Bangle.js 2 backlight randomly turns on.

I have wake on twist and wake on faceup disabled yet the backlight keeps turning on seemingly random, didn't see any other setting for this anywhere, any help?

Firmware: 2v19
Boot: v0.59
Settings: v0.68

Do you have tap unlock via the 'Light Switch' widget? Or another non standard way to unlock by tap or twist?

This has shown to be happening when tap/twist unlock is active in some way and HRM is capturing a reading.

See:

• https://forum.espruino.com/conversations/391667/#17188718 (specifically that comment, but also the whole conversation)
  
• and https://forum.espruino.com/conversations/390041/
  

I don't think i have anything that unlocks the screen installed and HRM interval is set to off, these are my installed apps:

widlock (0.08), widalarm (0.01), widbatpc (0.19), about (0.14), alarm (0.46), files (0.08), gpsinfo (0.12), health (0.28), hrm (0.11), info (0.03), locale (0.17), notify (0.13), rebble (0.16), sched (0.22), setting (0.68), widdevst (0.03), widcloselaunch (0.02), gpsautotime (0.04), altimeter (0.04), boot (0.59), chance (0.01), clock_info (0.07), counter (0.04), dtlaunch (0.24), mylocation (0.10), magnav (0.06), smpltmr (0.08), menuwheel (0.02)

Disabled wake on tap and it doesnt happen, also i can reliably reproduce it by shaking it horizontally (holding it by the straps), so it seems to be related to the accelerometer and wake on tap.

Ok, I don't really expect there to be anything there. But just in case. If you connect to the Espruino Web IDE and trigger the behavior, do you see anything printed in the console window on the left hand side?

Edit: Also, maybe try doing a settings rewrite in 'Settings'->'Utils'

it seems to be related to the accelerometer and wake on tap.

Ok - definitely try and update to a 'cutting edge' build then, and this will likely be fixed. I tweaked some settings about a month ago to make the accelerometer less susceptible to this (it gets worse when the HRM is enabled).

I would have released a 2v20 release by now but honestly I don't want a bunch of people getting their Bangles at Christmas and immediately updating and perhaps having problems when I'm not around to help out :)

@Ganblejs Nothing in the IDE console, and it keeps happening after a settings rewrite.

@Gordon tried the cutting edge build (2v19.106 according to the console) and now for it to happen i need to shake it harder and/or longer, also seems to happen less frequently under nomal usage, still happens tho, is there no way to disable or not use the accelerometer for wake on tap?

Thanks for checking with the Web IDE.

is there no way to disable or not use the accelerometer for wake on tap?

It's technically not impossible to tweak code to make that happen. But as the README of the settings app says:

• Wake on X should the given activity wake up the Bangle.js LCD?
  
  • On Bangle.js 2 when locked the touchscreen is turned off to save power. Because of this, Wake on Touch actually uses the accelerometer, and you need to actually tap the display to wake Bangle.js (we recently renamed the menu item to Wake on Tap).
    

The accel increase due to HRM can be anywhere between 1.5x -> 15x . Thats why increasing threshold does not eliminate it completely but you can increase the threshold further ::

//bit is changed to update settings
var c = Bangle.accelRd(0x18); // CNTL1
Bangle.accelWr(0x18, c &~0x80);
//adjust threshold, where 0x25 is the threshold value (increase/decrease)
Bangle.accelWr(0x27, 0x25);
//restore
Bangle.accelWr(0x18, c);

0x25 is hex, so 0x20 is lower, 0x30 is higher