How to Implement an Embedded C Program for 7-Segment Display Using Interrupts

Creating an embedded C program that displays a two-digit number on a 7-segment display and increments the count when a switch is pressed can be a fun and educational project. This article will guide you through the process, including the necessary hardware setup, interrupt configuration, display logic, and main loop. We will assume you are using a microcontroller like the AVR series, such as the ATmega.

Overview

This guide will walk you through implementing an embedded C program that combines the functionality of a 7-segment display and an external interrupt triggered by a switch. The count should increment whenever the switch is pressed.

Hardware Setup

The hardware setup is crucial for this project. You will need to connect a 7-segment display and a switch to your microcontroller's pins. Here’s how to do it:

7-Segment Display: Connect each digit of the 7-segment display to the appropriate pins on the microcontroller (e.g., PORTB). Switch: Connect the switch to an input pin (e.g., PC0 on PORTC). Ensure you have a pull-up resistor in place to detect the switch state accurately.

Interrupt Configuration

Interrupts allow the microcontroller to handle external events, such as the switch being pressed, without constantly polling the pin. Here’s how to set up an external interrupt for the switch:

Configure the switch pin as an external interrupt using pin change interrupts. In the interrupt service routine (ISR), increment the count and debounce the switch input.

Here’s a sample code snippet for the interrupt setup:

```c#include #include #include #define SEGMENT_PORT PORTB // Port for 7-segment display#define SWITCH_PIN PC0 // Pin for the switch#define SWITCH_INT_PIN PCINT0 // External interrupt pinvolatile uint8_t count 0; // Variable to hold the count// 7-segment display encoding for digits 0-9const uint8_t segmentMap[10] { 0b00111111, // 0 0b00000110, // 1 0b01011011, // 2 0b01001111, // 3 0b01100110, // 4 0b01101101, // 5 0b01111101, // 6 0b00000111, // 7 0b01111111, // 8 0b01101111 // 9};void setup() { // Set PORTB as output for 7-segment display DDRB FF; // All pins on PORTB are outputs // Set up the switch pin as input DDRC ~SWITCH_PIN; // Set SWITCH_PIN as input PORTC | SWITCH_PIN; // Enable pull-up resistor // Enable external interrupt on pin PCICR | _BV(PCIE1); // Enable PCINT1 group PCMSK | _BV(SWITCH_INT_PIN); // Enable interrupt on the switch pin sei(); // Enable global interrupts}ISR(PCINT1_vect) { // Debouncing delay _delay_ms(50); if (!(PINC SWITCH_PIN)) { // Check if switch is still pressed count (count 1) % 100; // Increment count and wrap around at 100 }}```

Display Logic

The display logic converts the count to the corresponding 7-segment display representation. Here’s how to create a function for displaying a digit on the 7-segment display:

```cvoid displayDigit(uint8_t digit) { SEGMENT_PORT segmentMap[digit];}```

Main Loop

The main loop continuously updates the display based on the count variable. In this example, we will display the units place. Displaying the tens place would require additional logic.

```cint main() { setup(); while (1) { // Display the units digit displayDigit(count % 10); _delay_ms(500); // Delay for visibility } return 0;}```

Explanation

Hardware Connections: Connect the 7-segment display to PORTB of the microcontroller. Connect the switch to PORTC at PINC0 with a pull-up resistor. Interrupt Setup: Configure the switch pin as an external interrupt using pin change interrupts. The ISR increments the count and debounces the switch. Display Logic: The displayDigit function takes a digit 0-9 and outputs the corresponding binary value to the PORTB, driving the 7-segment display. Main Loop: The main loop continuously updates the display based on the count variable. You can modify this to display both the tens and units places.

Notes

Debouncing: The delay in the ISR is a simple debounce mechanism. For a more robust solution, consider implementing a more sophisticated debouncing algorithm. Multiplexed Display: This code assumes a simple 7-segment display. If you are using a multiplexed display, you will need to adjust the logic accordingly. Microcontroller Configuration: Make sure you have the appropriate configuration for your specific microcontroller, as pin numbers and port configurations may vary.

With these steps, you should have a good starting point to create your embedded C program for displaying a two-digit number on a 7-segment display using interrupts!