#include "main.h"
#include "stm32l100c_discovery.h"
#include "ssd1306.h"
#include "config.h"

// USB includes
#include "hw_config.h"
#include "usb_lib.h"
#include "usb_desc.h"
#include "usb_pwr.h"
#include "stringhelpers.h"

// TODO: Grab buttonpresses with interrupts
// TODO: Eliminate screen buffer since we aren't using it...

// USB Supporting Vars
extern __IO uint8_t Receive_Buffer[64];
extern __IO  uint32_t Receive_length ;
extern __IO  uint32_t length ;
uint8_t Send_Buffer[64];
uint32_t packet_sent=1;
uint32_t packet_receive=1;

// State definition
enum state {
    STATE_IDLE = 0,

    STATE_SETP,
    STATE_SETI,
    STATE_SETD,
    STATE_SETWINDUP,

    STATE_PREHEAT_BREW,
    STATE_MAINTAIN_BREW,
    STATE_PREHEAT_STEAM,
    STATE_MAINTAIN_STEAM,
};


static __IO uint32_t TimingDelay;

// Move to header file
void init_gpio();
void init_spi();
void process();
void machine();
void delay(__IO uint32_t nTime);

int main(void)
{

    // Init clocks
    SystemInit();

    // Init GPIO
    init_gpio();

    // Init USB
    //Set_USBClock();
    //USB_Interrupts_Config();
    //USB_Init();

    // Turn on power LED
    GPIO_SetBits(LED_POWER);

    // TODO: Awesome pwm of power LED (TIM4_CH4 or TIM11_CH1)
    // TODO: PWM of stat led (TIM3_CH2)

    // Configure 1ms SysTick (change if more temporal resolution needed) 
    RCC_ClocksTypeDef RCC_Clocks;
    RCC_GetClocksFreq(&RCC_Clocks);
    SysTick_Config(RCC_Clocks.HCLK_Frequency / 1000);

    // Init SPI busses
    init_spi();

    // Init OLED over SPI
    ssd1306_Init();
    ssd1306_clearscreen();

    // Startup screen 
    ssd1306_DrawString("therm v0.1", 1, 40);
    ssd1306_DrawString("protofusion.org/therm", 3, 0);
    delay(1500);
    ssd1306_clearscreen();

    GPIO_ResetBits(LED_STAT);

    // Main loop
    while(1)
    {
        // Process sensor inputs
        process();

        // Run state machine
        machine(); 
    }
}

// Read temperature and update global temp vars
int16_t temp = 0;
uint8_t temp_frac = 0;

void update_temp() {
    // Assert CS
    GPIO_ResetBits(MAX_CS);
    delay(1);

    // This may not clock at all... might need to send 16 bits first
    SPI_I2S_SendData(SPI2, 0xAAAA); // send dummy data
    //SPI_I2S_SendData(SPI2, 0xAA); // send dummy data
    uint16_t temp_pre = SPI_I2S_ReceiveData(SPI2);

    if(temp_pre & 0b0000000000000010) {
        ssd1306_DrawString("Fatal Error", 2, 35);
    }
    else if(temp_pre & 0b0000000000000001) {
        ssd1306_DrawString("Error: No TC", 2, 40);
        temp = 0;
        temp_frac = 0;
    }
    else 
    {
        uint8_t sign = temp >> 15;// top bit is sign

        temp_pre = temp_pre >> 2; // Drop 2 lowest bits
        temp_frac = temp_pre & 0b11; // get fractional part
        temp_frac *= 25; // each bit is .25 a degree, up to fixed point
        temp_pre = temp_pre >> 2; // Drop 2 fractional bits 

        if(sign) {
            temp = -temp_pre;
        }
        else {
            temp = temp_pre;
        }
    }

    // Deassert CS
    delay(1);
    GPIO_SetBits(MAX_CS);
}


// PID implementation
int16_t last_pid_temp = 0;
uint8_t last_pid_temp_frac = 0;
int16_t i_state = 0;

#define WINDUP_GUARD_GAIN 100
uint16_t windup_guard = WINDUP_GUARD_GAIN;

int16_t update_pid(uint16_t k_p, uint16_t k_i, uint16_t k_d, int16_t temp, uint8_t temp_frac, int16_t setpoint) 
{
  // Calculate instantaneous error
  int16_t error = (int16_t)setpoint - (int16_t)temp; // TODO: Use fixed point fraction

  // Proportional component
  int16_t p_term = k_p * error;

  // Error accumulator (integrator)
  i_state += error;

