H3LIS331DL Output data rate

Sensors IMU & Motion
1

As the datasheet of H3LIS331DL has a 1000 Hz output data rate which means 1 reading every 1 millisecond, and that is what required in my project, I am using an I2C connection and the information from " https://learn.sparkfun.com/tutorials/h3 … -guide/all "and the period between two readings is 3 to 4 millisecond, the code is as follow :

#include "SparkFun_LIS331.h"
#include <Wire.h>

LIS331 xl;
unsigned long startMillis;  
unsigned long currentMillis;
void setup() 
{
  Wire.begin();
  xl.setI2CAddr(0x19);    // This MUST be called BEFORE .begin() so 

   //  .begin() can communicate with the chip
  xl.begin(LIS331::USE_I2C); // Selects the bus to be used and sets
                          //  the power up bit on the accelerometer.
                          //  Also zeroes out all accelerometer
                          //  registers that are user writable.
xl.axesEnable(true);

  xl.setPowerMode(LIS331::NORMAL);
  xl.setODR(LIS331::DR_1000HZ);
  
startMillis = millis();  //initial start time
  
  
  Serial.begin(115200);
  
}

void loop() 
{
  int16_t x, y, z;
   currentMillis = millis();
    xl.readAxes(x, y, z);  // The readAxes() function transfers the
 Serial.print(currentMillis - startMillis);Serial.print(",");

    Serial.print(xl.convertToG(100,x)); Serial.print(","); // The convertToG() function
    Serial.print(xl.convertToG(100,y)); Serial.print(","); // accepts as parameters the
    Serial.println(xl.convertToG(100,z)); // Serial.println(", ");// raw value and the current
  startMillis = currentMillis;
}

could you please help me in this regard.

Thanks

2

Have you calculated how long it takes to print all that data, every time through loop(), at about 10 characters per millisecond?

3

next to Jremington’s remark: which processor board do you use? Some board drivers add more overhead-time than others…

4

jremington , paulvha, thank you for your reply, actually I didn’t try for characters per milliseconds, but I have calculated only for the sensor output, I used Arduino Uno and wemos d1 mini and I had the same time for both

5

In your program, the total time between collecting successive sets of (X, Y, Z) data (the true output data rate) includes the time it takes to print the data.

6

Capture.JPG
it shows the total time between two readings, it is the output result of the code above,

Note: When I decrease the baud rate, the time between two readings will be increased ( more time between two readings ) but when I increase the baud rate the maximum time I had is 3 to 4 millisecond