/* p3_3.c: Initialize and display "HELLO" on the LCD using 4-bit data mode.
 *
 * Because of 4-bit data mode, every byte of command or data is
 * transmitted twice, one for the upper nibble and one for lower nibble.
 * This program does not poll the status of the LCD.
 * It uses delay to wait out while LCD controller is busy.
 * For simplicity, all delay below 1 ms uses 1 ms. You may
 * want to adjust the amount of delay for your LCD controller
 * to enhance the performance.
 *
 * The LCD controller arduino shield is connected to the Nucleo-F030R8
 * board as follows:
 *
 * LCD  --> Arduino pin --> STM32F030R8 pin
 * DB4  --> Digital 4   --> PB5
 * DB5  --> Digital 5   --> PB4
 * DB6  --> Digital 6   --> PB10
 * DB7  --> Digital 7   --> PA8
 * RS   --> Digital 8   --> PA9
 * EN   --> Digital 9   --> PC7
 * BL   --> Digital 10  --> PB6
 *
 * This program was tested with Keil uVision v5.23 with DFP v2.0.0
 */

#include "stm32f0xx.h"

#define DB4 (1<<5)         /* PB5 mask for reg select */
#define DB5 (1<<4)         /* PB4 mask for enable */
#define DB6 (1<<10)        /* PB10 mask for reg select */
#define DB7 (1<<8)         /* PA8 mask for enable */
#define RS  (1<<9)         /* PA9 mask for reg select */
#define EN  (1<<7)         /* PC7 mask for enable */
#define BL  (1<<6)         /* PB6 mask for reg select */

#define SET_RS() GPIOA->BSRR = RS
#define CLR_RS() GPIOA->BSRR = RS<<16

#define SET_EN() GPIOC->BSRR = EN
#define CLR_EN() GPIOC->BSRR = EN<<16

void delayMs(int n);
void LCD_nibble_write(char data, unsigned char control);
void LCD_command(unsigned char command);
void LCD_data(char data);
void LCD_init(void);
void PORTS_init(void);


int main(void)
{
	/* initialize LCD controller */
	LCD_init();

	while (1) {
		/* Write "HELLO" on LCD */
		LCD_data('H');
		LCD_data('E');
		LCD_data('L');
		LCD_data('L');
		LCD_data('O');
		delayMs(1000);

		/* clear LCD display */
		LCD_command(1);
		delayMs(1000);
	}
}

/* initialize GPIOB/C then initialize LCD controller */
void LCD_init(void)
{
	PORTS_init();

	delayMs(20);            /* LCD controller reset sequence */
	LCD_nibble_write(0x30, 0);
	delayMs(5);
	LCD_nibble_write(0x30, 0);
	delayMs(1);
	LCD_nibble_write(0x30, 0);
	delayMs(1);

	LCD_nibble_write(0x20, 0);      /* use 4-bit data mode */
	delayMs(1);
	LCD_command(0x28);              /* set 4-bit data, 2-line, 5x7 font */
	LCD_command(0x06);              /* move cursor right */
	LCD_command(0x01);              /* clear screen, move cursor to home */
	LCD_command(0x0F);              /* turn on display, cursor blinking */
}

void PORTS_init(void)
{
	/* enable GPIOA/B/C clock */
	RCC->AHBENR |=  0x00020000;
	RCC->AHBENR |=  0x00040000;
	RCC->AHBENR |=  0x00080000;
	
/*
 * DB7  --> Digital 7   --> PA8
 * RS   --> Digital 8   --> PA9
 */
	GPIOA->MODER &= ~0x000F0000;    /* clear pin mode */
	GPIOA->MODER |=  0x00050000;    /* set pin output mode */
	
/*
 * DB4  --> Digital 4   --> PB5
 * DB5  --> Digital 5   --> PB4
 * DB6  --> Digital 6   --> PB10
 * BL   --> Digital 10  --> PB6
 */
	GPIOB->MODER &= ~0x00303F00;    /* clear pin mode */
	GPIOB->MODER |=  0x00101500;    /* set pin output mode */
	GPIOB->BSRR = BL;       				/* turn on Backlight */
	
/*
 * EN   --> Digital 9   --> PC7
 */
	GPIOC->MODER &= ~0x0000C000;    /* clear pin mode */
	GPIOC->MODER |=  0x00004000;    /* set pin output mode */
	GPIOC->BSRR = EN << 16;       /* turn off EN */
}

void LCD_nibble_write(char data, unsigned char control)
{
	uint16_t datamask = 0;
	/* populate data bits */
/*
 * LCD  --> Arduino pin --> STM32F030R8 pin
 * DB4  --> Digital 4   --> PB5
 * DB5  --> Digital 5   --> PB4
 * DB6  --> Digital 6   --> PB10
 * DB7  --> Digital 7   --> PA8
 */
	if(data & (1<<4)){
		datamask |= DB4;
	}
	if(data & (1<<5)){
		datamask |= DB5;
	}
	if(data & (1<<6)){
		datamask |= DB6;
	}
	
	
//	GPIOB->BSRR = (DB4|DB5|DB7)<<16 | datamask;
	GPIOB->BSRR = (DB4|DB5|DB6)<<16;
	GPIOB->BSRR = datamask;
	GPIOA->BSRR = DB7<<16 | ((data&(1<<7))?DB7:0);

	/* set R/S bit */
	if (control)
		SET_RS();
	else
		CLR_RS();

	/* pulse E */
	SET_EN();
	delayMs(0);
	CLR_EN();
}
void LCD_command(unsigned char command)
{
	LCD_nibble_write(command & 0xF0, 0);    /* upper nibble first */
	LCD_nibble_write(command << 4, 0);      /* then lower nibble */

	if (command < 4)
		delayMs(2);     /* command 1 and 2 needs up to 1.64ms */
	else
		delayMs(1);     /* all others 40 us */
}
void LCD_data(char data)
{
	LCD_nibble_write(data & 0xF0, 1);      /* upper nibble first */
	LCD_nibble_write(data << 4, 1);        /* then lower nibble */

	delayMs(1);
}
/* delay n milliseconds (8 MHz CPU clock) */
void delayMs(int n)
{
	int i;

	for (; n > 0; n--)
		for (i = 0; i < 1142; i++);
}