⌚ Bangle.js 3 update

[gfwilliams]

We've been working on a Bangle.js 3 for a while now, and there have been little drips of information on this forum thread but I thought it was time to provide a more coherent update!

There will be a Bangle.js 3, likely shipping summer 2027. there will most likely be a pre-order again so I can get an idea of volumes for the initial production run, but only when I have mostly final pre production Bangles in my hands, so I'm confident on timescales.

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Highlights are:

• 1.2" 240x240, round, 64 colour screen (with compatibility for square Bangle.js 2 apps)
• 4 buttons (1 left, 3 right), and metal front bezel
• 128mhz ARM Cortex M33 (nRF54L15) with Bluetooth LE
• 2.4ghz WiFi via separate ESP32C2, capable of 2.4ghz SDR functionality
  *32mb flash memory
• Accelerometer, gyro and magnetometer
• Barometer and air temperature sensors
• Bosch smart gas sensor, allowing detection of specific smells
• Heart rate sensor
• Speaker, microphone and vibration motor
• Torch, and RGB indicator LED
• Infrared remote control transmitter and receiver
• Wireless charging
• 4 pin connector behind top strap allows charging, SWD programming, debug UART output, 2x analog-capable GPIO, as well as a switched 3v output!
• Non-glued, unscrewable rear case, with internal testpoints for available for adding custom hardware

Physically the watch takes the same straps and is the same height as the Bangle.js 2. It's very slightly thicker and wider, with a screen that's the same size diagonally as the Bangle.js 2, but which has extra width and height because it's round.

We have most hardware nailed down, CAD designs, and a development board set up and running apps:

Personally, I'm pretty excited. It's been a long time coming, but I've tried to take on board as many suggestions from the community as I can, and I feel like this should be a sensible every-day watch while still providing loads of cool features and plenty of scope for customisation.

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[ticalc-travis]

That is a really impressive feature set! Lots of things that will certainly be interesting to tinker with. But I wonder how that might impact the cost.

I've never designed UIs for a round screen before. It seems rather tricky. But with care I suppose it would allow for some useful extra screen space. Plus the extra physical buttons would reduce the need for on-screen buttons.

Overall, it looks really cool.

[gfwilliams]

It will end up costing a little more than the current Bangle, but not much. I've tried to add features where it's not too expensive to do so. The one feature that's still a question-mark is the BME690 sensor, which can 'fingerprint' and detect certain smells. If I can't source it nearer the time for a sensible price I may end up doing the normal Bangle.js 3 without it, and a 'pro' Bangle.js 3 with it.

The default menu and dialog box functionality is designed to work with the round screen, and there's a 'compatibility mode' where the old Bangle's 176x176 screen sits in the middle of the 240x240 circular screen, so mostly you shouldn't have to worry about dealing with the fact it's round unless you really want to stretch things out to fit.

[RKBoss6]

How would the compatibility mode work? Would it just show the specific app that needs it in the square part of the screen and still keep widgets at the top of the circle as shown in the picture, or would the entire screen basically convert to the rectangle as long as that app is loaded, where its effectively a bangle.js 2 screen on the watch?

[gfwilliams]

Right now I'm just putting everything in a square for simplicity, including widgets. Really the idea is just to get every existing app working on the new watch.

... But I think rather than going too far with compatibility modes we should be trying to make apps natively support the new screen as I think in most cases it'll be pretty easy - just shifting a few offsets - and the end result will be much better

[RKBoss6]

Yep, that's exactly what I was thinking too - more apps adjusted for it would be loads better for users and will look nicer on the round display too :)

[f-elle]

This really looks like something to get excited about! And it doesn't look like it will get too big for a round watch, which I do appreciate. Also I'm looking forward to hopefully be able to use the IR transmitter to switch off those annoying TVs in restaurants and bars.

[jeonlab]

All the features look amazing, but no GPS? I would like to have a GPS instead of the smell sensor which I doubt I would ever want use it.
Any plan to make a variant with a GPS?

[wminarik]

I'll add my disappointment about the lack of GPS, and I appreciate Gordon's reasons. No comments about the Bangle.js 2 GNSS, as it has been working fine! GNSS on the watch means I can leave my phone at home, rather than requiring the phone to make the watch work as I wish. The barometer (makes the GNSS more useful) and buttons probably means less water-resistance than for the Bangle.js 2, so the Bangle.js 3 seems to be more of a inside device that supplements an Android phone...

