CODEWITHSUNDEEP
arduinoaccelerometeri2cesp32
Aryaman Patel
Aryaman Patel

Reputation: 1

ADXL345 with ESP32 I2C garbage value issue

I have connected my ESP32 with ADXL345 using I2C interface according to the tutorial followed from Tutorial

However, when I run the code with the sensor flat on the table, shouldn't I be getting an output close to X = 0.04, Y = 0.04, Z = 9.81 m/s^2. However, this is the output I am getting:

22:26:29.569 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.604 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.639 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.672 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.705 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.739 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.772 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.806 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.873 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.908 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.942 -> Xa= 254.00   Ya= 254.00   Za= 2.00
22:26:29.975 -> Xa= 254.00   Ya= 254.00   Za= 2.00

Moreover, the X and Y output do not change when I move the sensor.

Here is the code I am using :

#include <Wire.h>  // Wire library - used for I2C communication

int ADXL345 = 0x53; // The ADXL345 sensor I2C address

float X_out, Y_out, Z_out;  // Outputs

void setup() {
  Serial.begin(9600); // Initiate serial communication for printing the 
                         results on the Serial monitor
  Wire.begin(); // Initiate the Wire library
  // Set ADXL345 in measuring mode
  Wire.beginTransmission(ADXL345); // Start communicating with the device 
  Wire.write(0x2D); // Access/ talk to POWER_CTL Register - 0x2D
  // Enable measurement
  Wire.write(8); // (8dec -> 0000 1000 binary) Bit D3 High for measuring enable 
  Wire.endTransmission();
  delay(10);
}

void loop() {
  // === Read acceleromter data === //
  Wire.beginTransmission(ADXL345);
  Wire.write(0x32); // Start with register 0x32 (ACCEL_XOUT_H)
  Wire.endTransmission(false);
  Wire.requestFrom(ADXL345, 6, true); // Read 6 registers total, each axis value is stored in 2 registers
  X_out = ( Wire.read()| Wire.read() << 8); // X-axis value
  X_out = X_out/256; //For a range of +-2g, we need to divide the raw values by 256, according to the datasheet
  Y_out = ( Wire.read()| Wire.read() << 8); // Y-axis value
  Y_out = Y_out/256;
  Z_out = ( Wire.read()| Wire.read() << 8); // Z-axis value
  Z_out = Z_out/256;

  Serial.print("Xa= ");
  Serial.print(X_out);
  Serial.print("   Ya= ");
  Serial.print(Y_out);
  Serial.print("   Za= ");
  Serial.println(Z_out);
}

UPDATES: Here is an Update to the output after making the suggested changes:

22:14:43.271 -> Xa= -2   Ya= -2   Za= 1
22:14:43.271 -> Xa= -2   Ya= -2   Za= 1
22:14:43.304 -> Xa= -2   Ya= -2   Za= 1
22:14:43.337 -> Xa= -2   Ya= -2   Za= 1
22:14:43.370 -> Xa= -2   Ya= -2   Za= 1
22:14:43.403 -> Xa= -2   Ya= -2   Za= 1
22:14:43.403 -> Xa= -2   Ya= -2   Za= 1
22:14:43.437 -> Xa= -2   Ya= -2   Za= 1
22:14:43.471 -> Xa= -2   Ya= -2   Za= 1

Here is the updated code:

#include <Wire.h>  // Wire library - used for I2C communication

int ADXL345 = 0x53; // The ADXL345 sensor I2C address

int16_t X_out, Y_out, Z_out;  // Outputs

void setup() {
  Serial.begin(9600); // Initiate serial communication for printing the 
                       //  results on the Serial monitor
  Wire.begin(); // Initiate the Wire library
  // Set ADXL345 in measuring mode
  Wire.beginTransmission(ADXL345); // Start communicating with the device 
  Wire.write(0x2D); // Access/ talk to POWER_CTL Register - 0x2D
  // Enable measurement
  Wire.write(8); // (8dec -> 0000 1000 binary) Bit D3 High for measuring enable 
  Wire.endTransmission();
  delay(10);
}

void loop() {
  // === Read acceleromter data === //
  Wire.beginTransmission(ADXL345);
  Wire.write(0x32); // Start with register 0x32 (ACCEL_XOUT_H)
  Wire.endTransmission(false);
  Wire.requestFrom((uint16_t)ADXL345,(uint8_t) 6, true); // Read 6 registers total, each axis value is stored in 2 registers
  X_out = ( Wire.read()| Wire.read() << 8); // X-axis value
  X_out = X_out/256; //For a range of +-2g, we need to divide the raw values by 256, according to the datasheet
  Y_out = ( Wire.read()| Wire.read() << 8); // Y-axis value
  Y_out = Y_out/256;
  Z_out = ( Wire.read()| Wire.read() << 8); // Z-axis value
  Z_out = Z_out/256;

  Serial.print("Xa= ");
  Serial.print(X_out);
  Serial.print("   Ya= ");
  Serial.print(Y_out);
  Serial.print("   Za= ");
  Serial.println(Z_out);
}

The values of the Z axis does not seem to be changing when I change the orientation of the ADXL345 sensor. How could we solve this prolem?

Upvotes: 0

Views: 832

Answers (1)

Tarmo
Tarmo

Reputation: 4762

Firstly, your code and output don't match. Secondly, in your code you're reading a 2-byte signed integer value from a register and assigning it to a variable of type float. This will result in garbage. Use the correct type of variable (int16_t in this case). The data sheet for the accelerometer specifies the data format (section "Register 0x32 to Register 0x37—DATAX0, DATAX1, DATAY0, DATAY1, DATAZ0, DATAZ1 (Read Only)")

Upvotes: 0

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