Got confused on how to read ADXL356 from rawValues to g when connected to Teensy4.1

[New-to-codin]

I tried to convert the raw values to g, so that I can do further analysis like FFT, time domain and time-frequency domain analysis.

I got confused on how to interpret the datasheet as attached.

I don't really know if it is advisable to use the accelerometer timestamp , that is the micros().

const int X_AXIS_PIN = A9;  // Analog input pin for X-axis
const int Y_AXIS_PIN = A8;  // Analog input pin for Y-axis
const int Z_AXIS_PIN = A7;  // Analog input pin for Z-axis

void setup() {
  Serial.begin(2000000);  // Initialize serial communication
}

void loop() {
  int xData, yData, zData;

  // Read analog values from accelerometer
  xData = analogRead(X_AXIS_PIN);
  yData = analogRead(Y_AXIS_PIN);
  zData = analogRead(Z_AXIS_PIN);
  

  // Print the accelerometer data
  //Serial.print("X: ");
  Serial.print(micros());
  Serial.print(",");
  Serial.print(xData);
  Serial.print(",");
  Serial.print(yData);
  Serial.print(",");
  Serial.println(zData);

  //delay(500);  // Delay between readings
}

36984059,228,209,234
36984111,228,209,233
36984164,228,209,234
36984216,228,209,234
36984268,228,209,233
36984321,228,209,233
36984373,228,209,234
36984425,228,209,233
36984478,228,209,234
36984530,228,209,233
36984582,228,208,233
![C84DAF95-6D22-4E41-B326-E8B8FD341B4E|690x373](upload://kN4moN2ZuqgkCMWrbYsHnJxTw7f.jpeg)
![7F80A23D-5955-4882-ADEC-694E2CDF41A8|690x461](upload://XB5YbFE5oL9asjGoM83mKjditO.jpeg)

[jremington]

@New-to-codin

FFT, time domain and time-frequency domain analysis.

None of those operations require that you change units of measure. They work on any scale.

But as a hint: if you hold the board still with one axis vertical, it will report 1 g acceleration on that axis, on any selected scale, and zero g on any perfectly horizontal axis.

The scale factor will vary slightly, depending on which axis you choose. Recalibrate the sensor to make them equal, if you like.

[New-to-codin]

Many thanks for your response, so can I use the accelerometer raw values and use the micros() column as my time?

[jremington]

Yes. Keep in mind that to have both positive and negative accelerations, you need to subtract the zero-g reading from each axis.

Before you analyze sensor data, you must fully understand what the raw values mean.

[New-to-codin]

This is a page from the data sheet but I don't really understand how to get the positive and negative acceleration.

Please I am a novice , i got this when the accelerometer was held still.

29973143,222,222,242
29973195,222,222,242
29973247,222,222,242
29973300,222,222,242
29973352,223,222,242
29973404,222,222,242
29973457,222,222,242
29973509,222,222,242
29973561,223,222,242
29973614,222,222,242
29973666,222,222,242
29973718,222,222,242

[jremington]

@New-to-codin

i got this when the accelerometer was held still.

If X and Y are perfectly horizontal, and Z is up, then the zero g offsets on X and Y are 222 (corresponding to 0 g).

Assuming the same offset for Z, then the raw acceleration on the Z axis is 242-222 = 20 = +1 g.

If that is correct, flip the sensor over, with X and Y still perfectly horizontal, and you should see a reading of 202 along Z (-1 g).

This calibration tutorial is for a digital version of that accelerometer, but may give you some additional insight.

[New-to-codin]

Many thanks for the tutorials, and I have flipped the sensor

111250772,222,222,203
111250824,222,223,203
111250876,222,222,203
111250929,222,222,203
111250981,222,223,203