  // to prevent the iTerm getting huge despite lots of 
  //  error, we use a "windup guard" 
  // (this happens when the machine is first turned on and
  // it cant help be cold despite its best efforts)
  // not necessary, but this makes windup guard values 
  // relative to the current iGain
  int16_t windup_guard_res = WINDUP_GUARD_GAIN / k_i;  

  // Calculate integral term with windup guard 
  if (i_state > windup_guard_res) 
    i_state = windup_guard_res;
  else if (i_state < -windup_guard_res) 
    i_state = -windup_guard_res;
  int16_t i_term = k_i * i_state;

  // Calculate differential term (slope since last iteration)
  int16_t d_term = (k_d * (temp - last_pid_temp));

  // Save temperature for next iteration
  last_pid_temp = temp;
  last_pid_temp_frac = temp_frac;

  int16_t result = p_term + i_term - d_term;

  // Put out tenths of percent, 0-1000. 
  if(result > 1000)
    result = 1000;
  else if(result < -1000)
    result = -1000;

  // Return feedback
  return result;
}




uint32_t ticks = 0;
uint32_t last_ssr_on = 0;
uint32_t last_led = 0;
int32_t setpoint = 0;
uint16_t k_p = 1;
uint16_t k_i = 1;
uint16_t k_d = 1;
int16_t ssr_output = 0; // Duty cycle of ssr, 0 to SSR_PERIOD 
uint8_t pid_enabled = 0;

// Process things
void process()
{
    update_temp(); // Read MAX31855

    // TODO: Add calibration offset (linear)

    if(ticks - last_led > 400) 
    {
        GPIO_ToggleBits(LED_POWER);
        last_led = ticks;
    }

    // Every 200ms, set the SSR on unless output is 0
    if((ticks - last_ssr_on > SSR_PERIOD))
    {
        if(pid_enabled) 
        {
            // Get ssr output for next time
            int16_t power_percent = update_pid(k_p, k_i, k_d, temp, temp_frac, setpoint);
            //power-percent is 0-1000
            ssr_output = power_percent; //(((uint32_t)SSR_PERIOD * (uint32_t)10 * (uint32_t)100) * power_percent) / (uint32_t)1000000;
        }
        else 
        {
            ssr_output = 0;
        }

        // Only support heating (ssr_output > 0) right now
        if(ssr_output > 0) {

            char tempstr[6];
            itoa(ssr_output, tempstr);
            ssd1306_DrawString("#=", 2, 45);
            ssd1306_DrawString("    ", 2, 57);
            ssd1306_DrawString(tempstr, 2, 57);

            GPIO_SetBits(LED_STAT);
            last_ssr_on = ticks;
        }
    }
    
    // Kill SSR after elapsed period less than SSR_PERIOD 
    if(ticks - last_ssr_on > ssr_output)
    {
        GPIO_ResetBits(LED_STAT);
    }
}

void draw_setpoint() {
    char tempstr[3];
    itoa_fp(temp, temp_frac, tempstr);
    //ssd1306_DrawString("        ", 3, 40);
    ssd1306_DrawString(tempstr, 3, 40);
    ssd1306_DrawString("-> ", 3, 80);
    itoa(setpoint, tempstr);
    ssd1306_DrawString("    ", 3, 95);
    ssd1306_DrawString(tempstr, 3, 95);
}

uint8_t state = STATE_IDLE;
uint8_t goto_mode = 2;

// State machine
uint8_t sw_btn_last = 0;
uint8_t sw_up_last = 0;
uint8_t sw_down_last = 0;
uint8_t sw_left_last = 0;
uint8_t sw_right_last = 0;

#define SW_BTN_PRESSED (sw_btn_last == 0 && sw_btn == 1) // rising edge on buttonpress
#define SW_UP_PRESSED (sw_up_last == 0 && sw_up == 1)
#define SW_DOWN_PRESSED (sw_down_last == 0 && sw_down == 1)
#define SW_LEFT_PRESSED (sw_left_last == 0 && sw_left == 1)
#define SW_RIGHT_PRESSED (sw_right_last == 0 && sw_right == 1)

void machine()
{
    uint8_t last_state = state;

    uint8_t sw_btn = !GPIO_ReadInputDataBit(SW_BTN);
    uint8_t sw_up = !GPIO_ReadInputDataBit(SW_UP);
    uint8_t sw_down = !GPIO_ReadInputDataBit(SW_DOWN);
    uint8_t sw_left = !GPIO_ReadInputDataBit(SW_LEFT);
    uint8_t sw_right = !GPIO_ReadInputDataBit(SW_RIGHT);