Can the GPIO on the 4-pin connector be used for I2C or UART to connect an external GNSS receiver?

[fanoush]

Can the GPIO on the 4-pin connector be used for I2C or UART to connect an external GNSS receiver?

that was the plan discussed in the other thread, and also once you get your shiny new watch you can also use old Bangle 2 as bluetooth GPS

[wminarik]

Using the Bangle2 as a bluetooth GNSS is clever! (I need to get caught up on the various threads...)
A wired connection is still useful, especially as I turn off BLE when running past Flock cameras.

[jeonlab]

So this will be how you get the GPS data on a new watch.

[fanoush]

Actually I have small nrf52 based fitness tracker running Espruino with this exact gps chip, so I was thinking I would strap it to something I wear when running, if my watch would not have gps, but same can be done with Bangle 2 if you stop using it as your main watch

[halemmerich]

I like this design a lot! How are you fitting the bottom straight edge of the display in there? Seems pretty tight. Do you have some dimensions for the case? Thickness and diameter of the main body?
Can you share some details on water resistance measures? I'm mainly interested in how the buttons will try to keep water out, since that was a weak point on the v2 after sealing up the barometer hole. I suspect you won't be going for an IP-rating as the tests are expensive.
No swimming resistance needed for me but no babying of the watch during heavy rain would be nice.
As a side note: I have Creative bone conduction headphones, those actually come with a silicone plug for the mic hole to make them usable during swimming 😂

[gfwilliams]

Yes, I think it's quite tight, but there is a small black border on the LCD too - it was just unavoidable. The touchscreen glass there (which is what you actualy see in the picture) may not be final. Someone asked and I posted a 3D model at https://github.com/orgs/espruino/discussions/7341#discussioncomment-18757091 so you can check dimensions there if you want.

On button sealing, it was something in particular I pushed the manufacturer about, and they assure me that it's good. The speaker will be sealed into the case so water ingress there isn't a big deal, but the weak point will be the opening for the microphone and barometer/smell sensor, which will have a waterproof membrane. It is possible that a rubber plug (or even a screw) could be added, I'll enquire.

But in general it's as you say: I wouldn't advise swimming, but washing hands, quick submersion (eg reaching into water), and heavy rain should all be absolutely fine.

[banglejsdev]

Thank you! This is looking very promising and has me excited about updating my apps to run on Bangle 3. And to that end, I would like to ask:

1. How much RAM will it have?
2. Does a 240x240 rounded display mean that all 240x240 pixels fit entirely within the physical circular display (in which case the edges of the screen are unusable), or that the entire physical circular display fits within the 240x240 area (in which case pixels outside the circumference of the circle are unusable)?
3. What will the capacity of the battery be?

Thank you in advance for replying whenever it's convenient for you and best of luck on Bangle 3, I can't wait!

[halemmerich]

1. 256KB (see nRF54L15)
2. The edges of the 240x240 virtual square are not usable. the 176x176 pixel Bangle.js 2 screen will fit almost completely pixel for pixel in the center. There should be about 20 Pixels of area or a ~7x7 triangle lost in each corner of that square.
3. I don't know, but I suspect a little bit more than the Bangle.js 2 because of a more space in the case (and 100% less GPS aerial). About 250mAh is my guess.

[fanoush]

3. What will the capacity of the battery be?

this won't tell you much when you don't know what the power consumption of the device and its various parts is - one example - the nrf54L15 CPU running at 128MHz draws less than nrf52840 at 64Mhz (=Bangle.js 2) so running same amount of code draws ~60% less power, the BLE radio is more efficient too, check tables here
https://academy.nordicsemi.com/courses/nrf54l-series-express-course/lessons/lesson-1-architecture-overview/topic/processing-performance-and-power-consumption/
so even on same battery it may last longer, but of course it also depends on usage and power draw of other parts like the display

[gfwilliams]

The battery will be much the same - around 200mAh. You'd think there might be more room in the case, but because there's a speaker it actually takes a big chunk of what's available.

However because the back can be unscrewed and I'll be releasing CAD files for a 'deeper' back, I'd be pretty sure that at some point someone's going to fit a much bigger battery.

