#include "stm32f1xx.h"
#include <stdint.h>
#include <string.h>

// Konfigurasi I2C (PB6=SCL, PB7=SDA)
#define LCD_ADDR (0x27 << 1)  // Alamat I2C LCD (0x27 dalam 7-bit, digeser ke 8-bit)
#define I2C_TIMEOUT 100

// Fungsi delay sederhana
void delay_ms(uint32_t ms) {
  for (uint32_t i = 0; i < ms * 4000; i++) {
    __asm__("nop");
  }
}

// Inisialisasi I2C1
void I2C_Init() {
  // 1. Enable clock untuk GPIOB dan I2C1
  RCC->APB1ENR |= RCC_APB1ENR_I2C1EN;
  RCC->APB2ENR |= RCC_APB2ENR_IOPBEN;
  
  // 2. Konfigurasi PB6 (SCL) dan PB7 (SDA) sebagai alternate open-drain
  GPIOB->CRL &= ~(GPIO_CRL_CNF6 | GPIO_CRL_CNF7);
  GPIOB->CRL |= (GPIO_CRL_CNF6_1 | GPIO_CRL_CNF7_1);  // Alternate open-drain
  GPIOB->CRL |= (GPIO_CRL_MODE6 | GPIO_CRL_MODE7);    // Output mode 50MHz
  
  // 3. Konfigurasi I2C1
  I2C1->CR1 &= ~I2C_CR1_PE;  // Disable I2C sebelum konfigurasi
  I2C1->CR2 = (36 << 0);     // Freq clock (MHz) - misal 36MHz APB1
  I2C1->CCR = 180;           // Clock 100kHz (36MHz / (2*180) = 100kHz)
  I2C1->TRISE = 37;          // Rise time (1000ns / (1/36MHz) + 1)
  I2C1->CR1 |= I2C_CR1_PE;   // Enable I2C
}

// Kirim data via I2C
void I2C_Write(uint8_t addr, uint8_t data) {
  // 1. Tunggu sampai I2C tidak sibuk
  while (I2C1->SR2 & I2C_SR2_BUSY);
  
  // 2. Generate START condition
  I2C1->CR1 |= I2C_CR1_START;
  while (!(I2C1->SR1 & I2C_SR1_SB));
  
  // 3. Kirim alamat slave (mode write)
  I2C1->DR = addr;
  while (!(I2C1->SR1 & I2C_SR1_ADDR));
  (void)I2C1->SR2;  // Clear ADDR flag
  
  // 4. Kirim data
  while (!(I2C1->SR1 & I2C_SR1_TXE));
  I2C1->DR = data;
  while (!(I2C1->SR1 & I2C_SR1_BTF));
  
  // 5. Generate STOP condition
  I2C1->CR1 |= I2C_CR1_STOP;
}

// Kirim command ke LCD
void LCD_SendCmd(uint8_t cmd) {
  uint8_t upper = (cmd & 0xF0) | 0x04;  // EN=1, RS=0
  uint8_t lower = (cmd << 4) | 0x04;     // EN=1, RS=0
  
  I2C_Write(LCD_ADDR, upper);
  delay_ms(1);
  I2C_Write(LCD_ADDR, upper & ~0x04);    // EN=0
  delay_ms(1);
  
  I2C_Write(LCD_ADDR, lower);
  delay_ms(1);
  I2C_Write(LCD_ADDR, lower & ~0x04);    // EN=0
  delay_ms(1);
}

// Kirim data ke LCD
void LCD_SendData(uint8_t data) {
  uint8_t upper = (data & 0xF0) | 0x05;  // EN=1, RS=1
  uint8_t lower = (data << 4) | 0x05;    // EN=1, RS=1
  
  I2C_Write(LCD_ADDR, upper);
  delay_ms(1);
  I2C_Write(LCD_ADDR, upper & ~0x04);    // EN=0
  delay_ms(1);
  
  I2C_Write(LCD_ADDR, lower);
  delay_ms(1);
  I2C_Write(LCD_ADDR, lower & ~0x04);    // EN=0
  delay_ms(1);
}

// Inisialisasi LCD
void LCD_Init() {
  delay_ms(50);
  
  // Mode 4-bit
  LCD_SendCmd(0x33);
  LCD_SendCmd(0x32);
  LCD_SendCmd(0x28);  // 4-bit, 2 line, 5x8 font
  LCD_SendCmd(0x0C);  // Display on, cursor off
  LCD_SendCmd(0x06);  // Increment cursor
  LCD_SendCmd(0x01);  // Clear display
  delay_ms(2);
}

// Tulis string ke LCD
void LCD_Print(char *str) {
  while (*str) {
    LCD_SendData(*str++);
  }
}

int main(void) {
  // Inisialisasi
  I2C_Init();
  LCD_Init();
  
  // Tampilkan pesan
  LCD_SendCmd(0x80);  // Pindah ke baris 1, kolom 0
  LCD_Print("STM32 BluePill");
  
  LCD_SendCmd(0xC0);  // Pindah ke baris 2, kolom 0
  LCD_Print("LCD I2C Bare-Metal");
  
  while (1) {
    // Loop utama
  }
}