    switch(state)
    {
        // Idle state
        case STATE_IDLE:
        {
            // Write text to OLED
            // [ therm :: idle ]
            ssd1306_DrawString("therm :: idle ", 0, 40);
            pid_enabled = 0;

            char tempstr[6];
            itoa_fp(temp, temp_frac, tempstr);
            ssd1306_DrawString("Temp: ", 3, 40);
            ssd1306_DrawString("    ", 3, 72);
            ssd1306_DrawString(tempstr, 3, 72);

            ssd1306_drawlogo();

            switch(goto_mode) {
                case 2:
                {
                    ssd1306_DrawString("-> brew     ", 1, 40);
                } break;

                case 1:
                {
                    ssd1306_DrawString("-> setup    ", 1, 40);
                } break;

                case 0:
                {
                    ssd1306_DrawString("-> reset    ", 1, 40);
                } break;
            }

            // Button handler
            if(SW_BTN_PRESSED) {
                switch(goto_mode) {
                    case 2:
                        state = STATE_PREHEAT_BREW;
                        break;
                    case 1:
                        state = STATE_SETP;
                        break;
                    case 0:
                        state = STATE_IDLE;
                        break;
                    default:
                        state = STATE_PREHEAT_BREW;
                }
            }
            else if(SW_UP_PRESSED && goto_mode < 2) {
                goto_mode++;
            }
            else if(SW_DOWN_PRESSED && k_p > 0 && goto_mode > 0) {
                goto_mode--;
            }


            // Event Handler
            // N/A

        } break;

        case STATE_SETP:
        {
            // Write text to OLED
            // [ therm :: set p ]
            // [ p = 12         ]
            ssd1306_DrawString("Proportional", 0, 40);
            ssd1306_drawlogo();

            char tempstr[6];
            itoa(k_p, tempstr);
            ssd1306_DrawString("P=", 1, 45);
            ssd1306_DrawString("    ", 1, 57);
            ssd1306_DrawString(tempstr, 1, 57);

            ssd1306_DrawString("Press to accept", 3, 40);
            
            // Button handler
            if(SW_BTN_PRESSED) {
                state = STATE_SETI;
            }
            else if(!GPIO_ReadInputDataBit(SW_UP)) {
                k_p++;
            }
            else if(!GPIO_ReadInputDataBit(SW_DOWN) && k_p > 0) {
                k_p--;
            }

            // Event Handler
            // N/A
 
        } break;

        case STATE_SETI:
        {
            // Write text to OLED
            // [ therm :: set i ]
            // [ i = 12         ]
            ssd1306_DrawString("Integral", 0, 40);
            ssd1306_drawlogo();

            char tempstr[6];
            itoa(k_i, tempstr);
            ssd1306_DrawString("I=", 1, 45);
            ssd1306_DrawString("    ", 1, 57);
            ssd1306_DrawString(tempstr, 1, 57);

            ssd1306_DrawString("Press to accept", 3, 40);
            
            // Button handler
            if(SW_BTN_PRESSED) {
                state = STATE_SETD;
            }
            else if(!GPIO_ReadInputDataBit(SW_UP)) {
                k_i++;
            }
            else if(!GPIO_ReadInputDataBit(SW_DOWN) && k_i > 0) {
                k_i--;
            }


            // Event Handler
            // N/A
 
        } break;

        case STATE_SETD:
        {
            // Write text to OLED
            // [ therm :: set d ]
            // [ d = 12         ]
            ssd1306_DrawString("Derivative", 0, 40);
            ssd1306_drawlogo();

            char tempstr[6];
            itoa(k_d, tempstr);
            ssd1306_DrawString("D=", 1, 45);
            ssd1306_DrawString("    ", 1, 57);
            ssd1306_DrawString(tempstr, 1, 57);

            ssd1306_DrawString("Press to accept", 3, 40);

            // Button handler
            if(SW_BTN_PRESSED) {
                state = STATE_SETWINDUP;
            }
            else if(!GPIO_ReadInputDataBit(SW_UP)) {
                k_d++;
            }
            else if(!GPIO_ReadInputDataBit(SW_DOWN) && k_d > 0) {
                k_d--;
            }

