STM32F103C8T6 Blue Pill And Character LCD Interfacing In 4-Bit Mode Example

In previous post, I showed about the LCD interfacing in 4-bit mode. The HD44780 allow the micro-processor to send the 8-bit data or command using an 4-bit interfacing. This process requires the microprocessor to send the 8-bit command or data twice over the 4-bit wire. The microprocessor send the higher nibble D4...D7 first, and then the lower nibble D0...D3. This technique saves the number of microprocessor digital output pins and circuit wiring. For more information about 4-bit LCD interfacing you can read this article.

Circuit Wiring On Bread Board

In this programming example, I use the lower byte of Port A. It's 16-bit wide. Where the LCD connections between the STM32F103C8R6 Blue Pill are,

• LCD Register Select (RS) connects to PA0,
• LCD Read or Write (R/W) connects to GND as the LCD just need to receive command or data,
• LCD Enable (EN) connects to PA1,
• LCD Data D0...D3 left unconnected or connects GND, while the LCD Data D4...D7 connects to the Blue Pill PA4...PA7.

STM32CubeIDE Code Configuration Wizard allows the programmer to select any peripherals and system settings without writing code in C/C++ source file.

GPIO Selection

In SYS tab I selected Serial Wire as its Debug interface. The System Wake-Up must left uncheck allowing PA0 as digital I/O.

I use its 8MHz HSI RC as the clock source (internal). There is no pre-scaling or post scaling of this clock source.

Clock Configuration

The schematic below uses a modified model of the Blue Pill in Proteus original library. It also able to simulate.

Schematic

The LCD module is low cost JHD16 that cost around 1USD.
 

JHD16 LCD Module Front

JHD16 LCD Module Back

The source source code is quite easy as it's similar to LCD interfacing in 8-bit mode.

/* 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"
 
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
 
/**
  * @brief  The application entry point.
  * @retval int
  */
 
#define DPORT GPIOA->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(100);
	temp=0;
	DPORT=temp|(cmd&0xF0);
	delay1(1000);
 
	temp=0x02;
	DPORT=temp|(cmd<<4);
	delay1(100);
	temp=0;
	DPORT=temp|(cmd<<4);
}
 
void lcdDat(uint8_t dat){
	uint8_t temp=0x03;
	DPORT=temp|(dat&0xF0);
	delay1(100);
	temp=0x01;
	DPORT=temp|(dat&0xF0);
	delay1(1000);
 
	temp=0x03;
	DPORT=temp|(dat<<4);
	delay1(100);
	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){
	// 16x2 LCD
	uint8_t tbe[2]={0x80,0xC0};
	// 20x4 LCD
	//uint8_t tbe[]={0x80,0xC0,0x94,0xD4};
	lcdCmd(tbe[y-1]+x-1);
	delay1(100);
}
 
void lcdClear(void){
	lcdCmd(0x01);
	delay1(100);
}
 
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(100);
 
  lcdXY(2,1);
  lcdStr("STM32F103C8T6");
  delay2(100);
  lcdXY(1,2);
  lcdStr("4-Bit Mode LCD");
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */
 
    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}
 
/**
  * @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_GPIOA_CLK_ENABLE();
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_4|GPIO_PIN_5
                          |GPIO_PIN_6|GPIO_PIN_7, GPIO_PIN_RESET);
 
  /*Configure GPIO pins : PA0 PA1 PA4 PA5
                           PA6 PA7 */
  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(GPIOA, &GPIO_InitStruct);
 
}
 
/**
  * @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 C/C++ loop to create delay without using the STM32CubeIDE Hal_Delay function. However the delay time is not known.

Simulating Program In Proteus

 Click here to download its source file.

STM32F103C8T6 Blue Pill And Character LCD Interfacing In 8-Bit Mode Example

In this ARM programming example, I will use an earlier day character LCD to show text. This character LCD conventionally uses an HD44780 LCD controller manufactured by Hitachi. Currently there are a lot of low cost equivalent LCD controllers.

Blue Pill Experiment On Bread Board

I will not write the details about this controller here because it's already explained in previous tutorial. But it uses the ATMega32 AVR micro-controller. 

Blue Pill Simulating Program Using Proteus VSM 8.15

I use the lower nibble of Port A to send command or data to LCD module. PortA is a 16-bit bi-directional I/O. PC14 connects to LCD Register Select (RS) while PC15 connects to LCD En (Enable). As we just needs to send data or command to LCD module, the LCD Read/Write (R/W) just connect to GND.

GPIO Setting In Device Configuration Tool

Without writing a legacy style C/C++ for ARM micro-controller, I use the Code Configuration Tool inside the STM32CubeIDE. It will generate C/C++ source code whenever we have finish all preferred setting on target MCU. 

SYS Setting

In SYS tab, I select Serial Wire as the debug interface with ST-LINK V2. The System Wake-Up check box must left unchecked to enable the PA0 as general purpose I/O.

/* 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"
 
void delay(uint16_t num){
	for(uint16_t i=0;i<num;i++);
}
 
void lcdCommand(uint16_t cmd){
	GPIOA->ODR=cmd;
	//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){
	GPIOA->ODR=data;
	//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++;
	}
}
 
void lcdClear(void){
	lcdCommand(0x01);
	delay(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();
  lcdGotoXy(3,1);
  lcdPrint("STM32F103C8T6");
  lcdGotoXy(1,2);
  lcdPrint("Blue Pill Module");
  for(uint8_t i=0;i<200;i++) delay(50000);
  lcdClear();
  lcdGotoXy(1,1);
  lcdPrint("LCD Programming");
  lcdGotoXy(3,2);
  lcdPrint("STM32CubeIDE");
 
  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
 
  }
  /* USER CODE END 3 */
}
 
/**
  * @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();
  __HAL_RCC_GPIOA_CLK_ENABLE();
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOC, RS_Pin|EN_Pin, GPIO_PIN_RESET);
 
  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3
                          |GPIO_PIN_4|GPIO_PIN_5|GPIO_PIN_6|GPIO_PIN_7, GPIO_PIN_RESET);
 
  /*Configure GPIO pins : RS_Pin EN_Pin */
  GPIO_InitStruct.Pin = RS_Pin|EN_Pin;
  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);
 
  /*Configure GPIO pins : PA0 PA1 PA2 PA3
                           PA4 PA5 PA6 PA7 */
  GPIO_InitStruct.Pin = GPIO_PIN_0|GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3
                          |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(GPIOA, &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 its internal HSI RC clock source. However this module has an external 8MHz crystal oscillator. Click here to download its source file.

Clock Configuration

I re-arrange the Blue Pill model in Proteus VSM 8.15. I want to make its pin map similar to the physical hardware.

Schematic Diagram

 

Top View #1

Top View #2

However it can simulate like the original model. The STM32 Blue Pill supply voltage is +3.3V while the LCD module supply voltage is +5V. The USB power bus gives the module a stable +5V DC voltage. I use another micro USB cable connects to the USB header on the STM32 Blue Pill module.

Using A +3.3V Supply Voltage For The LCD Module

However we can connect these modules to +5.0V supply voltage from the ST-LINK V2 debugger. As shown in the picture above, using a +3.3V supply for LCD module causing an insufficient power that make the display data unclear.