Espruino on your watch!

Wow @fanoush, thank you very much!

Just ask if something is not clear. The https://www.youtube.com/watch?v=LDGxU-i7z7U
video and the D6 flasher was done by Aaron Christophel http://atcnetz.blogspot.com/ It really helps to make it easier for newbies. Btw as it uses slightly modified Nordic DFU library (with added DFU GUIDs used by Desay bootloader) it also works with secure bootloader used with SDK12 and up. So the same D6 flasher app can be used when e.g. switching between SDK11 based stock firmware or Espruino, SDK12 based Espruino and also SDK15 based micropython with adafruit bootloader - each using different bootloader and DFU service GUIDs.

As for HX03W I will upload somewhere DFU package for original Lenovo firmware app so you could recover from Espruino back to original state. Well almost, there is also one flash page at 0x74000 with lenovo specific serial number which is also printed on the box. If this page gets cleared the serial changes to 1234567890 or something but it doesn't matter. In theory you could try to backup it from Espruino via Flash module before it gets overwritten if it bothers you. Or it can be recreated later according to numbers printed on the box.

@MaBe
HX03W build for current version is here https://github.com/fanoush/ds-d6/tree/master/espruino/DFU/HX03W I have verified it in my device. As mentioned the only difference from DS-D6 build is bluetooth name and also value of process.env.BOARD which is shown when connected via Espruino IDE.

Restore package of Lenovo fitness app is here https://github.com/fanoush/ds-d6/blob/master/fwdump/HX03W_1.0.0.zip

and BTW when using D6 flasher make sure you select the zip file, on my phone I need to touch and hold the zip to select it otherwise it opens the zip and shows file inside it to select

Great, thanks @fanoush

I have some experience with flashing PuckJS ;-)

DS-D6 is now for $4.99 :-)

@fanoush I have Makibes m3 smartwatch and it has dual system and one is nrf52840,I would like to make a custom firmware for it,can you help me out? And can you provide me the firmware of cavosmart v12

another interesting nrf52382 watch DT28, FCC ID photos firmware here. The firmware looks signed but there are screws so it looks like it can be opened and closed relatively easily (SWD touch points on the other side of the board). No gps, not 52840 but looks nice and has full touchscreen, big battery and two buttons and is relatively cheap so might be interesting for someone.

And btw looks another $4.99 DS-D6 deal is coming on gearbest in few hours (which is on the other hand only $1 cheaper than 'normal' price with MPOWDS-D6 promo code entered at checkout anytime, so not that big deal)

Not sure if it it is worth mentioning but banggood has $14.99 deal for HX03W now. Not $9.99 like before but still slightly cheaper than normal price.

A story on Hackaday with regard to flashing Arduino on watches: https://hackaday.com/2019/08/23/ota-flash-tool-makes-fitness-tracker-hacking-more-accessible/

Just FYI, there is new "Da Fit app' set of nrf52832 smartwatches that are hackable without taking apart. See this video made by atc1441 https://www.youtube.com/watch?v=n-ZMQaasfAo
for more details. The easy flashing procedure is currently in progress but the concept appears to work including reflashing its custom bootloader with nordic one.

Just beware that Da Fit app support watches with multiple CPUs so not all of them are automatically nrf52832. Randoms tips: rectangular with full touch screen P8 (in the video), or with full circular display SN80, CF98, F13 (like this one, not the other one), also the CV16 is quite unusual with dual display.

A week ago I have ordered P8 on aliexpress so it will take some time to arrive to verify the procedure with real device by myself, but there already is lot of things to do before it arrives. I am also thinking a bit about CF98 since from reviews and listings it looks like it is a bit smaller - only 4.1cm diameter unlike F18, DT28 or SN80 which is 5cm.

BTW, looks like all of the watches have external SPI flash as the firmware update procedure depends on it (the stock app receives the firmware from Da Fit app, writes it to SPI, then reboots to bootloader which upgrades the app from SPI with no bluetooth DFU involved).