Android App, Firmware and Circuit for a DIY Smartwatch working with Bluetooth Low Energy (4.x)
Features:
- Press Button 1.5 s : sync the time between watch and phone. Show date and notifications as scrolling chars.
- Press Button 0.5 s : show the time calculated by the watch. Show the battery level and an analog clock
- small analog clock
- digital clock
- Battery Level
- about 18 hours with LiPo 3.7V (170mA)
- some emoticons works
- transmit more than 20 bytes
The DIY smartwatch shows a calculated time without a connection to your phone. This time is a bit faster to pretent problems. It is about 1 second in 6 hours.
Support me: 
Get a PDF (german) about my UART Smartwatch Project from here:
or as Website
UART-Smartwatch APK or get the App from f-Droid
It is strange, but Bluetooth Low Energy with Android 6 needs Location access to search for BLE devices.
This App needs access to all notifications. You have to add these access in the preferences of your Smartphone:
Devices:
- Adafruit Bluefruit LE UART Friend
- Micro OLED Breakout
- Pro Trinket 3V
- LiPo 3,7V (170mAh)
In stuff/ is a small c program to make you own Smartwatch startup logo:
- make a 64x48 s/w Image
- store it as xbm file (e.g. with Gimp) without x10 option
- copy the content into the code
- compile and execute the code
- copy the printed output
- open: Arduino/libraries/Micro_OLED_Breakout/src/SFE_MicroOLED.cpp
- paste it into / replace the hex-chars of
static uint8_t screenmemory [] = {...} - rebuild the UART-Smartwatch Firmware with Arduino IDE
- make the aggressive message getting (rev 3.1) as an option, because the downcounting (how many unread messages) does not work with that
- better "down and upcounting" to fix the above problem
Thank you to NORDIC SEMICONDUCTOR for the OpenSource App like nRF UART v2 to make it easy to use their products!!