I have a an app that needs to :
- read accelerometer data at 50Hz.
- aggregate 1minute of these readings
- verify if the sum of the standard deviations of x,y,and z is larger than a threshold.
- if yes, write the aggregated data into a file
- if not, empty the buffer and repeat.
The app runs normally during the day when I test it. It runs for hours no issues.
However, when I use it at night time, I noticed the app would last at most a couple of hours then it crashes.
Here are pieces of code I use, in hopes that someone can help me understand the issue.
This piece reads the accelerometer, aggregates the sum of standard deviations and the ts,x,y,z values.
startAccel() {
this.dataBufferView[this.bufferIndex++] = Int16Array.from(Date.now() - this.fitbitData.sessionDate)
//console.log("I am startAccel")
this.accelerometer.addEventListener("reading", () => {
this.ss = scientific.std(this.accelerometer.readings.x) + scientific.std(this.accelerometer.readings.y) + scientific.std(this.accelerometer.readings.z);
this.accelCumm.push(this.ss);
fileTimestamp = prevTimestamp = this.accelerometer.readings.timestamp[0]
const batchSize = this.accelerometer.readings.timestamp.lengthf
// let bufferIndex = 0, timestamp
//console.log(`ss=${this.ss}`)
//console.log(`timestamp[]=${accel.readings.timestamp}`)
for (let index = 0; index < batchSize; index++) {
//console.log(`${accel.readings.timestamp[index]} ${accel.readings.x[index]}}`)
// timestamp = this.accelerometer.readings.timestamp[index]
// this.dataBufferView[bufferIndex++] = timestamp - prevTimestamp // store differential timestamps so they fit in Int16
// prevTimestamp = timestamp
this.dataBufferView[this.bufferIndex++] = this.accelerometer.readings.x[index] * ACCEL_SCALAR
this.dataBufferView[this.bufferIndex++] = this.accelerometer.readings.y[index] * ACCEL_SCALAR
this.dataBufferView[this.bufferIndex++] = this.accelerometer.readings.z[index] * ACCEL_SCALAR
}
});
this.accelerometer.start();
}
This here is where I verify the max of the standard deviations and if it is higher than a threshold.
sendAccelInfo = () => {
fs.writeSync(this.file, this.dataBufferView);
// fs.closeSync(this.file);
let stats = fs.statSync('pippo.bin');
//vibration.start("ping");
displayText.text = `Size: ${stats.size} B`;
}
get_accelerometer = () => {
let maxActivity = 0;
for (let i = 0; i < this.accelCumm.length; i++) {
if (this.accelCumm[i] > maxActivity) {
maxActivity = this.accelCumm[i]
}
}
if (maxActivity >= this.maxIntesityThreshold) {
console.log(`Max=${maxActivity} is found..break`);
this.sendAccelInfo()
this.bufferIndex = 0;
this.accelCumm = [];
}
if (this.stopAccel) {
clearInterval(this.tid2);
fs.closeSync(this.file);
}
}
- the get_accelerometer function is called in a setInterval every 60 seconds.
- the binary file is open at the beginning of the app and closed when the app is closed in the morning. It is opened as
this.file = fs.openSync('pippo.bin', "w")
In my first testings, I thought the app would simply run out of memory since it has to keep 18kb of data for every minute but I tried running the app during the day for hours and it did not crash. Also if I understood correctly, there is a 4MB usable memory.
Unfortunately I am not very proficient with JS and I ran out of ideas on where I am getting it wrong. What also puzzles me is why does the app crashes at night when I go to sleep? Is it because of sleep monitoring running while also my app is running and thus my app, consuming a lot of memory is getting killed to give way to sleep monitoring?
my idea is to open and close the app everytime with append instead of opening it once and leaving it there.
Please let me know if you have any suggestions of what I might have been missing.