Embedded-Project

This is the Repositry for the embedded systems project

🕒 4-Digit 7-Segment Display Timer & Voltmeter (mbed - NUCLEO-F401RE)

📋 Overview

This project demonstrates how to use a 4-digit 7-segment display with a NUCLEO-F401RE development board and mbed OS. It has two operating modes:

1. Timer Mode (MM:SS) – counts up from 00:00 to 99:59
2. Voltage Mode – reads an analog voltage (via a potentiometer) and displays it as a 4-digit millivolt value (e.g., 3.30V → 3300)

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🔌 Hardware Connections

Component	NUCLEO Pin	Function
Latch (LCHCLK)	PB_5	DigitalOut
Clock (SFTCLK)	PA_8	DigitalOut
Data (SDI)	PA_9	DigitalOut
Reset Button (S1)	PA_1	DigitalIn
Mode Button (S3)	PB_0	DigitalIn
Potentiometer	PA_0	AnalogIn

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🧠 Core Concepts

🕓 1. Timer Mode (MM:SS Format)

• Time is tracked using a Ticker interrupt that fires every 1 second.
• The display updates across 4 digits:
  • Digits 0–1: Minutes (with a colon-like decimal on digit 1)
  • Digits 2–3: Seconds

🔋 2. Voltage Mode (0.00V - 3.30V)

• Voltage is read using an ADC input connected to a potentiometer.
• Converted from analog to millivolts and displayed over 4 digits.
  • E.g., 3.3V → 3300

🔁 3. Multiplexed Display Control

• Uses shift registers to drive the 7-segment display.
• A fast Ticker (1ms) triggers display refreshes, updating one digit at a time.
• The digits are cycled quickly to simulate a static image.

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🧱 Components Used

• NUCLEO-F401RE Board
• 4-digit 7-segment display with shift register
• Potentiometer (connected to analog pin)
• Two push buttons (for reset and mode switching)

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⌨️ Controls

Button	Action
S1	Reset time to 00:00 (only in timer mode)
S3	Hold to switch to voltage mode. Release to return to timer mode.

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🔧 How It Works (Code Breakdown)

Timekeeping

Ticker second_tick;
second_tick.attach(&tick, 1.0);

Increments total_seconds every second.

Display Refresh

Ticker refresh_tick;
refresh_tick.attach(&refreshISR, 0.001);

Triggers refresh every 1ms for multiplexing.

Segment Output

void outputToDisplay(uint8_t segments, uint8_t digitSelect)

Uses SPI-like bit-banging to send segment and digit control data to the shift registers.

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🧪 Notes

• Segment encoding is active-low (common anode display).
• Uses & 0x7F in digit 1 or voltage digit 0 to simulate a decimal point.
• Voltage is limited to 0–3.3V due to the MCU's ADC range.
• total_seconds wraps at 6000 seconds (99:59) to avoid overflow.