Reverse Engineering Smart Wristband LM707

Recently bought a couple of "Smart bracelets"  LM707

to try RE so that I can put my own Firmware.
They have some nice features such as:
1. Color IPS LCD 80x160
2. Accelerometer
3. Pulse sensor
4. fast CPU...
5. BLE
6. Motor

I read some of articles about this and they usually have a NRF51/52 micro with BLE.
Sometimes they have the TLRS8266 by Telink.
So I thought get one open it up, see whats inside, *RE*, profit!

Got mine, opened it up and this what I got.

That weird chip is the MCU with markings 05PUN2 and a date code, and nothing else.

I had no idea what type of micro that is (still don't).

I've RE the APK that comes with it (luckily it was not protected), the app supports different types of 

MCUs (about 49 models), some are based on TELINK MCUs there are a mentions in the code.

and something called MAXSCEND, and this is what it's based on. 

No SDK no Datasheets, not info whatsoever, I have a method of uploading Firmware over OTP

(D/L of all the firmwares from the site). but they are of unknown Architecture so no idea.

I'm stuck, if anybody has any info, write in comments.

R.

ESP8266 GameBoy Emulator, attempt.

I had an idea, to port a GameBoy emulator to an ESP8266 with an LCD screen.
found a good candidate for porting Peanut-GB, it's only a single file (.H) and with
plenty of examples.

Very little setup required and a single lcd_draw_line callback, implement LCD drawing
there and voila, GB emulator on the ESP8266 (node MCU clone), but it seems
the raw power of C is not sufficient for this task, and the LCD library
that I've chosen (TFT_eSPI) and modified was also insufficient to make
the emulator run at adequate speeds.

Games are stored in the flash using bin2hex.

The LCD in use is ST7789 based 240x240 connected to the SPI bus running at 40 Mhz.

Pinout:
NodeMCU - LCD
GND -> GND
3.3V -> VCC
3.3V -> BLK
D3 -> DC
D4 -> RES
D5 -> SCL
D7 -> SDA

So what do we have:
1. The emulator runs, tried with "super mario land", Tetris and a demo.
2. Uhm... Profit ?

What we don't have.
1. Good frame time, each frame takes between 70~200 ms which translates between 14~5 FPS.
2. Audio (There was not enough time for smooth frame rates.. so ...)
3. Key input (Yeah.. no..)


It seems that no matter how hard I tried to optimize the code the drawing part
would always lag, if we remove the LCD part, the core did have enough
time to emulate the game, but I think an emulator without a screen
is not a good emulator :)

What did I try to do:
1. ESP runs at 160 MHz, I can try to use NO_SDK (run at 340 Mhz) by CNLohr but the SPI bus is        affected by it.
2. Optimize the gb_draw_line up the wazoo, replaced all multiplications with right shifts.
3. Added per line hash drawing capabilities, so if the pixels of the line did not change, don;t draw            them, helpful with static games, not so much with scrolling.
4. Moving the game code to DRAM, did not produce significant speed ups. *
5. DynaRec? will probably require a lot of RAM and we have only 32000 bytes left.

* One of the issues that I've encountered is that the game needs to reside on the flash,  but because of alignment issues (the game is a an array of bytes [8-bit] but the memory of the ESP is 32Bit) the reading is slower.

Everything was developed using Sloeber, highly recommended for Android development.
Sources: primary project.
Sources: TFT_eSPI modified library
Hope that helps anybody.

R.