Universal watch based on STM32

1. Principle
    This project uses STM32L431 as the main processing chip. This chip works at 80Mhz. It has a 12-bit precision ADC. The working voltage is 3.3V. It is a low-power chip in the STM32 family and has 5 low-power modes. ,
    the time part uses the DS1302 chip. This chip is widely used, cheap and easy to use. Project time can be shortened. 
    The analog data uses the AD8602 precision operational amplifier chip. The working voltage of this chip is compatible with STM32 and has excellent performance, which just meets the needs of this project.
    The power supply is powered by a lithium battery and has its own charging circuit. Currently, the lithium battery charging management solution is relatively mature, using the TP4056 chip, and the lithium battery core uses a soft-pack lithium battery to reduce the size.
    The display part uses a 0.9-inch segment LCD driven by Philips PCF8576C, which is very power-saving. It is cheap and sufficient for a watch display. It occupies relatively few system resources. The following is an introduction to this LCD screen: https://mastergong.cn/docs/display_specs/%5B50%5D0.9LCD.html
 
    
2. Functions
    This watch has two functions.
    First, it serves as a timekeeping watch. use. It can start from 2022 and time to 2099, with an annual error of less than 30 seconds. Currently it does not come with a lunar calendar, timer, or alarm clock. These functions will be added later with firmware updates. Normally displays time, date, year.
    Second, it can be used as a portable multimeter to measure common parameters such as voltage and resistance at any time. Due to various reasons such as power consumption, size, and the author's IQ, it cannot currently measure negative voltage, diode, and AC parameters.
   
3. Working parameters
need to be updated
4.
See attachment below