This PIC16F877 microcontroller tutorial answers the question,
” How to implement a stop watch using PIC16F877 ? ”
Using PIC16 simulator (Proteus) you can verify this stop watch code and change it according to your needs. Using three push buttons (As shown in figure below) you can adjust time as you desire. Then after setting the time, value displayed on the LCD starts to decrease with each second and when this value reaches zero, then LED D1 is turned on. This code is written in C language using MPLAB with HI-TECH C compiler. You can download this code from the ‘Downloads‘ section at the bottom of this page.
In this article, it is assumed that you know,
- How to make a simple digital clock using PIC16F877. If you don’t then please read this page.
- How to interface LCD with PIC16F877 microcontroller. If you don’t then please read this page.
- How to configure timer0 of PIC16F877 microcontroller. If you don’t then please read this page.
The following diagram (made in Proteus) shows the PIC microcontroller circuit diagram.
The above figure was taken when time was 00:00:07, i-e only 7 seconds were remaining until LED D1 is turned on. Timer0 is used as the base for digital clock generation. Timer0 is used here to generate 1msec interrupts. After every 1msec a global variable named msCounter increments. When msCounter reaches a value of 1000 then another global variable named secCounter decrements and this process repeats itself. Similarly, when secCounter reaches 0, then minCounter decrements. And when minCounter reaches 0 then hrCounter decrements. This process continues until hrCounter reaches 0. LCD is updated with the new values of hrCounter, minCounter and secCounter after every second.
You can set time using three push buttons attached on RE0, RE1 and RE2 pins (As shown in the above figure). By pressing ‘Set Time‘ button one time, code enters in configuration state. Hours value starts to blink and you can modify it using Up and Down buttons. Pressing Up button increments the value and pressing Down button decrements the value. When you are done setting Hours value, press ‘Set Time‘ button again, then Minutes value will start to blink and you can adjust this value using Up and Down buttons. Similarly, after setting Minutes value, you can press ‘Set Time‘ button again, then Seconds value will start to blink and you can adjust this value using Up and Down buttons. When you are done adjusting the time, then press ‘Set Time‘ button for the last time and this stop watch will start to work normally.
The main function code is shown below.
Stop watch clock display code using PIC16F877 was compiled in MPLAB v8.85 with HI-TECH C v9.83 compiler and simulation was made in Proteus v7.10. To download code and Proteus simulation click here.
For more detail: PIC16F877 stop watch code and Proteus simulation