STM32F103R6 Interfaces To Character LCD In 4-Bit Mode

In previous post, I showed a simple programming example of using a character LCD with the STM32F103R6 ARM micro-controller using an 8-bit data bus. As it's already known, this LCD module is able to accept data from the micro-controller using 4-bit data bus. However the whole data ore command is still 8-bit wide. The MCU need to send data twice. The higher nibble needed to send and latch into the LCD module first. Then the lower nibble will be sent and latched into the LCD module.

Program Simulation

In this programming example, I will use PORTC of the STM32F103R6 to interface with the HD44780 LCD module. Where,

• PC0 connects to LCD Register Select (RS)
• LCD Read/Write (R/W) connects to GND as we only need to write data or command to the LCD module
• PC1 connects to LCD Enable (E) pin. It latches data into the LCD module whenever a High to Low transition occurs.
• PC4...PC7 connect to LCD data bus D4...D7.

Anyway the programmer should select other port or pin number of this micro-controller.

Device Configuration Tool

 

Device Configuration Tool could generates the source code for target controller without writing code.

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; Copyright (c) 2023 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"
 
#define DPORT GPIOC->ODR
 
void delay1(uint16_t dTime){
	for(uint16_t i=0;i<dTime;i++);
}
 
void delay2(uint8_t dTime){
	for(uint8_t i=0;i<dTime;i++) delay1(5000);
}
 
void lcdCmd(uint8_t cmd){
	uint8_t temp=0x02;
	DPORT=temp|(cmd&0xF0);
	delay1(10);
	temp=0;
	DPORT=temp|(cmd&0xF0);
	delay1(100);
 
	temp=0x02;
	DPORT=temp|(cmd<<4);
	delay1(10);
	temp=0;
	DPORT=temp|(cmd<<4);
}
 
void lcdDat(uint8_t dat){
	uint8_t temp=0x03;
	DPORT=temp|(dat&0xF0);
	delay1(10);
	temp=0x01;
	DPORT=temp|(dat&0xF0);
	delay1(100);
 
	temp=0x03;
	DPORT=temp|(dat<<4);
	delay1(10);
	temp=0x01;
	DPORT=temp|(dat<<4);
}
 
void lcdInit(void){
	DPORT=0x00;
	delay1(2000);
	lcdCmd(0x33);
	delay1(100);
	lcdCmd(0x32);
	delay1(100);
	lcdCmd(0x28);
	delay1(100);
	lcdCmd(0x0F);
	delay1(100);
	lcdCmd(0x01);
	delay1(2000);
	lcdCmd(0x06);
	delay1(100);
}
 
void lcdStr(uint8_t *str){
	while(*str) lcdDat(*str++);
}
 
void lcdXY(uint8_t x,uint8_t y){
	// 20x4 LCD
	uint8_t tbe[]={0x80,0xC0,0x94,0xD4};
	lcdCmd(tbe[y-1]+x-1);
	delay1(100);
}
 
void lcdClear(void){
	lcdCmd(0x01);
	delay1(100);
}
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
 
/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{
  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();
 
  /* Configure the system clock */
  SystemClock_Config();
 
  /* Initialize all configured peripherals */
  MX_GPIO_Init();
 
  lcdInit();
  lcdClear();
  delay2(200);
 
  lcdXY(5,1);
  lcdStr("Hello World!");
  delay2(100);
 
  lcdXY(1,2);
  lcdStr("STM32F103R6Tx ARM");
  delay2(100);
 
  lcdXY(1,3);
  lcdStr("Cortex-M3 Processor");
  delay2(200);
 
  lcdXY(5,4);
  lcdStr("STM32CubeIDE");
  delay2(200);
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
 
  }
}
 
/**
  * @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_GPIOC_CLK_ENABLE();
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_4|GPIO_PIN_5
                          |GPIO_PIN_6|GPIO_PIN_7, GPIO_PIN_RESET);
 
  /*Configure GPIO pins : PC0 PC1 PC4 PC5
                           PC6 PC7 */
  GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_4|GPIO_PIN_5
                          |GPIO_PIN_6|GPIO_PIN_7;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOC, &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****/
  

I use a 20x4 character LCD. If you prefer a 16x2 LCD you need to modify its display RAM address in the program. Click here to download its source file.