Pedometer count issue and question

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•

Rudi
Hi there!
I've also been experimenting with pedometer accuracy and would like to share my results.
I'm using several parameters - currently just as constants in the JS code:
```
// Max step duration (ms)
const cMaxTime = 1200;
// Min step duration (ms)
const cMinTime = 240;
// Max difference between consecutive steps (%)
const cMaxDiff = 50;
// Min number of consecutive steps
const cMinSteps = 5;
// Step sensitivity as per http://forum.espruino.com/comments/15186837/
const cSensitivity = 400;
```
The trouble I'm running into is that getTime() seems to have a resolution of 80ms, which gives me trouble with really quick steps. When two steps are only 200ms apart, the jitter will often exceed the 50% set in cMaxDiff. Since I'm not a terriffic runner, that is not a problem for me, but for some it might be.

Maybe you would like to look into my code and use the best from both our attempts.

Thanks a lot!

1 Attachment
- pedotest.js

•

Robin in reply to @Rudi

Sun 2020.04.05

post #14 'The trouble I'm running into is that getTime() seems to have a resolution of 80ms'

Hi @Rudi, just ran some tests fetching the getTime() value from within an interval. From 100msec, 10msec, 1msec it can be seen that the call returns a value extremely close to that which is expected, even with a small interpreter execution duration.

dur = 100
  time at [ 1 ]  85118.3  9614868164  diff: 0.0  9997558593
  time at [ 2 ]  85118.4  9612426757  diff: 0.1  0003662109
  time at [ 3 ]  85118.5  9616088867  diff: 0.1  0000610351

dur = 10
  time at [ 1 ]  84861.25  775146484  diff: 0.00  997924804
  time at [ 2 ]  84861.26  773071289  diff: 0.01  004028320
  time at [ 3 ]  84861.27  777099609  diff: 0.00  994873046

dur = 1
  time at [ 1 ]  84824.128  57055664  diff: 0.000  9765625
  time at [ 2 ]  84824.129  54711914  diff: 0.000  94604492
  time at [ 3 ]  84824.130  49316406  diff: 0.000  9765625

raw data with visual spacing remeoved

dur = 100
  time at [ 1 ]  85118.39614868164  diff: 0.09997558593
  time at [ 2 ]  85118.49612426757  diff: 0.10003662109
  time at [ 3 ]  85118.59616088867  diff: 0.10000610351

dur = 10
  time at [ 1 ]  84861.25775146484  diff: 0.00997924804
  time at [ 2 ]  84861.26773071289  diff: 0.01004028320
  time at [ 3 ]  84861.27777099609  diff: 0.00994873046

dur = 1
  time at [ 1 ]  84824.12857055664  diff: 0.0009765625
  time at [ 2 ]  84824.12954711914  diff: 0.00094604492
  time at [ 3 ]  84824.13049316406  diff: 0.0009765625

Checked the source for acceleration thresholds?

https://github.com/espruino/Espruino/blob/master/libs/banglejs/jswrap_bangle.c#L90
https://github.com/espruino/Espruino/blob/master/libs/banglejs/jswrap_bangle.c#L366

It's more likely to be the print() statements scattered throughout.

Pedometer count issue and question

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