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stm32F2 Max Speed Master SPI

Question asked by lopez.pedro.001 on Feb 28, 2015
Latest reply on Feb 28, 2015 by lopez.pedro.001
Hi. I'm trying to set the spi at max speed (in theory 30mbit/s spi in stm32F2), but I just get 15mbits on SPI output.

This is my spi initialization (for SPI3). 

I'm using DMA to transfer a buffer, but in theory that is independent of SPI speed.

Where is my problem?

//SPI3 initialization
static void SPI_Config(void)
  GPIO_InitTypeDef GPIO_InitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;
  SPI_InitTypeDef  SPI_InitStructure;

  /* Peripheral Clock Enable -------------------------------------------------*/
  /* Enable the SPI clock */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI3, ENABLE);
  /* Enable GPIO clocks */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);

  /* SPI GPIO Configuration --------------------------------------------------*/
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource12, GPIO_AF_SPI3);
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_SPI3);

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_DOWN;

  /*!< SPI SCK pin configuration */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
  /*!< SPI MOSI pin configuration */
  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_10;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
  /* SPI configuration -------------------------------------------------------*/
  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_Low;
  SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;
  SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
  SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_2;
  SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
  SPI_InitStructure.SPI_CRCPolynomial = 7;
  SPI_Init(SPI3, &SPI_InitStructure);