Puck.js IMU data logging

Hello,

I would like to log some IMU data using my Puck.js v.2.

I have set up a SD card reader (w/ SPI HW set to 8Mbps) on it so I can log the data. I can log the data at maximum 160Hz in average which is quite low for what I would like to do. I guess there are a lot of "wasted" time when converting the JSON object to string, and then when writing the data to the file. Note, I am using "Stream File IO".

I am far from being an expert, but maybe some on this forum could help me to know how much I can expect from the device. If I were to write my own C code to log the data from the IMU directly to the SD card, what would be the possible maximum sampling rate for instance?

(My messy code below)

function onInit(){
  // Wire up up MOSI, MISO, SCK and CS pins (along with 3.3v and GND)
SPI1.setup({mosi:D30, miso:D28, sck:D29, baud: 8000000});
// console.log(E);
E.connectSDCard(SPI1, D31 /*CS*/);
// see what's on the device
  try {
    console.log(require("fs").readdirSync());
  } catch(error){
    console.log(error);
  }
}

var data = [];
var i = 0;
// Store data into filesystem
function storeMyData(fID, start, a) {  
  if (i>100) {
    i = 0;
    var t = new Date.now();
    fID.write(data);
    console.log((new Date.now()) - t);
    data = [];
  } else {
    data += (Date.now()-start) + "," + 
            a.acc.x + "," +
            a.acc.y + "," +
            a.acc.z + "," +
            a.gyro.x + "," +
            a.gyro.y + "," +
            a.gyro.z + "\n"; 
  } 
  i++;
}

function openFile(){
  var start = Date.now();
  var fID = E.openFile("data"+start+".csv", "w");
  fID.write("Time (ms), "+
            "acc X, "+
            "acc Y, "+
            "acc Z, "+
            "gyro X, "+
            "gyro Y, "+
            "gyro Z \n");
  return {fID: fID, start: start};
}

onInit();
var res = openFile();
var fID = res.fID;
const start = res.start;

function onButton(e){
  d = e.time - e.lastTime;
  if (d>0.5) {
    digitalPulse(LED2, 1, [100, 100, 100]);
    Puck.accelOn(208);
    Puck.on('accel', function(a) {
      storeMyData(fID, start, a);      
    });
  } else {    
    try {
      Puck.accelOff();
      fID.close();
      console.log("stopped!");
      digitalPulse(LED1, 1, [100, 100, 100]);
    } catch(error) {
      console.log(error);
    }    
  }
}

Thanks in advance,

Greetings