[KX134] Are ODR higher then 200Hz possible?

[delijati]

I tried to set the ODR to 8 (200Hz) and 13 (3200Hz) but serial output only gives me a fraction of the 3200Hz. (expected 10s x 3200 == 32000 samples). Is there something i can configure, adjust?

Spark thing plus:

❯ arduino-cli upload -p /dev/ttyUSB0 --fqbn esp32:esp32:esp32thing_plus default
esptool.py v4.5.1
Serial port /dev/ttyUSB0
Connecting....
Chip is ESP32-D0WD-V3 (revision v3.0)
Features: WiFi, BT, Dual Core, 240MHz, VRef calibration in efuse, Coding Scheme None
Crystal is 40MHz

Runs:

$ # 3200Hz:
$ python log.py; cat dataFile.txt | wc -l
saved lines: 3562
3562
$ # 200Hz
$ python log.py; cat dataFile.txt | wc -l
saved lines: 2010
2010

Arduino code:

/*
  example3-Buffer

  This example shows both how to setup the buffer but also how to route the buffer's
  interrupt to a physical interrupt pin.

  Written by Elias Santistevan @ SparkFun Electronics, October 2022

  Products:

  SparkFun Triple Axis Accelerometer Breakout - KX132:
    https://www.sparkfun.com/products/17871

  SparkFun Triple Axis Accelerometer Breakout - KX134:
    https://www.sparkfun.com/products/17589


  Repository:

    https://github.com/sparkfun/SparkFun_KX13X_Arduino_Library

  SparkFun code, firmware, and software is released under the MIT
  License	(http://opensource.org/licenses/MIT).
*/

#include <Wire.h>
#include <SparkFun_KX13X.h> // Click here to get the library: http://librarymanager/All#SparkFun_KX13X

SparkFun_KX134 kxAccel;
// SparkFun_KX134 kxAccel; // For the KX134, uncomment this and comment line above

outputData myData;     //  Struct for the accelerometer's data
byte dataReadyPin = 2; //  Change to fit your project.

void setup()
{

  Wire.begin();

  Serial.begin(115200);
  Serial.println("Welcome.");

  // Wait for the Serial monitor to be opened.
  while (!Serial)
    delay(50);

  if (!kxAccel.begin())
  {
    Serial.println("Could not communicate with the the KX13X. Freezing.");
    while (1)
      ;
  }

  Serial.println("Ready.");

  // Reset the chip so that old settings don't apply to new setups.
  if (kxAccel.softwareReset())
    Serial.println("Reset.");

  // Give some time for the accelerometer to reset.
  // It needs two, but give it five for good measure.
  delay(5);

  // Many settings for KX13X can only be
  // applied when the accelerometer is powered down.
  // However there are many that can be changed "on-the-fly"
  // check datasheet for more info, or the comments in the
  // "...regs.h" file which specify which can be changed when.
  kxAccel.enableAccel(false);

  kxAccel.enableBufferInt();            //  Enables the Buffer interrupt
  kxAccel.enablePhysInterrupt();        //  Enables interrupt pin 1
  kxAccel.routeHardwareInterrupt(0x40); //  Routes the data ready bit to pin 1

  kxAccel.enableSampleBuffer();         // Enable buffer.
  kxAccel.setBufferOperationMode(0x00); // Enable the buffer to be FIFO.
  kxAccel.setOutputDataRate(8); // 200 Hz
  // kxAccel.setOutputDataRate(12); // 3200 Hz

  // Additional Buffer Settings

  // uint8_t numSamples = 140;
  // kxAccel.setBufferThreshold(numSamples);   //  Set the number of sample that can be stored in the buffer

  kxAccel.setBufferResolution(); //  Change sample resolution to 16 bit, 8 bit by default.
                                 //  This will change how many samples can be held in buffer.
                                 //  Comment the above line if you want to try using 8-bit data.

  // kxAccel.clearBuffer();                    //  Clear the buffer
  // kxAccel.getSampleLevel();                 //  Get the number of samples in the buffer. This number
                                               //   Changes depending on the resolution, see datasheet for more info.

  // kxAccel.setRange(SFE_KX132_RANGE2G); // 2g Range
  kxAccel.setRange(SFE_KX134_RANGE8G);      // 8g for the KX134

  // kxAccel.setOutputDataRate(); //  Default is 50Hz
  kxAccel.enableAccel();
}

void loop()
{

  // We could use the KX13X interrupt pin and dataReadyPin to indicate when data is ready.
  // But we can also use getSampleLevel. getSampleLevel will return how much data is in the buffer.
  if (kxAccel.getSampleLevel() > 0)
  {
    /*
        // getAccelData is slow as it manually checks if the buffer is being used
        // and if the data resolution is 16-bit or 8-bit.
        if (kxAccel.getAccelData(&myData) == true)
        {
          Serial.println();
          Serial.print("X: ");
          Serial.print(myData.xData, 4);
          Serial.print(" Y: ");
          Serial.print(myData.yData, 4);
          Serial.print(" Z: ");
          Serial.print(myData.zData, 4);
          Serial.println();
        }
    */

    // We can read the data more quickly by calling getRawAccelBufferData because we know
    // the buffer is being used and what the data resolution is.
    // The default buffer resolution is 8-bit. It will be 16-bit because we called setBufferResolution above.
    // If you comment setBufferResolution, change the '1' to a '0' for 8-bit data.
    rawOutputData myRawData;
    if (kxAccel.getRawAccelBufferData(&myRawData, 1) == true) // Change the '1' to a '0' for 8-bit data.
    {
      kxAccel.convAccelData(&myData, &myRawData); // Manually convert the raw data to floating point
      Serial.print("X: ");
      Serial.print(myData.xData, 4);
      Serial.print(" Y: ");
      Serial.print(myData.yData, 4);
      Serial.print(" Z: ");
      Serial.print(myData.zData, 4);
      Serial.println();
    }
  }
  else
  {
    Serial.print("."); // If the data rate is 50Hz (default), we'll expect to see ~20 dots between samples
    delay(1);          // Wait 1ms
  }
}

Python test code:

import serial
import time

ser = serial.Serial("/dev/ttyUSB0", 115200)
count = 0

with open("dataFile.txt", "wb+") as f:
    t_end = time.time() + 10  # run 10 seconds
    while time.time() < t_end:
        line = ser.readline()
        f.write(line)
        count += 1
print("saved lines: %s" % count)

[delijati]

I tried the SPI interface, but unfortunately that seams to not work at least for me.

[1] https://forum.sparkfun.com/viewtopic.php?f=83&t=61461

[edspark]

Do you still need help @delijati? I see that you at least figured out SPI, but were you able to get the correct data output rate?

[delijati]

hi @edspark i currently get around 6kHz (x,y,z) as i'm sending the data via UDP to my PC. Will take a look into it the coming days to see what ODR i get on the ESP32.

[edspark]

Please reopen if you're still having problems, thanks @delijati !