ARM Stopwatch Using LPC2148 Microcontroller

This project demonstrates a Digital Stopwatch using an ARM7-based LPC2148 Microcontroller. The stopwatch features Start, Stop, and Reset functionalities, and displays elapsed time on a 16x2 LCD.

Project Description

• Microcontroller: LPC2148 (ARM7TDMI-S Core)
• Features:
  • Start, Stop, and Reset controls using Push Buttons
  • Real-time time display on a 16x2 LCD
  • Timer0 interrupt-driven stopwatch functionality
  • Precision up to milliseconds
• Application: Digital Timers, Embedded Time-based Applications, Academic Projects.

Hardware Requirements

• LPC2148 Development Board
• 16x2 LCD: HD44780 compatible
• Push Buttons (3 units): For Start, Stop, Reset operations
• Power Supply: 3.3V regulated (with USB-UART or external power)
• Breadboard, Jumper Wires, Resistors

Software Requirements

• Keil uVision (for ARM C code compilation & HEX generation)
• Proteus Design Suite (for circuit simulation)
• Flash Magic (if flashing to hardware)

Project Folder Structure

arm-stopwatch/
├── src/
│   └── main.c               # C Source Code
├── simulation/
│   └── project.pdsprj       # Proteus simulation file
└── README.md                # Project Overview & Instructions

Steps to Compile HEX File in Keil

1. Open Keil uVision IDE.
2. Create a New Project:
   • Project > New Project
   • Name it: ARM_Stopwatch
3. Select Microcontroller:
   • From the device database, select NXP > LPC2148.
4. Add Source File to Project:
   • Right-click Source Group 1 > Add Existing Files to Group.
   • Browse and select main.c from /src/.
5. Configure Output HEX File:
   • Go to Project > Options for Target 'Target 1'.
   • Under Output tab, check "Create HEX File".
6. Build the Project:
   • Press F7 or go to Project > Build Target.
   • The generated HEX file will be located inside the project directory.

Running the Simulation in Proteus

Simulation Prerequisites:

• Ensure you have Proteus component libraries:
  • LPC2148 Microcontroller
  • HD44780 LCD (16x2)
  • Push Buttons
  • Resistors and Power Supply

Simulation Steps:

1. Open Proteus Design Suite.
2. Open the Provided Simulation File:
   • Navigate to /simulation/ folder.
   • Open project.pdsprj.
3. Load the HEX File to LPC2148:
   • Double-click on the LPC2148 symbol.
   • In the Program File field, browse and select the generated HEX file.
4. Run the Simulation:
   • Click Play (Run Simulation).

Operation Flow:

• Start Button (P0.14): Starts the stopwatch.
• Stop Button (P0.15): Pauses/Stops the stopwatch.
• Reset Button (P0.16): Stops and resets the stopwatch time to 00:00:000.
• The elapsed time is displayed on the LCD in mm:ss:ms format.

How the Code Works

• PLL is configured to run the system clock at 60MHz.
• LCD is interfaced in 4-bit mode for display operations.
• Timer0 is configured to trigger an interrupt every 1ms.
• Timer0 ISR increments the time counters (ms, sec, min) and updates the LCD display.
• Push Buttons are polled in a loop to control Start, Stop, and Reset functionalities.

Flowchart

Start
  |
  |---> Initialize PLL (60MHz)
  |---> Initialize LCD
  |---> Configure Timer0 for 1ms interrupts
  |---> Enable VIC interrupt for Timer0
  |
Main Loop:
  |
  |---> Check Start Button (P0.14)
  |        |
  |        +--> Set Run Flag = 1
  |
  |---> Check Stop Button (P0.15)
  |        |
  |        +--> Clear Run Flag = 0
  |
  |---> Check Reset Button (P0.16)
  |        |
  |        +--> Reset ms, sec, min = 0
  |        +--> Clear Run Flag = 0

Timer0 ISR (Every 1ms):
  |
  |---> If Run Flag == 1:
  |         |
  |         +--> Increment ms
  |         +--> Update sec and min when ms >= 1000 or sec >= 60
  |         +--> Refresh LCD Display with new Time
  |
  |---> Clear Timer0 Interrupt Flag
  |---> Return to Main Loop

Notes

• The LCD operates in 4-bit mode to save GPIO pins.
• The ISR is lightweight to ensure consistent timing.
• Buttons are polled instead of using interrupts for simplicity.
• Ensure debounce handling in hardware or via software if necessary.

Troubleshooting

• HEX File Not Loading in Proteus?
  • Ensure correct HEX file generation and path in Proteus.
  • Verify LPC2148 part is correctly placed in Proteus.
• LCD Not Displaying Correctly?
  • Check LCD pin connections and contrast settings.
• Button Response Delays?
  • Ensure proper grounding and debounce mechanisms.

License

This project is licensed under the MIT License. You are free to use, modify, and distribute this code and simulation files.

Preview (Add Screenshots in /docs/)

• Simulation Circuit Diagram
• LCD showing Stopwatch Ready
• LCD displaying running time

Author

GOKUL KRISHNA K S