            // Event Handler
            // N/A
 
        } break;

        case STATE_SETWINDUP:
        {
            // Write text to OLED
            // [ therm :: set windup ]
            // [ g = 12         ]
            ssd1306_DrawString("Windup Guard", 0, 40);
            ssd1306_drawlogo();

            char tempstr[6];
            itoa(windup_guard, tempstr);
            ssd1306_DrawString("G=", 1, 45);
            ssd1306_DrawString("    ", 1, 57);
            ssd1306_DrawString(tempstr, 1, 57);

            ssd1306_DrawString("Press to accept", 3, 40);

            // Button handler
            if(SW_BTN_PRESSED) {
                state = STATE_IDLE;
            }
            else if(!GPIO_ReadInputDataBit(SW_UP)) {
                windup_guard++;
            }
            else if(!GPIO_ReadInputDataBit(SW_DOWN) && windup_guard > 0) {
                windup_guard--;
            }

            // Event Handler
            // N/A
 
        } break;




        case STATE_PREHEAT_BREW:
        {
            // Write text to OLED
            // [ therm : preheating brew ]
            // [ 30 => 120 C             ]
            ssd1306_DrawString("Preheating...", 0, 40);
            ssd1306_drawlogo();
            draw_setpoint();
            pid_enabled = 1;

            // Button handler
            if(SW_BTN_PRESSED) {
                state = STATE_IDLE;
            }
            else if(!GPIO_ReadInputDataBit(SW_UP)) {
               setpoint++; 
            }
            else if(!GPIO_ReadInputDataBit(SW_DOWN) && setpoint > 0) {
                setpoint--;
            }


            // Event Handler
            if(temp >= setpoint) {
                state = STATE_MAINTAIN_BREW;
            }
 
        } break;

        case STATE_MAINTAIN_BREW:
        {
            // Write text to OLED
            // [ therm : ready to brew ]
            // [ 30 => 120 C           ]
            ssd1306_DrawString("Ready to Brew!", 0, 40);
            ssd1306_drawlogo();
            draw_setpoint();
            pid_enabled = 1;

            // Button handler
            if(SW_BTN_PRESSED) {
                state = STATE_IDLE;
            }
            else if(!GPIO_ReadInputDataBit(SW_UP)) {
               setpoint++; 
            }
            else if(!GPIO_ReadInputDataBit(SW_DOWN) && setpoint > 0) {
                setpoint--;
            }


            // Event Handler
            // N/A
 
        } break;

        case STATE_PREHEAT_STEAM:
        {
            // Write text to OLED
            // [ therm : preheating steam ]
            // [ 30 => 120 C           ]
            ssd1306_DrawString("Preheating...", 0, 40);
            ssd1306_drawlogo();
            draw_setpoint();
            pid_enabled = 1;

            // Button handler
            if(SW_BTN_PRESSED) {
                state = STATE_IDLE;
            }
            else if(!GPIO_ReadInputDataBit(SW_UP)) {
               setpoint++; 
            }
            else if(!GPIO_ReadInputDataBit(SW_DOWN) && setpoint > 0) {
                setpoint--;
            }


            // Event Handler
            if(temp >= setpoint) {
                state = STATE_MAINTAIN_STEAM;
            }
 
        } break;

        case STATE_MAINTAIN_STEAM:
        {
            // Write text to OLED
            // [ therm : ready to steam ]
            // [ 30 => 120 C            ]
            ssd1306_DrawString("Ready to Steam!", 0, 40);
            ssd1306_drawlogo();
            draw_setpoint();
            pid_enabled = 1;

            // Button handler
            if(SW_BTN_PRESSED) {
                state = STATE_IDLE;
            }
            else if(!GPIO_ReadInputDataBit(SW_UP)) {
               setpoint++; 
            }
            else if(!GPIO_ReadInputDataBit(SW_DOWN) && setpoint > 0) {
                setpoint--;
            }


            // Event Handler
            // N/A
 
        } break;

        // Something is terribly wrong
        default:
        {
            state = STATE_IDLE;
            pid_enabled = 0;

        } break;
            
    }

    if(last_state != state) {
        // Clear screen on state change
        ssd1306_clearscreen();
    }
    sw_btn_last = sw_btn;
    sw_up_last = sw_up;
    sw_down_last = sw_down;
    sw_left_last = sw_left;
    sw_right_last = sw_right;
}


// Delay a number of systicks
void delay(__IO uint32_t nTime)
{
  TimingDelay = nTime;
  while(TimingDelay != 0);
}

// ISR-triggered decrement of delay and increment of tickcounter
void TimingDelay_Decrement(void)
{
  if (TimingDelay != 0x00)
  { 
    TimingDelay--;
  }
  ticks++;
}


void init_spi(void)
{
    SPI_InitTypeDef  SPI_InitStructure;

