Bangle.js: split up backlight on + screen unlock triggers, to allow some events to light the screen, others to unlock

[f8lxninja]

So for some reason the backlight will turn on when motion is detected, even though face up and twist are turned off. The only options I have it to turn on are BTN1 and touch. If I flick the watch repeatedly or move my arm in a consistent way the backlight turns on without even touching the screen or button.

If, however, you turn the wake on touch option off the issue goes away. Is this by design, or is it a limitation of how touch is perceived on the watch? I have a Kickstarter bangle 2 on 2v12.

[gfwilliams]

Hi,

This is by design. Basically we can't keep the touchscreen on all the time on Bangle.js 2 because it would flatten the battery in a few days, so to detect 'wake on touch' we use the accelerometer.

So it's actually detecting a physical 'tap' on the device, which is why flicking it turns the bangle on. When you trigger it by moving your arm, is it when you do a sharp movement? There are some settings to 'tune' the touch sensitivity but it's hard to get something that works in all cases.

Perhaps there should be a setting for 'wake on double-tap' which would a lot harder to do accidentally.

[f8lxninja]

Sometimes it is a sharp movement, other times it is not. One example is washing my hands. It is seemingly random when it decides that I had moved enough and turns the light on. Would it be possible to have an option to unlock the screen but do not wake the backlight if it detects movement? I have not found any settings to tune the touch sensitivity, only twist.

[gfwilliams]

What do you think about the double-tap idea?

Yes, sorry - the actual accelerometer setup isn't exposed via menus right now, but it could be done using the Bangle.accelWr command. I imagine there will always be some cases where it goes off accidentally, or it'll miss taps which would also be annoying.

Right now there isn't individual tuning of when to turn backlight on or unlock - but that could be added at some point

[f8lxninja]

Double tap could work, if you can configure the delay between taps. What I would like more is pressing the button wakes the touchscreen but only turns the light on when you start touching the display, and stays on for the delay that you set in the settings once you're done.

[gfwilliams]

The double-tap is handled by the accelerometer chip, so the delay can be configured, but again it's not super-pleasant to do.

It might be that one solution is just to create an app that lets you fine-tune the accelerometer's settings.

So I guess (and this has been asked before) the main issue is splitting the LCD backlight and LCD lock options up so you can choose what happens when.

Maybe wake on touch should go back to being based on touchscreen, and we need wake on tap and wake on double-tap

[f8lxninja]

I feel that's a good compromise. I am totally okay with it waking only on button press or some other means that is enabled in the settings.

[dmitrizagidulin]

Running into this as well, and fortunately happened on this issue, from search. I don't suppose it's on the roadmap?

Edit: Ah, never mind, I see there's a 'Wake on Twist' checkbox in Settings > LCD menu, so I just unchecked that.

[gfwilliams]

@dmitrizagidulin ok, so your issue was just the screen wakeups when you weren't expecting it?

I think on recent firmwares the default is for wake on twist to be off as well (before it was on).

[jonasborn]

I still think wake in touch could be a nice feature.
As for now, I can understand the power consumption issues, but isn't the TOUCH_PIN_IRQ already used, so having the CST816S in standby shouldn't take that much power? Might be totally wrong here, just started to explore the code base and the disassembly of the banglejs 2.

[gfwilliams]

We already use the IRQ pin to respond to touches - the handler is at https://github.com/espruino/Espruino/blob/master/libs/banglejs/jswrap_bangle.c#L1975-L2001

The issue was that there wasn't a bunch of publically available info on the touch controller, and what most people seemed to be doing at the time (including the original SMA Q3 firmware) was this: https://github.com/espruino/Espruino/blob/master/libs/banglejs/jswrap_bangle.c#L2875-L2885

Basically shutting it down when not needed and waking it up with reset. Because when running it used ~1.6mA all the time.

Looks like there's a bit more info now - eg https://github.com/fbiego/CST816S - so maybe there is a sleep mode you can use

You can write direct to the touch controller from JS with Bangle.touchWr so you could experiment, and if you can get it working such that it'll actually enter a sleep mode where it doesn't draw a bunch of power then I'd love to pull that functionality in (you may even just be able to expose it as an app)

[jonasborn]

Thanks, that's awesome to hear,
I am going to have a look at it and will inform it was successful. Thanks for the quick response

[gfwilliams]

Great! I should add that as far as I know the CST816S actually has its own firmware internally, so it's possible that the firmware installed on the ones in the Bangle doesn't support those extra features - but it's worth trying!

Actually measuring power usage can be a pain, but I have Bangles here where I've split them open to measure power usage - so if you get some commands that appear to work, let me know and I can tell you if they have any effect.