[Bangle.js 2] modification: add buzzer, bigger battery, more switches, minus HRM

@fanoush and @enaon, ha ha ha, I know. I will be careful. 😀
Thanks!

Nope! It didn't work. I guess I messed up something on the PCB somehow. Strange, I don't see anything wrong. hmmmm

Well, I disconnected the battery and reconnected, but it didn't solve the issue with the accelerometer. I think I have done all I could try. I don't want to damage other parts, so I will stop trying to figure it out. Although I'm going to miss the pedometer, but that's not a big deal.

My main reason to design the new case and adding so many (most people won't need it) buttons and buzzer and bigger battery was for my golfing (https://banglejs.com/apps/?id=golf-gps ). Currently it uses swipes for moving the holes and adding/subtracting scores while I'm playing, but if I touch (and slide) accidentally, the score or the hole changes unintentionally. That's why I wanted to have physical buttons (left/right and up/down) and bigger battery for continuous use of GPS. The buzzer is my preference over the vibration motor.

Although I lost the pedometer, I'm happy with the other modification. I have attached some pictures to show the internal arrangement of components in case someone's interested.

The motor is moved to the right side wall in a tightly fit hole. This motor vibrates radially, not axially, so it feels much stronger than original configuration (taped on the battery). The buzzer sounds loud enough. I have tested with a MOSFET and direct drive from the pin D43, but didn't see any difference, so just connected directly to the pin D43 for simplicity. As for the battery life, I tested yesterday with continuous GPS running after full charge and it lasted over 9 hours.

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That's awesome! Turning the motor on its side and fixing it to the case directly to amplify the buzz is something I could imagine to do in my next version as well since it is well cushioned/dampened when on the battery.

I opened my modified watch again to measure current for other reasons, and found the accelerometer was loose from the PCB. I gently touched it and was detached easily. During the modification, I haven’t touched that area with anything, especially the soldering iron.
Anyway, I’m trying to reattach it to see if I can get the accelerometer function again, but not successful yet.
But I noticed the number of pins on the package was different from the datasheet linked from the technical information page.
See attached screenshot of a part of the datasheet and a picture showing where the accelerometer used to be. In the datasheet, it’s 16 pins but the actual part has only 12 pins. Could anyone tell me what’s the actual part number? I want to see correct datasheet.

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That's a good point! I'm afraid I don't know what the exact part number is.

Looking at the PCB image you posted though, if you need to re-attach in the correct orientation the dot on the accelerometer case should be in the bottom left corner

In the same Technical information page, the I2C device list says it's Kionix KX022. I looked it up and found that was the correct part with 12 pins.
@Gordon, thank you for the tip of the orientation of the package. Since it's LGA package that all the pins are under the package and not exposed to the side, without take the PCB on a hot plate, it's almost impossible to re-attach it with only a solering iron. I tried with low temperature solering paste and heating the entire package with a large blob of solder, but couldn't solder it back properly. Unfortunately, one side of the package was damaged and I gave up. :-)

Argh, sorry to hear about your accelerometer. Thanks for the update though - I'll change the docs - I think KX023 was mentioned because that's what the Bangle.js 1 had and I forgot to update the file when moving over.

I can definitely recommend getting a heat gun - the chinese ones are pretty cheap and mine's been super helpful for this kind of thing.

We actually have some Bangles here that you might be interested in? for instance some where the SWD pins never worked so we couldn't program them. Most likely it's just an assembly fault and the board is OK, and as you're taking them to bits anyway it might be fine.

@Gordon, I found those parts on Aliexpress and ordered a couple of them already. Thank you for your offer though. Also I'm thinking to buy a hot air gun as well.
Thanks.

I'm thinking to buy a hot air gun as well

there are very cheap ones that don't even have temperature control nor air flow control, then the next level is something like this
https://www.aliexpress.com/item/4000525251154.html
I have it, it works, I used it few times without issues. It has three types of nozzles and turns automatically off when you put it into holder/stand and has both temperature and air flow control. It may not be professional for daily use, but for hobbyist it may be enough (=not sure about longevity of the heater element if used frequently). I got it 2 years ago for US $23.38 (with some aliexpress discount code).
EDIT: I see now it is cheaper from other sellers, e.g. https://www.aliexpress.com/item/1005002350207714.html

@fanoush, thank you very much for the information of the hot air gun with links. It looks good for my purposes.