STM32F103R6 GPIO Interfaces To A Character LCD In 8-Bit Mode

A character LCD has been an interesting staff for novice micro-controller learner. Prior to the present of C programming for micro-controller, the student used the Assembly language to program this character LCD. It requires a few dozens of Assembly codes.

Simulating Program In Proteus Using The STM32F103R6

Its original LCD controller was the Hitachi HD44780 chip. Currently it was replace by many other equivalent controller chip with low cost. For example, a 16x2 character LCD module costs around 1$. 

A typical character LCD module

A typical character LCD module

Its Pins Diagram

The interface between the micro-controller and this character LCD is a conventional parallel 8-bit data mode. However this LCD controller allow the program to use a 4-bit data transfer mode. You can see this tutorial for the LCD interface using 8-bit mode.

The LCD module is readable/writable. But we just write the command/data to this module is OK. The Register Select (RS) pin allow us to choose between command (RS=0) and data (RS=1). The Enable (E) pin allow the parallel data lath into the controller whenever there is a transition from High To Low. 

I use the STM32CubeIDE to write this code. It's very easy to use and it's free of charge. We need to register first before it allows us to download this IDE.

I select a number of output pin in code configuration wizard before it can generate the core source codes.

STM32F103R6 Pin Configuration In STM32CubeIDE

I need to write a few C functions to send the command and data to the LCD. And then I need to initialize the LCD module.

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; Copyright (c) 2022 STMicroelectronics.
  * All rights reserved.</center></h2>
  *
  * This software component is licensed by ST under BSD 3-Clause license,
  * the "License"; You may not use this file except in compliance with the
  * License. You may obtain a copy of the License at:
  *                        opensource.org/licenses/BSD-3-Clause
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
 
/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{
  /* USER CODE BEGIN 1 */
 
  /* USER CODE END 1 */
 
  /* MCU Configuration--------------------------------------------------------*/
 
  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();
 
  /* USER CODE BEGIN Init */
 
  /* USER CODE END Init */
 
  /* Configure the system clock */
  SystemClock_Config();
 
  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  lcdInit();
      lcdGotoXy(1,1);
      lcdPrint("STM32CubeIDE and");
      lcdGotoXy(1,2);
      lcdPrint("STM32F103R6 LCD");
  /* USER CODE BEGIN WHILE */
  while (1)
  {
 
  }
}
 
void delay(uint16_t num){
	for(uint16_t i=0;i<num;i++);
}
 
void lcdCommand(uint16_t cmd){
	GPIOB->ODR=cmd<<2;
	//GPIOB->ODR&=~(1<<RS_Pin);
	HAL_GPIO_WritePin(RS_GPIO_Port,RS_Pin,GPIO_PIN_RESET);
	//GPIOB->ODR|=(1<<EN_Pin);
	HAL_GPIO_WritePin(EN_GPIO_Port,EN_Pin,GPIO_PIN_SET);
	//HAL_Delay(1);
	delay(100);
	//GPIOB->ODR&=~(1<<EN_Pin);
	HAL_GPIO_WritePin(EN_GPIO_Port,EN_Pin,GPIO_PIN_RESET);
	//HAL_Delay(10);
	delay(10000);
}
 
void lcdData(uint8_t data){
	GPIOB->ODR=data<<2;
	//GPIOB->ODR|=(1<<RS_Pin);
	HAL_GPIO_WritePin(RS_GPIO_Port,RS_Pin,GPIO_PIN_SET);
	//GPIOB->ODR|=(1<<EN_Pin);
	HAL_GPIO_WritePin(EN_GPIO_Port,EN_Pin,GPIO_PIN_SET);
	//HAL_Delay(1);
	delay(10);
	//GPIOB->ODR&=~(1<<EN_Pin);
	HAL_GPIO_WritePin(EN_GPIO_Port,EN_Pin,GPIO_PIN_RESET);
	//HAL_Delay(10);
	delay(1000);
}
 
void lcdInit(void){
	//GPIOB->ODR&=~(1<<RS_Pin);
	HAL_GPIO_WritePin(EN_GPIO_Port,EN_Pin,GPIO_PIN_RESET);
	//HAL_Delay(2);
	delay(20000);
	lcdCommand(0x38);
	lcdCommand(0x0F);
	lcdCommand(0x01);
	//HAL_Delay(20);
	delay(20000);
	lcdCommand(0x06);
}
 
void lcdGotoXy(unsigned char x,unsigned char y){
	unsigned char charAddr[]={0x80,0xC0,0x94,0xD4};
	lcdCommand(charAddr[y-1]+x-1);
	//HAL_Delay(1);
	delay(1000);
}
 
void lcdPrint(char *str){
	unsigned char i=0;
	while(str[i]!=0){
		lcdData(str[i]);
		i++;
	}
}
 
/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
 
  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
 
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
  {
    Error_Handler();
  }
}
 
/**
  * @brief GPIO Initialization Function
  * @param None
  * @retval None
  */
static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
 
  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOB, RS_Pin|EN_Pin|GPIO_PIN_2|GPIO_PIN_3
                          |GPIO_PIN_4|GPIO_PIN_5|GPIO_PIN_6|GPIO_PIN_7
                          |GPIO_PIN_8|GPIO_PIN_9, GPIO_PIN_RESET);
 
  /*Configure GPIO pins : RS_Pin EN_Pin PB2 PB3
                           PB4 PB5 PB6 PB7
                           PB8 PB9 */
  GPIO_InitStruct.Pin = RS_Pin|EN_Pin|GPIO_PIN_2|GPIO_PIN_3
                          |GPIO_PIN_4|GPIO_PIN_5|GPIO_PIN_6|GPIO_PIN_7
                          |GPIO_PIN_8|GPIO_PIN_9;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
 
}
 
/* USER CODE BEGIN 4 */
 
/* USER CODE END 4 */
 
/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}
 
#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
 
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
 

Click here to download its source file.

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