Nano BLE Sense Rev2 IMU sampling rate

Official Hardware Nano Family Nano 33 BLE Sense
1

Dear everyone,

I just started to work on Sense Rev2 with the official library.
I successfully change the sample rate by editing the 228 lines of the src/BMI270.cpp.
In the serial monitor, the sample rate is indeed close to 1600Hz.

However, I can't access data in real 1600Hz on my PC via Serial communication. The sample rate is only 180+Hz.
Based on my previous experience, my serial communication code is correct.
Can you point out what else I should do now?
Thanks for your help!

/*
  Arduino BMI270 - Simple Accelerometer

  This example reads the acceleration values from the BMI270
  sensor and continuously prints them to the Serial Monitor
  or Serial Plotter.

  The circuit:
  - Arduino Nano 33 BLE Sense Rev2

  created 10 Jul 2019
  by Riccardo Rizzo

  This example code is in the public domain.
*/

#include "Arduino_BMI270_BMM150.h"

uint8_t sampleBuffer_8bit[192];
int sb_index = 0;
short x, y, z;

void setup() {
  Serial.begin(115200);
  while (!Serial);
  Serial.println("Started");

  if (!IMU.begin()) {
    Serial.println("Failed to initialize IMU!");
    while (1);
  }

  Serial.print("Accelerometer sample rate = ");
  Serial.print(IMU.accelerationSampleRate());
  Serial.println(" Hz");
}

void loop() {
  if (IMU.accelerationAvailable()) {
    IMU.readRawAcceleration(x, y, z);

    // Serial.print(x);
    // Serial.print('\t');
    // Serial.print(y);
    // Serial.print('\t');
    // Serial.println(z);
    
    sampleBuffer_8bit[sb_index] = (x & 0xFF);
    sb_index ++;
    sampleBuffer_8bit[sb_index] = (x >> 8) & 0xFF;
    sb_index ++;
    
    if (sb_index >= 192){
        Serial.write(sampleBuffer_8bit, sb_index);
        sb_index=0;
        }   
  }
}

Edit:
I change to 200Hz config, the real sample rate is 190Hz, however, when I go to 400Hz, it is still 200Hz. Since the available() is achieved by interrupt, I am confused where is the bottleneck of it.

Efficiently reading all 3 IMU sensors in Nano 33 BLE Sense Rev.2
2

The data transfer rate between the sensor and the Arduino might be a bottleneck.

3

Dear everyone,

I finally made it, I literally reproduce the minimal get started for BMI270.
I attach the ino file as well as the config file as follows. The key to success is loading the config. There are also some other tricks.
bmi270.h (50.4 KB)
bmi270.ino (3.6 KB)

By the way, I still have no idea why the official library is limited to 200Hz (the code looks pretty correct). As pointed out by @jremington , maybe I will look at increasing the Wire speed in the official library.

4

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