Sensor über SPI auslesen STM32F4

#include "stm32f4xx.h"

#include "stm32f4_discovery.h"

void init_SPI1(void){

  GPIO_InitTypeDef GPIO_InitStruct;

  SPI_InitTypeDef SPI_InitStruct;

  // enable clock for used IO pins

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

  /* configure pins used by SPI1

   * PA5 = SCK

   * PA6 = MISO

   * PA7 = MOSI

   */

  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_6 | GPIO_Pin_5;

  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;

  GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;

  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;

  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;

  GPIO_Init(GPIOA, &GPIO_InitStruct);

  // connect SPI1 pins to SPI alternate function

  GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_SPI1);

  GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_SPI1);

  GPIO_PinAFConfig(GPIOA, GPIO_PinSource7, GPIO_AF_SPI1);

  // enable clock for used IO pins

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);

  /* Configure the chip select pin

     in this case we will use PE7 */

  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_7;

  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT;

  GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;

  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;

  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;

  GPIO_Init(GPIOE, &GPIO_InitStruct);

  GPIOE->BSRRL |= GPIO_Pin_7; // set PE7 high

  // enable peripheral clock

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);

  /* configure SPI1 in Mode 0

   * CPOL = 0 --> clock is low when idle

   * CPHA = 0 --> data is sampled at the first edge

   */

  SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex; // set to full duplex mode, seperate MOSI and MISO lines

  SPI_InitStruct.SPI_Mode = SPI_Mode_Master;     // transmit in master mode, NSS pin has to be always high

  SPI_InitStruct.SPI_DataSize = SPI_DataSize_16b; // one packet of data is 8 bits wide

  SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low;        // clock is low when idle

  SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge;      // data sampled at first edge

  SPI_InitStruct.SPI_NSS = SPI_NSS_Soft | SPI_NSSInternalSoft_Set; // set the NSS management to internal and pull internal NSS high

  SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4; // SPI frequency is APB2 frequency / 4

  SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;// data is transmitted MSB first

  SPI_Init(SPI1, &SPI_InitStruct);

  SPI_Cmd(SPI1, ENABLE); // enable SPI1

}

/* This funtion is used to transmit and receive data

 * with SPI1

 *       data --> data to be transmitted

 *       returns received value

 */

uint16_t SPI1_send(uint16_t data){

  SPI1->DR = data; // write data to be transmitted to the SPI data register

  while( !(SPI1->SR & SPI_I2S_FLAG_TXE) ); // wait until transmit complete

  while( !(SPI1->SR & SPI_I2S_FLAG_RXNE) ); // wait until receive complete

  while( SPI1->SR & SPI_I2S_FLAG_BSY ); // wait until SPI is not busy anymore

  return SPI1->DR; // return received data from SPI data register

}

int main(void)

{

  /* Initialize system */

  SystemInit();

  init_SPI1();

  uint16_t data=0;

  while(1) {

    //activate slave with LOW, disable with HIGH

    GPIOE->BSRRH |= GPIO_Pin_7; // set PE7 (CS) low

    data = SPI1_send(0x3FFF); // 0x3FFF -> Transmit Angle Read command

    GPIOE->BSRRL |= GPIO_Pin_7; // set PE7 (CS) high

    for(int i=0;i<8000000;i++);

  }

}