Hello I bought 3 accelerometers and it seems that none of which is working properly, in particular positions, as on the picture when the acceleration should be as below picture, readings numbers are different, and aren’t even close to correct value ( I didn’t put any values for the offset registers so lets say only difference in values between positions is the issue).
My question is are those accelerometers definetly corrupted or is it some other issue that could be solved somehow, I include data sheet for adxl345 accelerometer and order of position I made measurements and code which is mostly copied from sparkfun basic example.
Those are measurements with 10 bits resolution:
position1// 8 :-24,-11,-123 9 :-105,-117,31 10 :-2,-19,91
position2// 8 :-24,-13,63 9 :-103,-118,-21 10 :-5,-18,18
position3// 8 :-25,28,98 9 :-103,-88,7 10 :-5,16,61
position4// 8 :-26,-49,97 9 :-104,-148,5 10 :-2,-50,53
position5// 8 :15,-14,99 9 :-72,-118,7 10 :31,-17,54
position6// 8 :-64,-10,97 9 :-134,-117,3 10 :-37,-17,58
Those are measurements with 13 bits resolution:
position1// 8 :-182,-47,-43 9 :-56,-975,-166 10 :-27,-67,-95
position2// 8 :-198,-130,1067 9 :-72,-706,81 10 :-1,-392,-67
position3// 8 :-171,-23,791 9 :-66,-704,51 10 :0,-127,-9
position4// 8 :-172,-389,-13 9 :-80,-1188,53 10 :-7,-397,-84
position5// 8 :-511,-60,-26 9 :-52,-928,32 10 :-9,-138,-70
position6// 8 :-126,-74,787 9 :-62,-928,66 10 :-39,-159,-25
//Add the SPI library so we can communicate with the ADXL345 sensor
#include <SPI.h>
#include <LiquidCrystal.h>
LiquidCrystal lcd(2, 3, 4, 5, 6, 7);
//Assign the Chip Select signal to pin 10.
//This is a list of some of the registers available on the ADXL345.
//To learn more about these and the rest of the registers on the ADXL345, read the datasheet!
char POWER_CTL = 0x2D; //Power Control Register
char DATA_FORMAT = 0x31;
char DATAX0 = 0x32; //X-Axis Data 0
char DATAX1 = 0x33; //X-Axis Data 1
char DATAY0 = 0x34; //Y-Axis Data 0
char DATAY1 = 0x35; //Y-Axis Data 1
char DATAZ0 = 0x36; //Z-Axis Data 0
char DATAZ1 = 0x37; //Z-Axis Data 1
char OFSX = 0x1E; //Z-Axis offset
char OFSY = 0x1F; //Z-Axis offset
char OFSZ = 0x20; //Z-Axis offset
//This buffer will hold values read from the ADXL345 registers.
char values[10];
//These variables will be used to hold the x,y and z axis accelerometer values.
float x,y,z;
int x1,y1,z1;
int j,k;
int CS=8;
int analogPin = 1;
int button=0;
void setup(){
//Initiate an SPI communication instance.
SPI.begin();
//Configure the SPI connection for the ADXL345.
SPI.setDataMode(SPI_MODE3);
//Create a serial connection to display the data on the terminal.
Serial.begin(9600);
//Set up the Chip Select pin to be an output from the Arduino.
pinMode(8, OUTPUT); //cs
pinMode(9, OUTPUT);
pinMode(10, OUTPUT); //cs
//Before communication starts, the Chip Select pin needs to be set high.
digitalWrite(8, HIGH);
digitalWrite(9, HIGH);
digitalWrite(10, HIGH);
writeRegister(OFSX,0x00);//zerowanie offsetów
writeRegister(OFSY,0x00);//zerowanie offsetów
writeRegister(OFSZ,0x00);//zerowanie offsetów
//Put the ADXL345 into +/- 2G range by writing the value 0x00 to the DATA_FORMAT register.
writeRegister(DATA_FORMAT,0x01| 0x02| 0x08);
//Put the ADXL345 into Measurement Mode by writing 0x08 to the POWER_CTL register.
writeRegister(POWER_CTL, 0x08); //Measurement mode
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.display();
}
void loop(){
if(button = analogRead(analogPin)>500){
//Reading 6 bytes of data starting at register DATAX0 will retrieve the x,y and z acceleration values from the ADXL345.
//The results of the read operation will get stored to the values[] buffer.
for(j=0;j<3;j++){
Serial.print(CS+j);
Serial.print(" :");
readRegister(DATAX0, 6, values);
//The ADXL345 gives 10-bit acceleration values, but they are stored as bytes (8-bits). To get the full value, two bytes must be combined for each axis.
//The X value is stored in values[0] and values[1].
x1 = ((int)values[1]<<8)|(int)values[0];
//The Y value is stored in values[2] and values[3].
y1 = ((int)values[3]<<8)|(int)values[2];
//The Z value is stored in values[4] and values[5].
z1 = ((int)values[5]<<8)|(int)values[4];
x=x1/1.0f;
y=y1/1.0f;
z=z1/1.0f;
//Print the results to the terminal.
Serial.print(x, 5);
Serial.print(',');
Serial.print(y, 5);
Serial.print(',');
Serial.println(z, 5);
delay(10);
lcd.clear();
lcd.print("x=");
lcd.print(x, 2);
lcd.print(", ");
lcd.print("y=");
lcd.print(y, 2);
lcd.print(',');
lcd.setCursor(2, 1);
lcd.print("z=");
lcd.print(z, 2);
lcd.print(" (g)");
lcd.setCursor(0, 1);
delay(500);
lcd.clear();
}
j=0;
CS=8;
}
}
//This function will write a value to a register on the ADXL345.
//Parameters:
// char registerAddress - The register to write a value to
// char value - The value to be written to the specified register.
void writeRegister(char registerAddress, char value){
for(k=0;k<3;k++){
//Set Chip Select pin low to signal the beginning of an SPI packet.
digitalWrite(CS+k, LOW);
//Transfer the register address over SPI.
SPI.transfer(registerAddress);
//Transfer the desired register value over SPI.
SPI.transfer(value);
//Set the Chip Select pin high to signal the end of an SPI packet.
digitalWrite(CS+k, HIGH);
}
j=0;
delay(10);
}
//This function will read a certain number of registers starting from a specified address and store their values in a buffer.
//Parameters:
// char registerAddress - The register addresse to start the read sequence from.
// int numBytes - The number of registers that should be read.
// char * values - A pointer to a buffer where the results of the operation should be stored.
void readRegister(char registerAddress, int numBytes, char * values){
//Since we're performing a read operation, the most significant bit of the register address should be set.
char address = 0x80 | registerAddress;
//If we're doing a multi-byte read, bit 6 needs to be set as well.
if(numBytes > 1)address = address | 0x40;
//Set the Chip select pin low to start an SPI packet.
digitalWrite(CS+j, LOW);
//Transfer the starting register address that needs to be read.
SPI.transfer(address);
//Continue to read registers until we've read the number specified, storing the results to the input buffer.
for(int i=0; i<numBytes; i++){
values[i] = SPI.transfer(0x00);
}
//Set the Chips Select pin high to end the SPI packet.
digitalWrite(CS+j, HIGH);
delay(10);
}
ADXL345.pdf (482 KB)
