LSM9DS1 breakout - How to increase speed

Question

With regards to the Adafruit LSM9DS1 breakout: enter link description here

And using the Library: enter link description here

I am trying to increase the sample rate, or speed of this chip. I am using a Sparkfun Pro Micro 5V

With the adafruit library, you need to request accelerometer, gyro, magnetometer and temperature at once, and all I need is the accelerometer values. I am hoping by figuring out how to request only the accel values it will speed up the loop. But also, there must be another setting that could speed up the sample rate?

Any help would be appreciated!

my code currently:

#include <Wire.h>
#include <SPI.h>
#include <Adafruit_LSM9DS1.h>
#include <Adafruit_Sensor.h>  // not used in this demo but required!
Adafruit_LSM9DS1 lsm = Adafruit_LSM9DS1();
#define LSM9DS1_SCK A5
#define LSM9DS1_MISO 12
#define LSM9DS1_MOSI A4
#define LSM9DS1_XGCS 6
#define LSM9DS1_MCS 5

void setupSensor()
{
  // 1.) Set the accelerometer range
  lsm.setupAccel(lsm.LSM9DS1_ACCELRANGE_2G);
  //lsm.setupAccel(lsm.LSM9DS1_ACCELRANGE_4G);
  //lsm.setupAccel(lsm.LSM9DS1_ACCELRANGE_8G);
  //lsm.setupAccel(lsm.LSM9DS1_ACCELRANGE_16G);

  // 2.) Set the magnetometer sensitivity
  lsm.setupMag(lsm.LSM9DS1_MAGGAIN_4GAUSS);
  //lsm.setupMag(lsm.LSM9DS1_MAGGAIN_8GAUSS);
  //lsm.setupMag(lsm.LSM9DS1_MAGGAIN_12GAUSS);
  //lsm.setupMag(lsm.LSM9DS1_MAGGAIN_16GAUSS);

  // 3.) Setup the gyroscope
  lsm.setupGyro(lsm.LSM9DS1_GYROSCALE_245DPS);
  //lsm.setupGyro(lsm.LSM9DS1_GYROSCALE_500DPS);
  //lsm.setupGyro(lsm.LSM9DS1_GYROSCALE_2000DPS);
}

double accelX = 0;
double accelY = 0;
double accelZ = 0;
double rms = 0;

void setup() 
{
  Serial.begin(115200);
  // Try to initialize and warn if we couldn't detect the chip
  if (!lsm.begin())
  {
    Serial.println("Oops ... unable to initialize the LSM9DS1. Check your 
wiring!");
    while (1);
  }
  Serial.println("Found LSM9DS1 9DOF");
  setupSensor();
  delay(5000);//program stabilization
}

void loop() 
{
  lsm.read();
  sensors_event_t a, m, g, temp;
  lsm.getEvent(&a, &m, &g, &temp); 
  accelX = a.acceleration.x;
  accelY = a.acceleration.y;
  accelZ = a.acceleration.z;
  rms = (accelX*accelX)+(accelY*accelY)+(accelZ*accelZ);
  Serial.println(rms);
}

Answer 1

Check the header of the library,

you will find readAccel readMag readGyro and readTemp in separate public functions and looking at the implementation of read it just calls those 4 in sequence. readAccel will update the accelData member field.

So you can just call lsm.readAccel() in the loop and then grab lsm.accelData directly and ignore the rest.

void loop() 
{
  lsm.readAccel();
  accelX = lsm.accelData.x;
  accelY = lsm.accelData.y;
  accelZ = lsm.accelData.z;
  rms = (accelX*accelX)+(accelY*accelY)+(accelZ*accelZ);
  Serial.println(rms);
}

Answer 2

Here is a link to the LSM9DS1 datasheet. In Chapter 3 it describes how to put the device in Accelerometer-only mode. At a quick scan of it, I believe there was timing information also, but at least knowing how to do it, you could then make your own timing measurements.