Simple Accelerometer build

[espruino-discuss]

Posted at 2023-04-21 by user155236

Hello,
I am using the Puck.js to just collect accelerometer data over a period of time. So far, I have built some code to collect and store the accelerometer data until the button is pushed. However, the memory is full after just a couple sections, and I am aiming to store accelerometer data over nearly an hour.

I also want the data to be stored in a csv, ideally a simple downloadable file. I feel like there has to be a way to store the data as it comes in on a separate file, and then delete it off the memory to keep that space open, but I can't find anything about that. Any suggestions?

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Attachments:

• code.js

[espruino-discuss]

Posted at 2023-04-21 by user155236

As an additional note, this is in conjuction with data we collect at 250 Hz, while this data is not as significant to need that high of a sampling frequency, at least 1 datapoint per second would be necessary.

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Posted at 2023-04-21 by @gfwilliams

It might be worth looking at http://www.espruino.com/Data+Collection#flash-memory for how to store data in flash memory vs RAM. It also comes with an example of how to output the data as CSV.

If you write a 'minimal' Puck.js build to your Puck (https://www.espruino.com/Download#puckjs) you get more free flash memory - I think around 90kB.

So if you write accelerometer data as 16 bit values so you don't lose any information that's 6 bytes per reading, so 15,000 samples - and there are only 3600 seconds in an hour.

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Posted at 2023-04-21 by @gfwilliams

Actually, I should add, that example stores the data as a string - and to get the maximum data in there you want in binary.

So instead of:

saveData(getTime()+","+E.getTemperature()+"\n");

you probably want:

saveData((new Uint16Array([acc.x, acc.y, acc.z])).buffer);