SPI Problem(NO SCK Signal when receiving)

[andykim]

Posted on May 15, 2013 at 05:08

Hi, everyone.

I am trying to control a slave device by SPI Communication. But I have a problem with SPI, SCK is not output when receiving a data. Tx is OK. Why does this problem happen? I hope you help me to slove this problem. The belowing is my code

void bsp_init_rcc(void)

{   /* SYSCLK, HCLK, PCLK2 and PCLK1 configuration -----------------------------*/    /* RCC system reset(for debug purpose) */  RCC_DeInit();    /* Enable HSE */  RCC_HSEConfig(RCC_HSE_ON);    /* Wait till HSE is ready */  HSEStartUpStatus = RCC_WaitForHSEStartUp();    ..................................................  /* Enable GPIOA, GPIOB, GPIOC, GPIOD, GPIOE and AFIO clocks */  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB |RCC_APB2Periph_GPIOC | RCC_APB2Periph_GPIOD | RCC_APB2Periph_GPIOE | RCC_APB2Periph_AFIO, ENABLE);          /* Enable peripheral clocks --------------------------------------------------*/  /* SPI1 clock enable */  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);    /* SPI2 Periph clock enable */  RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE); }

void bsp_init_gpio(void)

{  GPIO_InitTypeDef GPIO_InitStructure;     /* Configure SPI1 pins: SCK, MISO and MOSI ---------------------------------*/  /* Confugure NSS, SCK and MOSI pins as Alternate Function Push Pull */  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_7;  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  GPIO_Init(GPIOA, &GPIO_InitStructure);    /* Confugure MISO pin as Input Floating  */  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;  GPIO_Init(GPIOA, &GPIO_InitStructure);

 /* Confugure NSS pin as Output  */

 GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_4 ;  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;  GPIO_Init(GPIOA, &GPIO_InitStructure);  }

void spi_init(void)

{   /* SPI1 configuration ------------------------------------------------------*/   SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;   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_Hard;   SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4;   SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;   SPI_InitStructure.SPI_CRCPolynomial = 7;   SPI_Init(SPI1, &SPI_InitStructure);     /* Enable SPI1 CRC calculation */   SPI_CalculateCRC(SPI1, ENABLE);

 SPI_SSOutputCmd(SPI1, ENABLE);

 /* Enable SPI1 */

  SPI_Cmd(SPI1, ENABLE);    SPI_NSS_High(); }

void SPI_tx_data(uint8_t data)

{   /* Wait for SPI1 Tx buffer empty */   while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);

 SPI_NSS_Low();

  SPI_I2S_SendData(SPI1, data);  while(SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_BSY) == SET) ;  SPI_NSS_High(); }

uint8_t SPI_rx_data(void)

{  uint8_t data;

 /* Wait for SPI1 data reception */

 while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);    SPI_NSS_Low();   data = SPI_I2S_ReceiveData(SPI1);  SPI_NSS_High();    return data; } Please help me

[Tesla DeLorean]

Posted on May 15, 2013 at 06:21

Why does this problem happen?

Because the bus is symmetrical, as a Master device it clocks out on one edge, and back on the other. ReceiveData just reads a holding register, it does not clock. You'll need to send a junk/dummy byte to generate the clocks to load the receive register.

[andykim]

Posted on May 15, 2013 at 07:11

Hi clive1

Do you mean the folllowing coding?

uint8_t SPI_rx_data(void)

{  uint8_t data;  SPI_NSS_Low();   SPI_I2S_SendData(SPI1, 0x00);  while(SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_BSY) == SET) ;  SPI_NSS_High();    /* Wait for SPI1 data reception */  while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);

  data = SPI_I2S_ReceiveData(SPI1);

 return data; } By a dummy byte tx, I can see a data output from the slave device. But I cann't read the recevied data at the data register of the STM32F103, which is received from the slave. How can I do this? Thanks clive1.