    // OLED IC
    SPI_Cmd(SPI1, DISABLE); 
    SPI_InitStructure.SPI_Direction = SPI_Direction_1Line_Tx;
    SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
    SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
    SPI_InitStructure.SPI_CPOL = SPI_CPOL_High;
    SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;
    SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
    SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4;
    SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
    SPI_InitStructure.SPI_CRCPolynomial = 7;
    SPI_Init(SPI1, &SPI_InitStructure);
    SPI_Cmd(SPI1, ENABLE);           /* Enable the SPI  */   


    // MAX IC
    SPI_Cmd(SPI2, DISABLE); 
    SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
    SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
    SPI_InitStructure.SPI_DataSize = SPI_DataSize_16b; // Andysworkshop
    SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low; // From andysworkshop
    SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge; // same
    SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
    SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8;
    SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
    SPI_InitStructure.SPI_CRCPolynomial = 7;
    SPI_Init(SPI2, &SPI_InitStructure);
    SPI_Cmd(SPI2, ENABLE);           /* Enable the SPI */
}

void init_gpio(void) {

 GPIO_InitTypeDef GPIO_InitStruct;

  // Enable SPI clocks
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);

  // Enable GPIO clocks
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC|RCC_AHBPeriph_GPIOB|RCC_AHBPeriph_GPIOA, ENABLE);

  // Enable DMA clocks (Is AHB even the right thing???)
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE); // EMZ TODO get the right ones

  /*Configure GPIO pin : PC */
  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_13;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;
  GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_400KHz;
  GPIO_Init(GPIOC, &GPIO_InitStruct);

  /*Configure GPIO pin : PB */
  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_1|GPIO_Pin_2|GPIO_Pin_10|GPIO_Pin_12 
                          |GPIO_Pin_9;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;
  GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_400KHz;
  GPIO_Init(GPIOB, &GPIO_InitStruct);

  /*Configure GPIO pin : PA */
  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_15;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;
  GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_400KHz;
  GPIO_Init(GPIOA, &GPIO_InitStruct);

  /*Configure GPIO pin : PB */
  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_3|GPIO_Pin_4|GPIO_Pin_5|GPIO_Pin_6 
                          |GPIO_Pin_7;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_Init(GPIOB, &GPIO_InitStruct);

  /** SPI1 GPIO Configuration  
  PA5   ------> SPI1_SCK
  PA7   ------> SPI1_MOSI
  */

  /*Enable or disable the AHB peripheral clock */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);

  /*Configure GPIO pin : PA: MOSI,SCK */
  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_5|GPIO_Pin_7;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_10MHz;
  GPIO_Init(GPIOA, &GPIO_InitStruct);

  /*Configure GPIO pin alternate function */
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_SPI1);

  /*Configure GPIO pin alternate function */
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource7, GPIO_AF_SPI1);

  /** SPI2 GPIO Configuration  
  PB13   ------> SPI2_SCK
  PB14   ------> SPI2_MISO
  PB15   ------> SPI2_MOSI
  */

  /*Enable or disable the AHB peripheral clock */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);

// SPI PINSSS

  /*Configure GPIO pin : PB, MOSI, SCK */
  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_13|GPIO_Pin_15;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_10MHz;
  GPIO_Init(GPIOB, &GPIO_InitStruct);

 GPIO_InitTypeDef GPIO_InitStruct2;
// MISO
  GPIO_InitStruct2.GPIO_Pin = GPIO_Pin_14;
  GPIO_InitStruct2.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStruct2.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStruct2.GPIO_Speed = GPIO_Speed_10MHz;
  GPIO_Init(GPIOB, &GPIO_InitStruct2);


  //Configure GPIO pin alternate function 
  GPIO_PinAFConfig(GPIOB, GPIO_PinSource13, GPIO_AF_SPI2);
  GPIO_PinAFConfig(GPIOB, GPIO_PinSource14, GPIO_AF_SPI2);
  GPIO_PinAFConfig(GPIOB, GPIO_PinSource15, GPIO_AF_SPI2);


  /** USB GPIO Configuration  
  PA11   ------> USB_DM
  PA12   ------> USB_DP
  */

  /*Enable or disable the AHB peripheral clock */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);

  /*Configure GPIO pin : PA */
  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_11|GPIO_Pin_12;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_400KHz;
  GPIO_Init(GPIOA, &GPIO_InitStruct);
}

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