// Hello World - Echo Test von S.F. webseite, usb.c file vom 27.2. 19:05

#include <stdio.h>
#include "stm32f0xx.h" //[ALEX]
#include "usb.h"



// The current clock frequency
//uint32_t SystemCoreClock=8000000;

// Counts milliseconds
//volatile uint32_t systick_count=0;

// Interrupt handler [ALEX] -> in stm32f0xx_it.c
//void SysTick_Handler(void)
//{
//   systick_count++;
//}

// Delay some milliseconds
void delay_ms(int ms)
{
    //[ALEX] uint32_t start=systick_count;
    uint32_t start=HAL_GetTick();
    while (HAL_GetTick()-start<ms);

}

// Change system clock to 48Mhz using 24Mhz crystal
// Called by Assembler startup code
void SystemInit(void)
{
	// Enable the Internal High Speed oscillator (HSI48)
   		SET_BIT(RCC->CR2, RCC_CR2_HSI48ON);
   		while (!READ_BIT(RCC->CR2, RCC_CR2_HSI48RDY));

 	// switch SYSCLK to HSI48
   		MODIFY_REG(RCC->CFGR, RCC_CFGR_SW, RCC_CFGR_SW_HSI48);
   		while (!READ_BIT(RCC->CFGR, RCC_CFGR_SWS_HSI48));

   	//  Configure the USB clock source
   		MODIFY_REG(RCC->CFGR3, RCC_CFGR3_USBSW, RCC_CFGR3_USBSW_HSI48);

 	SystemCoreClock = 48000000;

	// Initialize system timer
    SysTick_Config(SystemCoreClock/1000);

	//[ALEX]
    SET_BIT(RCC->APB2ENR, RCC_APB2ENR_SYSCFGEN);
	while (!READ_BIT(RCC->APB2ENR, RCC_APB2ENR_SYSCFGEN));

	//[ALEX]
	SET_BIT(RCC->APB1ENR, RCC_APB1ENR_PWREN);
	while (!READ_BIT(RCC->APB1ENR, RCC_APB1ENR_PWREN));

	//[ALEX] remap pins for USB
	SYSCFG->CFGR1 |= (SYSCFG_CFGR1_PA11_PA12_RMP);

	// Setup Clock Recovery System CRS to sync with USB SOF
   		// enable CRS
   		SET_BIT(RCC->APB1ENR, RCC_APB1ENR_CRSEN);
   		while (!READ_BIT(RCC->APB1ENR, RCC_APB1ENR_CRSEN));

   		// reset CRS
   		RCC->APB1RSTR |= (RCC_APB1RSTR_CRSRST);
   		RCC->APB1RSTR &= ~(RCC_APB1RSTR_CRSRST);

   		CRS->CFGR = CRS_CFGR_SYNCDIV_0 | 			// prescaler: no divider
    			CRS_CFGR_SYNCSRC_1 |  		// source: USB SOF
 				CRS_CFGR_SYNCPOL   |  		// polarity: falling
 				(47999U << CRS_CFGR_RELOAD_Pos) | // reload value
 				(34 << CRS_CFGR_FELIM_Pos); 	// error limit value
    			// reload value =  f_{target} / f_{sync} - 1
    			// reload value =  48e6/1e3 - 1 = 47999
    			// error limit value: from cubeMx code generator

   		// Adjust HSI48 oscillator smooth trimming
   		MODIFY_REG(CRS->CR, CRS_CR_TRIM, (32 << CRS_CR_TRIM_Pos));
    			// trim value: from cubeMx code genererator

   		// START AUTOMATIC SYNCHRONIZATION
   		SET_BIT(CRS->CR, CRS_CR_AUTOTRIMEN | CRS_CR_CEN);    	  // enable automatic trimming & frequency error counter


}

void init_io()
{
    // Enable USB
    SET_BIT(RCC->APB1ENR, RCC_APB1ENR_USBEN);

    // Enable Port A and C
    //[ALEX] SET_BIT(RCC->APB2ENR, RCC_APB2ENR_IOPAEN + RCC_APB2ENR_IOPCEN);

    // PA5 = Output (LED on Nucleo-64 board)
    //[ALEX] MODIFY_REG(GPIOA->CRL, GPIO_CRL_CNF5 + GPIO_CRL_MODE5, GPIO_CRL_MODE5_0);

    // PC13 = Output (LED on Blue-Pill board)
    //[ALEX] MODIFY_REG(GPIOC->CRH, GPIO_CRH_CNF13 + GPIO_CRH_MODE13, GPIO_CRH_MODE13_0);
}

// Alternative: Redirect standard output to the USB port, e.g. from puts() or printf()
int _write(int file, char *ptr, int len)
{
    for (int i=0; i<len; i++)
    {
        UsbCharOut(*ptr++);
    }
    return len;
}

int main(void)
{
	//[ALEX] remap pins for USB
	SYSCFG->CFGR1 |= (SYSCFG_CFGR1_PA11_PA12_RMP);

    init_io();
    UsbSetup();

    SET_BIT(USB->BCDR, USB_BCDR_DPPU);				// enable pullup USB

    while (1)
    {
        // LED On
    	//[ALEX]WRITE_REG(GPIOA->BSRR, GPIO_BSRR_BS5);
    	//[ALEX]WRITE_REG(GPIOC->BSRR, GPIO_BSRR_BR13);
        delay_ms(100);

        UsbStrOut("Hello World!\n");
        // Alternative: puts("Hello World!");

        // Send echo of received characters back
        while (UsbRxAvail())
        {
            char c=UsbGetChar();
            UsbCharOut(c);
        }

        // LED Off
        //[ALEX]WRITE_REG(GPIOA->BSRR, GPIO_BSRR_BR5);
        //[ALEX]WRITE_REG(GPIOC->BSRR, GPIO_BSRR_BS13);
        delay_ms(900);

    }

}