ADXL355 Data Acquisition Question (ODR)

Other Hardware Sensors
1

Hi everyone,

I'm currently working on a research project where I am using the ADXL355 accelerometer. I have carefully followed the instructions in the datasheet and other helpful posts on the forum to write my main source code.

#define DEVID_AD                 0x00
#define DEVID_MST                0x01
#define PARTID                   0x02
#define REVID                    0x03
#define STATUS                   0x04
#define FIFO_ENTRIES             0x05
#define TEMP2                    0x06
#define TEMP1                    0x07
#define XDATA3                   0x08
#define XDATA2                   0x09
#define XDATA1                   0x0A
#define YDATA3                   0x0B
#define YDATA2                   0x0C
#define YDATA1                   0x0D
#define ZDATA3                   0x0E
#define ZDATA2                   0x0F
#define ZDATA1                   0x10
#define FIFO_DATA                0x11
#define OFFSET_X_H               0x1E
#define OFFSET_X_L               0x1F
#define OFFSET_Y_H               0x20
#define OFFSET_Y_L               0x21
#define OFFSET_Z_H               0x22
#define OFFSET_Z_L               0x23
#define ACT_EN                   0x24
#define ACT_THRESH_H             0x25
#define ACT_THRESH_L             0x26
#define ACT_COUNT                0x27
#define FILTER                   0x28
#define FIFO_SAMPLES             0x29
#define INT_MAP                  0x2A
#define SYNC                     0x2B
#define RANGE                    0x2C
#define POWER_CTL                0x2D
#define SELF_TEST                0x2E
#define RESET                    0x2F

#define ADXL355_CS_PIN    10
#define ADXL355_MOSI_PIN  11
#define ADXL355_MISO_PIN  12
#define ADXL355_SCK_PIN   13

#include <Arduino.h>
//#include <SD.h>
#include "SdFat.h"
#include <Wire.h>
#include <SPI.h>
#include <led.h>

//const int SD_CS = 8;
const int acc_CS = 10; //
long values[20],t[9];
double x, y, z, c;

volatile uint8_t ADXL355_DRDY;
volatile int ADXL355_DATA_COUNTER;

void acc_data();
byte readRegister (byte thisRegister);
void writeRegister (byte thisRegister, byte value);

SdFat SDO;
File myFile;

void GPIO7_IRQHandler(void) {
    if (1) {
        ADXL355_DRDY = 1;
        ADXL355_DATA_COUNTER += 1;
    }
}

void setup() { 
  delay(1000);
  Serial.begin(115200);
  
  SPI.setMOSI(ADXL355_MOSI_PIN);
  SPI.setSCK(ADXL355_SCK_PIN);
  SPI.setMISO(ADXL355_MISO_PIN);
  SPI.setCS(ADXL355_CS_PIN);
  SPI.begin();

  pinMode(3, OUTPUT);
  digitalWrite(3, HIGH);

  pinMode(41, OUTPUT);
  digitalWrite(41, HIGH);

  pinMode(10, OUTPUT);
  digitalWrite(10, HIGH);

  pinMode(6, INPUT);
  attachInterrupt(digitalPinToInterrupt(6), GPIO7_IRQHandler, RISING);

  digitalWrite(3, HIGH);
  digitalWrite(10, HIGH);
//  digitalWrite(23, HIGH);
  
  writeRegister(POWER_CTL, 0x00);
  writeRegister(RANGE, 0xC1);
  writeRegister(SELF_TEST, 0x00);  // writing 0 to to enable sensor // 0x06?
  writeRegister(SYNC, 0x00);
  writeRegister(FILTER, 0x05); // 1000 Hz
  delay(500);

  ADXL355_DRDY = 0;
  ADXL355_DATA_COUNTER = 0;

  SDO.begin(SdioConfig(FIFO_SDIO));

  LED_Init();
  LED_Off();
}
void loop() {
  
  ADXL355_DRDY = 0;
  ADXL355_DATA_COUNTER = 0;

  for (int i=0; i<4000*60*10; i++) {
    while (!ADXL355_DRDY) {}
        ADXL355_DRDY = 0;
        acc_data();
        if (i%10 == 0){
            Serial.print(ADXL355_DATA_COUNTER);
            Serial.print(',');
            Serial.print(x,7);
            Serial.print(',');
            Serial.print(y,7);
            Serial.print(',');
            Serial.print(z,7);
            Serial.println();
        }
        if (i%1000 == 0){
            LED_Gtoggle();
        }
  }
//   acc_data();
  
