🖥️ STM32F446RE – 16x2 LCD Display (Bare Metal Programming)

📘 Project Overview

This project demonstrates how to interface a 16x2 LCD display with the STM32F446RE microcontroller using bare-metal programming in Keil µVision.
All operations are performed using register-level access to the STM32 peripherals — no HAL, no CubeMX, just pure C and CMSIS.

The LCD is driven in 8-bit mode, and data/command operations are handled via GPIO control.

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⚙️ Hardware Setup

Microcontroller: STM32F446RE
IDE: Keil µVision
Programming Type: Bare Metal (Register-level)
LCD Type: 16x2 Character LCD (HD44780 compatible)
Connection Mode: 8-bit Parallel

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🧩 Pin Configuration

LCD Pin	Signal	STM32 Pin	Port	Pin No.	Direction
D0	Data 0	PA10	GPIOA	10	Output
D1	Data 1	PB3	GPIOB	3	Output
D2	Data 2	PB5	GPIOB	5	Output
D3	Data 3	PB4	GPIOB	4	Output
D4	Data 4	PB10	GPIOB	10	Output
D5	Data 5	PA8	GPIOA	8	Output
D6	Data 6	PA9	GPIOA	9	Output
D7	Data 7	PC7	GPIOC	7	Output
RS	Register Select	PA7	GPIOA	7	Output
RW	Read/Write	PB6	GPIOB	6	Output
EN	Enable	PA6	GPIOA	6	Output

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🧠 Code Explanation

1️⃣ GPIO Clock Enable

RCC->AHB1ENR |= (1<<0) | (1<<1) | (1<<2); // Enable clock for GPIOA, GPIOB, GPIOC

2️⃣ GPIO Mode Configuration

All LCD control and data pins are configured as output.

GPIOA->MODER |= (1<<12) | (1<<14) | (1<<16) | (1<<18) | (1<<20);
GPIOB->MODER |= (1<<6) | (1<<8) | (1<<10) | (1<<12) | (1<<20);
GPIOC->MODER |= (1<<14);

3️⃣ LCD Command & Data Flow

Command Function

Sends control instructions to the LCD.

void Lcd_Command(unsigned char command)
{
	Printdata(command);
	GPIOA->ODR &= ~(1<<7);  // RS = 0 for command
	GPIOB->ODR &= ~(1<<6);  // RW = 0 for write
	GPIOA->ODR |= (1<<6);   // EN = 1 (Enable pulse)
	delay(80000);
	GPIOA->ODR &= ~(1<<6);  // EN = 0
}

Data Function

Sends ASCII characters or data bytes to the LCD.

void Lcd_data(unsigned char data)
{
	Printdata(data);
	GPIOA->ODR |= (1<<7);   // RS = 1 for data
	GPIOB->ODR &= ~(1<<6);  // RW = 0 for write
	GPIOA->ODR |= (1<<6);   // EN = 1 (Enable pulse)
	delay(80000);
	GPIOA->ODR &= ~(1<<6);  // EN = 0
}

LCD Initialization

void Lcd_Initialise(void)
{
	Lcd_Command(0x38); // 8-bit, 2-line, 5x7 matrix
	Lcd_Command(0x06); // Increment cursor
	Lcd_Command(0x0C); // Display ON, cursor OFF
	Lcd_Command(0x01); // Clear display
}

💬 Display Output

Command Action 0x80 Set cursor to first line 0xC0 Set cursor to second line "Embedded" Displayed on first line "Systems" Displayed on second line

🖼️ Output

LCD Display:

Embedded Systems

🧩 Functions Summary

Function Description Printdata() Maps 8-bit data to GPIO pins Lcd_Command() Sends LCD command instructions Lcd_data() Sends display characters Lcd_String() Displays string on LCD Lcd_Initialise() Initializes LCD configuration

🕹️ Working Principle

GPIO ports are configured as outputs.

LCD initialized with command set.

Data bytes (characters) are sent one by one to form text.

Enable (EN) pulse latches each data/command to the LCD.

🧠 Key Learning Points

Register-level programming using RCC, GPIO MODER, and ODR.

Understanding LCD 8-bit communication without libraries.

Timing control via manual enable pulse and software delay.

Writing clean modular functions for LCD display control.

🚀 Future Enhancements

Implement 4-bit LCD mode to reduce pin usage.

Use SysTick timer for accurate delays.

Add custom character display using CGRAM commands.

Integrate with sensors and show data dynamically on LCD.