Low power i2c slave counter in pic12f629

Introduction

This project is a very simple counter with i2c interface designed for low power consumation. Most time counter sleeps and counting ticks in async timer mode.

Disclaimer

This is just my try hand at Microchip PIC assembler. The pic12 in crystal less mode probably worst choice for this project.We have only 10 instructions per I2C tick on even slow 100kHz bus speed. It was real challenge to make this thing work. After all it works quet good on 50kHz.

Sure this project not intended to run in production environment. But I used it in my weather station and it runs well capable low consumption and good stability

Compile

I used gptools to compile this project in mpasm compability mode. So most probable mpasm will work as well.

Hardware

CNT - 16bit Timer 1 counter pin

SDA - External interrupt pin (wakeups microcontroller for communication)

SCL - Any GPIO pin

       PIC12F629/75 
        -------          
      -|VCC GND|-         
  CNT -|GP5 GP0|-        
      -|GP4 GP1|- SCL    
      -|GP3 GP2|- SDA     
        -------    

License

MIT. See LICENSE file