ESP8266 smart watch

Precautions:

• WiFi killer firmware cannot be used directly because the IIC pin definition is different and the source code needs to be modified and then flashed. The modified firmware is in the project attachment.
• The USB to serial port chip uses CP2102, and the corresponding driver needs to be installed.
• The program is compiled using ARDUINO IDE and some libraries need to be installed.
• Some of the APIs called in the program are free and you can apply for them yourself.
• When downloading using arduino IDE, the development board needs to check NodeMCU 1.0 (ESP-12E Module).

Areas for improvement:

• Energy consumption issue: ESP8266 has three sleep modes. To use deep sleep, you need to connect GPIO16 to the RESET pin; esp8266 uses the power supply to directly supply power, and the LDO can be controlled by the enable terminal to realize 3.3V switching.
• Add power supply voltage detection circuit.
• Power conversion: When the USB is connected, the system is powered by the USB power supply. When the USB is removed, the system is powered by the battery. Using the PMOS + Schottky diode solution, please refer to the following circuit:

• Peripherals can be added as needed, which will increase the difficulty of layout and routing.
• According to official recommendations, it is best for the antenna part of the ESP8266 module to extend outside the PCB, and the ground cannot be laid underneath. I did not notice this at the time, but I have not encountered any major problems so far.
• Using modules takes up too much space. ESP32-PCIO-D4 is a highly integrated esp32 chip. Using it to design the esp32 minimum system can greatly simplify the design of peripheral circuits. But WiFi Killer doesn't seem to support esp32.