And yes, on the screen it's a 240x240 buffer but the corners are not visible. While it's a shame to waste that data, it does make scrolling much easier as when you scroll, data that was offscreen can be scrolled on and doesn't have to be re-rendered.

[Techbrology]

so the bangle js 2 screen is fairly bright with backlight to me, which is good. will the 3 be brighter or less brighter or the same?

[gfwilliams]

I think it might be a little brighter, but I haven't tested them side by side yet I'm afraid.

[fanoush]

• 2.4ghz WiFi via separate ESP32C2, capable of 2.4ghz SDR functionality

@gfwilliams if there is space on PCB the ESP32 chips actually can do relatively low power BLE and Wifi in light sleep when there is external 32kHz crystal populated. Typical ESP32 devboards do not populate it as people do not care but the numbers are here https://github.com/espressif/esp-idf/blob/master/examples/bluetooth/nimble/power_save/README.md#typical-current-consumption-with-management-enabled

C2 is not the best of them but still good. According to https://docs.espressif.com/projects/esp-idf/en/stable/esp32c2/api-reference/system/sleep_modes.html#wi-fi-bluetooth-and-sleep-modes it could maintain wifi connection while being in this light sleep when properly configured.

EDIT: oh, unlike other ESP32 variants like C3 or S3 the C2 does not accept typical crystal with two pins and capacitors but it needs 32kHz signal on GPIO0 https://docs.espressif.com/projects/esp-idf/en/v5.1/esp32c2/api-reference/system/system_time.html#rtc-timer-clock-sources "External 32 kHz oscillator at GPIO0 pin: Allows using 32 kHz clock generated by an external circuit. The external clock signal must be connected to the GPIO0 pin. The amplitude should be less than 1.2 V for sine wave signal and less than 1 V for square wave signal. Common mode voltage should be in the range of 0.1 < Vcm < 0.5xVamp, where Vamp stands for signal amplitude. " so not sure what can generate such signal but looks like typical crystal is not needed EDIT2: google says SiTime SiT1532 is tiny and can do this

[gfwilliams]

Wow, that's neat! Although the C2 looks like it doesn't directly contain a 32kHz crystal driver, so it has to be fed by an external 1V clock source on GPIO0 - and while I have one pin on the nRF54 which is set to be brought out to the HRM board to allow for extra things to be added, I'm not sure it really makes sense to add a potential divider and connect it up.

[jeonlab]

With a deep sleep mode, the ESP32 draws relatively low current, but as soon as you turn on the WiFi, it becomes a battery killer. I don't really think I would ever want to use WiFi or SDR on a watch.
I know a GPS is out of scope now and I'm sorry to bring this up again, but as a huge fan of a GPS capability and its usefulness, I wonder if I can replace the ESP32 with a GPS module later. Would that be too risky to damage the board and fail to connect pins for the GPS module? Just a thought.

[halemmerich]

I guess replacing the ESP32 with a GPS module in place is close to impossible. You would need to find one that has the same footprint and well enough matching pinout to not be destroyed AND have enough connections to work. Then you would need to find space for the antenna and somehow connect gps module and antenna and have the antenna somewhere where it can work correctly. The connection between those alone will probably be impossible in the available space. The Bangle.js 2 had a pretty big antenna (close to full width and about 4x5mm across) for the case size and that works pretty mediocre. Your best bet will probably be an external module on the strap. You are looking at something like 19x19x3mm for a good enough working module including antenna.

[pavelmachek]

That will be fun piece of hardware :-). Three CPUs, one ARM and 2x RISC-V, AFAICT.

I like my Bangle.js2, but if it breaks, I'll need a replacement. I could easily live w/o smell sensor and IR RX/TX. I could probably live w/o ESP32 as well, especially if it meant lighter / cheaper hw or better battery life.

[fanoush]

Three CPUs, one ARM and 2x RISC-V, AFAICT.

that would be too easy, there is one more - PY32F040 https://github.com/espruino/Espruino/tree/master/libs/banglejs/banglejs3_py32

[pavelmachek]

Ok, so at least 2x ARM + 2x RISC-V. Fun :-). I guess there will be other tiny CPUs hidden around. This will be fun to program :-).