//   delay(3000);
}

byte readRegister (byte thisRegister) {
  byte inByte = 0 ;
  digitalWrite(acc_CS, LOW); 
  SPI.transfer((thisRegister << 1) | 1);
  inByte = SPI.transfer(0x00);
  digitalWrite(acc_CS, HIGH);
  return inByte;
}
void writeRegister (byte thisRegister, byte value) {
  digitalWrite(acc_CS, LOW);
  SPI.transfer(thisRegister << 1);
  SPI.transfer(value);
  digitalWrite(acc_CS, HIGH);
}
void acc_data(){
  values[0] = readRegister(XDATA3);
  values[1] = readRegister(XDATA2);
  values[2] = readRegister(YDATA3);
  values[3] = readRegister(YDATA2);
  values[4] = readRegister(ZDATA3);
  values[5] = readRegister(ZDATA2);

  values[6] = readRegister(XDATA1);
  values[7] = readRegister(YDATA1);
  values[8] = readRegister(ZDATA1);

  t[0] = readRegister(TEMP2);
  t[1] = readRegister(TEMP1);

  x = (values[0] << 12) + (values[1]<<4) + (values[6]>>4);
  y = (values[2] << 12) + (values[3]<<4) + (values[7]>>4);
  z = (values[4] << 12) + (values[5]<<4) + (values[8]>>4);

//  Serial.print(x);Serial.print(",");
//  Serial.print(y);Serial.print(",");
//  Serial.print(z);Serial.println();
   
  if (x >= 0x80000) {
    x = x-(2*0x80000);
  }
  if (y >= 0x80000) {
    y = y-(2*0x80000);
  }
  if (z >= 0x80000) {
    z = z-(2*0x80000);
  }
 
  c=(t[0]<<8)+t[1];
  c=((1852 - c)/9.05)+25.7;
 
  x=x*0.0000039;
  y=y*0.0000039;
  z=z*0.0000039;
  }

However, I have encountered an issue with the ADXL355 ODR settings. Despite setting the ODR correctly in my code, I have observed through an oscilloscope that the DRDY pin does not reflect the expected output.

image
image1368×648 73.7 KB

image
image1368×648 73.5 KB

Similarly, when I change ODR from 4000Hz(Addr:0x28->Val:0x00) to 125Hz(Addr:0x28->Val:0x05), each output doesn't give its exact setting value..

ODR=0 : (ideal) 4000Hz <-> (measured) 3968Hz~4098Hz
ODR=1 : (ideal) 2000Hz <-> (measured) 2000Hz~2032Hz
ODR=2 : (ideal) 1000Hz <-> (measured) 1012Hz~1016Hz
ODR=3 : (ideal) 500Hz <-> (measured) 502.5Hz~507.6Hz
ODR=4 : (ideal) 250Hz <-> (measured) 126.6Hz~252.5Hz
ODR=5 : (ideal) 125Hz <-> (measured) ~126.3Hz

Low odr even gives high difference..
Also It seems that data lost breaks out

I wanted to ask if anyone else has experienced a similar problem with the ADXL355 accelerometer. If so, I would appreciate any insights or solutions you have discovered to address this issue.

Thank you in advance for your help and suggestions.

Best regards,

2

Why do you expect the rate to be "exact"? The sensor does not have a precision crystal clock.

Check the data sheet for information about using an external clock for synchronization.

1 Like
3

Thank you for your reply

I have also read the datasheet and I understand that using a 1.024MHz external clock can improve accuracy. However, I expected the accelerometer to provide reasonably accurate values at a sampling rate of 1000Hz since it doesn't require super-high requirement in my point of view.

But last night, I succeeded to match the sampling time precisely by changing the attachinginterrupt setting from RISING to HIGH.

image
image1368×648 67.4 KB

I also tested the ADXL355 accelerometer by exciting a 3Hz sinusoidal signal using a shaking table and comparing its performance with a reference sensor. The ADXL355 accurately captured the signal's frequency without any noticeable changes.

image
image1218×451 73.7 KB

But there is still one problem left.. that is its absolute value differs with reference sensor
Although ADXL355 is digital sensor, it is so noisy more than i expected

image
image1218×971 150 KB

I suspect that there is wrong with my source code or there could be a conversion mistake occurred
If you or anyone have any insights or guidance regarding this issue, please let me know

Here's the source code now i'm using

#define DEVID_AD                 0x00
#define DEVID_MST                0x01
#define PARTID                   0x02
#define REVID                    0x03
#define STATUS                   0x04
#define FIFO_ENTRIES             0x05
#define TEMP2                    0x06
#define TEMP1                    0x07
#define XDATA3                   0x08
#define XDATA2                   0x09
#define XDATA1                   0x0A
#define YDATA3                   0x0B
#define YDATA2                   0x0C
#define YDATA1                   0x0D
#define ZDATA3                   0x0E
#define ZDATA2                   0x0F
#define ZDATA1                   0x10
#define FIFO_DATA                0x11
#define OFFSET_X_H               0x1E
#define OFFSET_X_L               0x1F
#define OFFSET_Y_H               0x20
#define OFFSET_Y_L               0x21
#define OFFSET_Z_H               0x22
#define OFFSET_Z_L               0x23
#define ACT_EN                   0x24
#define ACT_THRESH_H             0x25
#define ACT_THRESH_L             0x26
#define ACT_COUNT                0x27
#define FILTER                   0x28
#define FIFO_SAMPLES             0x29
#define INT_MAP                  0x2A
#define SYNC                     0x2B
#define RANGE                    0x2C
#define POWER_CTL                0x2D
#define SELF_TEST                0x2E
#define RESET                    0x2F

