53; //Chip Select (Arduino Mega Pin 53)

/////////////////////////////////////////////////////////////////////////////////
///////////////////////////// Register Addresses ////////////////////////////////

byte XDATA_H = 0x08; // (0b00001000) X Data Register, High 8 MSB 
byte XDATA_L = 0x09; // (0b00001001) X Data Register, Low 4 MSB 
byte YDATA_H = 0x0A; // (0b00001010) Y Data Register, High 8 MSB 
byte YDATA_L = 0x0B; // (0b00001011) Y Data Register, Low 4 MSB 
byte ZDATA_H = 0x0C; // (0b00001100) Z Data Register, High 8 MSB 
byte ZDATA_L = 0x0D; // (0b00001101) Z Data Register, Low 4 MSB 
byte OFFSET_X = 0x20; // X Data Offset Register, Lower 4 bits
byte OFFSET_Y = 0x21; // Y Data Offset Register, Lower 4 bits
byte OFFSET_Z = 0x22; // Z Data Offset Register, Lower 4 bits
byte TIME_CTRL = 0x3D; // (0b00111101) Timing Control Register -> Select ODR (0b10000000) for 5120 Hz
byte MEASR_CTRL = 0x3E; // (0b00111110) Measurement Control -> Bandwidth set (0b00000100) for 2560 Hz
byte POWER_CTRL = 0x3F; // (0b00111111) Power Control Register -> Op. Mode and HPF off (0b00000111)
const byte WRITE = 0b11111110; // Reads with a 1, high
const byte READ = 0b00000001; // Writes with a 0, low

////////////////////////////////////////////////////////////////////////////////

// Establish variables to identify x, y, and z axis accelerations
int x_axis = 1;
int y_axis = 2;
int z_axis = 3;

void setup() 
{
  SPI.begin(); // Initialize SPI
  SPI.setDataMode(SPI_MODE0);
  SPI.setBitOrder(MSBFIRST); // Data for the device is sent MSB first, RW is last bit
  Serial.begin(115200);   // Establish a serial connection to display data through terminal
  pinMode(CS, OUTPUT);   // Set CS Pin Direction
  digitalWrite(CS, LOW);
  writeRegister(MEASR_CTRL, 0b00000100); // Set Measurement Mode to 2560Hz bandwidth (0x04)
  writeRegister(POWER_CTRL, 0b00000111); // Set full bandwidth measurement mode, HPF disabled (0x07)
  writeRegister(TIME_CTRL, 0b10000000); // Set ODR to 5120 Hz
  digitalWrite(CS, HIGH);
  delay(1);
}

void loop()
{
  Serial.print(" x = "); 
  Serial.print(getValue(x_axis));
  Serial.print(" y = "); 
  Serial.print(getValue(y_axis));
  Serial.print(" z = "); 
  Serial.println(getValue(z_axis));
  delay(0.2);
}

int getValue(int axis)
{
  int AccelData = 0;
  int Offset = 0;
  int high, low; 
  if (axis == 1)
  {
    high = readRegister(XDATA_H);
    low = readRegister(XDATA_L);
  }
  else if (axis == 2)
  {
    high = readRegister(YDATA_H);
    low = readRegister(YDATA_L);
  }
  else if (axis == 3)
  {
    high = readRegister(ZDATA_H);
    low = readRegister(ZDATA_L);
  }
  AccelData = (high << 4) | (low >> 4); // Merge 8 bits from 'high' with upper 4 of 'low' 
  AccelData = (AccelData - Offset)*200; // (Reading-Offset)*ScaleFactor --> 200mg/LSB for ADXL373
  return AccelData;
}

byte readRegister(byte thisRegister)
{
  byte result = 0;   // predeclare result to return
  // ADXL373 expects the register address in the upper 7 bits of the transmitted byte
  // Shift the register bits left by 1 to apply READ bit:
  thisRegister = thisRegister << 1;
  byte dataToSend = thisRegister | READ; // Combine register address with READ command
  digitalWrite(CS,LOW);  //Set the Chip Select pin low to start an SPI packet
  result = SPI.transfer(dataToSend);  // Tell device to read register and save response
  digitalWrite(CS, HIGH);  //Set CS high to close communcation
  return result;
}

void writeRegister(byte thisRegister, byte thisValue)
{
 // ADXL373 expects the register address in the upper 7 bits of the transmitted byte
 // Shift the register bits left by 1 bit to apply WRITE bit:
 thisRegister = thisRegister << 1;
 byte dataWrite = thisRegister & WRITE; // Combine the register address and WRITE command
 byte dataToSend = ((dataWrite << 8) | thisValue);
 digitalWrite(CS,LOW); //Set CS pin low to signal SPI packet start
 SPI.transfer(dataToSend); //Transfer the register address, RW, and desired register value over SPI
 digitalWrite(CS,HIGH); //Set the Chip Select pin high to signal the end of an SPI packet.
}

任何指导都非常感谢。

Answer 1

您需要使用两个spi.transfer（）语句，例如在用于气压传感器。请参阅第160-164行：

158   // send the device the register you want to read:
159 
160   SPI.transfer(dataToSend);
161 
162   // send a value of 0 to read the first byte returned:
163 
164   result = SPI.transfer(0x00);

第一个语句告诉传感器您要阅读的注册。第二个语句返回数据（此示例中的传感器不像您的ADXL完全工作，因此我认为您不必发送0x00才能启动读取，但是要点是相同的）。

spi.transfer（）说的描述它执行“同时发送和接收”，但也可以用作发送或接收。