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Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
@fanoush
There is another nRF52840 watch. I was going through 60 FW links from H Band android app (credit goes again to the same guy) and most is nrf51, some is nrf52 - all nrf52 are SDK12, signed and one has stack pointer 0x20037404 so looks like 256KB SRAM. nrfutil says it is hw version 52 however the soft device is recent with app start at 0x26000 (same as ID205 above, sdk12 SoftDevice 3.0 has 0x1f000). The string found in firmware that may be device name is V12 which may be this
https://wosmart.en.alibaba.com/product/60829664160-807772971/FITUP_smart_watch_bracelet_V12_sport_fitness_tracker_nRF52840_smart_bracelet.html and possibly also https://www.cavosmart.com/products/fitness-tracker-v12/
Again the firmware is signed so this is just if one wants to take it apart.
EDIT: this one is a bit risky to get for the 52840 chip, there are two same/similar devices V12 and V12C. The V12C one has older nrf52 chip. If you check this page in chinese and translate to english http://www.wo-smart.com/p-333.html then it is very confusing what is the difference and which one is better/newer but they do mention different chips. I also found V12C FW binary and this one is indeed SDK12 based with <64K SRAM stack pointer.