#define ADXL355_CS_PIN    10
#define ADXL355_MOSI_PIN  11
#define ADXL355_MISO_PIN  12
#define ADXL355_SCK_PIN   13

#include <Arduino.h>
//#include <SD.h>
#include "SdFat.h"
#include <Wire.h>
#include <SPI.h>
#include <led.h>

//const int SD_CS = 8;
const int acc_CS = 10; //
long values[20],t[9];
double x, y, z, c;

volatile uint8_t ADXL355_DRDY;
volatile int ADXL355_DATA_COUNTER;

String fileName;
int fileCount = 1;

void acc_data();
byte readRegister (byte thisRegister);
void writeRegister (byte thisRegister, byte value);

SdFat SDO;
File myFile;

void GPIO7_IRQHandler(void) {
    if (1) {
        ADXL355_DRDY = 1;
        ADXL355_DATA_COUNTER += 1;
    }
}

void setup() { 
  delay(1000);
  Serial.begin(115200);
  
  SPI.setMOSI(ADXL355_MOSI_PIN);
  SPI.setSCK(ADXL355_SCK_PIN);
  SPI.setMISO(ADXL355_MISO_PIN);
  SPI.setCS(ADXL355_CS_PIN);
  SPI.begin();

  pinMode(3, OUTPUT);
  digitalWrite(3, HIGH);

  pinMode(41, OUTPUT);
  digitalWrite(41, HIGH);

  pinMode(10, OUTPUT);
  digitalWrite(10, HIGH);

  pinMode(6, INPUT);
  attachInterrupt(digitalPinToInterrupt(6), GPIO7_IRQHandler, HIGH);

  digitalWrite(3, HIGH);
  digitalWrite(10, HIGH);
//  digitalWrite(23, HIGH);
  
  writeRegister(POWER_CTL, 0x00);
  writeRegister(RANGE, 0xC1);
  writeRegister(SELF_TEST, 0x00);  // writing 0 to to enable sensor // 0x06?
  writeRegister(SYNC, 0x00);
  writeRegister(FILTER, 0x02); // 1000 Hz
  delay(500);

  ADXL355_DRDY = 0;
  ADXL355_DATA_COUNTER = 0;

  SDO.begin(SdioConfig(FIFO_SDIO));

  LED_Init();
  LED_Off();
}
void loop() {
  
  ADXL355_DRDY = 0;
  ADXL355_DATA_COUNTER = 0;
 
  fileName = String(fileCount) + ".txt";
  myFile = SDO.open(fileName, O_WRITE | O_CREAT | O_APPEND) ;

  for (int i=0; i<1000*60*1; i++) {
    while (!ADXL355_DRDY) {}
        ADXL355_DRDY = 0;
        acc_data();
        if (i%10 == 0){
            myFile.print(i);
            myFile.print(',');
            myFile.print(x,7);
            myFile.print(',');
            myFile.print(y,7);
            myFile.print(',');
            myFile.print(z,7);
            myFile.println();
        }
        if (i%1000 == 0){
            LED_Gtoggle();
        }
  }
  myFile.close();
  fileCount++;
//   acc_data();
  
//   delay(3000);
}

byte readRegister (byte thisRegister) {
  byte inByte = 0 ;
  digitalWrite(acc_CS, LOW); 
  SPI.transfer((thisRegister << 1) | 1);
  inByte = SPI.transfer(0x00);
  digitalWrite(acc_CS, HIGH);
  return inByte;
}
void writeRegister (byte thisRegister, byte value) {
  digitalWrite(acc_CS, LOW);
  SPI.transfer(thisRegister << 1);
  SPI.transfer(value);
  digitalWrite(acc_CS, HIGH);
}
void acc_data(){
  values[0] = readRegister(XDATA3);
  values[1] = readRegister(XDATA2);
  values[2] = readRegister(YDATA3);
  values[3] = readRegister(YDATA2);
  values[4] = readRegister(ZDATA3);
  values[5] = readRegister(ZDATA2);

  values[6] = readRegister(XDATA1);
  values[7] = readRegister(YDATA1);
  values[8] = readRegister(ZDATA1);

  t[0] = readRegister(TEMP2);
  t[1] = readRegister(TEMP1);

  x = (values[0] << 12) + (values[1]<<4) + (values[6]>>4);
  y = (values[2] << 12) + (values[3]<<4) + (values[7]>>4);
  z = (values[4] << 12) + (values[5]<<4) + (values[8]>>4);

//  Serial.print(x);Serial.print(",");
//  Serial.print(y);Serial.print(",");
//  Serial.print(z);Serial.println();
   
  if (x >= 0x80000) {
    x = x-(2*0x80000);
  }
  if (y >= 0x80000) {
    y = y-(2*0x80000);
  }
  if (z >= 0x80000) {
    z = z-(2*0x80000);
  }
 
  c=(t[0]<<8)+t[1];
  c=((1852 - c)/9.05)+25.7;
 
  x=x*0.0000039;
  y=y*0.0000039;
  z=z*0.0000039;
  }
4

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