#include "stm32f4xx.h"
#include "stm32f4xx_rcc.c"
#include "stm32f4xx_gpio.c"
#include "stm32f4xx_usart.c"
#include "LCD2x16.c"
#include "dd.h"

char *OutString;        // string must be terminated by '\0'

GPIO_InitTypeDef        GPIO_InitStructure;
USART_InitTypeDef       USART_InitStructure;

//USART3 initialization, GPIOD 8:9, TX&RX, IRQ on RX&TX 
void USART3_init(int BaudRate)   {
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
  GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_8 | GPIO_Pin_9; 
  GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_NOPULL;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_Init(GPIOD, &GPIO_InitStructure); 
  GPIO_PinAFConfig(GPIOD, GPIO_PinSource8, GPIO_AF_USART3);
  GPIO_PinAFConfig(GPIOD, GPIO_PinSource9, GPIO_AF_USART3);
  
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3, ENABLE);
  USART_DeInit(USART3);
  USART_InitStructure.USART_BaudRate            = BaudRate;  
  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStructure.USART_Mode                = USART_Mode_Rx | USART_Mode_Tx;
  USART_InitStructure.USART_Parity              = USART_Parity_No;
  USART_InitStructure.USART_StopBits            = USART_StopBits_1;
  USART_InitStructure.USART_WordLength          = USART_WordLength_8b;
  USART_Init(USART3, &USART_InitStructure);
  
  USART_ITConfig(USART3, USART_IT_RXNE, ENABLE); // enable IRQ on RX
  
  USART_Cmd(USART3, ENABLE);
  NVIC_EnableIRQ(USART3_IRQn);   // Enable IRQ for USART3 in NVIC
}

// initialize port D (LEDS), Gpio_Pin_12 to GPIO_Pin_15 as outputs
void LEDinit (void)     {
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
  GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
  GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_OUT;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; 
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_NOPULL; 
  GPIO_Init(GPIOD, &GPIO_InitStructure); 
}

// initialize port E (switches), Gpio_Pin_3 to GPIO_Pin_6 as inputs
void SWITCHinit (void)  {
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);
  GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_3 | GPIO_Pin_4 | GPIO_Pin_5 | GPIO_Pin_6;
  GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_IN;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; 
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_DOWN;
  GPIO_Init(GPIOE, &GPIO_InitStructure); 
}

void main(void) {              

  LEDinit();
  SWITCHinit();
  USART3_init(921600);
  LCD_init();                  

  while (1) {
    if (GPIOE->IDR & S370) LED_GR_ON; else LED_GR_OFF;
    if (GPIOE->IDR & S373) USART3->DR = 'a';    // send    
    for (int i = 0; i<100000; i++) {};          // waste time
  };
}

// IRQ function
// caution: placing breakpoints in IRQ corrupts the execution!  
// this happends due to the reading of the DR by the IAR and changes IRQ flags!
// I wasted sevaral hours to figure this out; do not step into the same trap.
void USART3_IRQHandler(void)     {  
  // TX IRQ part
  if (USART3->SR & USART_SR_TXE) {    // If TXE flag in SR is on then
    if (*OutString != '\0')           // if not end of string
      USART3->DR = *OutString++;      // send next character & increment pointer
    else                              // else
      USART_ITConfig(USART3, USART_IT_TXE, DISABLE);
  };
  // RX IRQ part
  if (USART3->SR & USART_SR_RXNE) {   // if RXNE flag in SR is on then
    int RXch = USART3->DR;            // save received character & clear flag
    LCD_uInt16(RXch, 0x05, 1);        // show ASCII on LCD
    if (RXch == 'a') LED_BL_ON;   
    if (RXch == 'b') LED_BL_OFF;  
    if (RXch >= 'A' && RXch <= 'Z') USART3->DR = ++RXch;  // echo next character
    if (RXch == 'c') {                // if 'c' => return string
      OutString = "ABCDEFGH";         // Init string & ptr
      USART_ITConfig(USART3, USART_IT_TXE, ENABLE);
      USART3->DR = *OutString++;      // Send first character 
    };
  };
}