Data is being sampled by SPI even if clock signal is not provided, when configured as slave.

Posted on September 07, 2017 at 15:40

We are using the STM32F030F4 micro-controller for our project. We need to receive the data from other STM32 micro-controller.

We are able to receive the data through SPI. However, data is being sampled even if clock is not provided ( i..e Only data line ( MOSI ) is connected, Clock is not connected ).

Below is the SPI register configuration:

CR1 Register

Register Bit parameter

Config value

Description

BIDIMODE

0

2-line unidirectional data mode

BIDIOE

0

Receive-only mode

CRCEN

0

CRC calculation disabled

CRCNEXT

0

Next transmit value is from TX buffer

CRCL

0

8-bit CRC length

RXONLY

1

Output disabled (Receive-only mode)

SSM

1

Software slave management enabled

SSI

0

LSBFIRST

0

data is received with the MSB first

SPE

1

Peripheral enabled

BR[2:0]

0

fPCLK/2

MSTR

0

Slave mode

CPOL

1

CK to 1 when idle

CPHA

1

The second clock transition is the first data capture edge

CR2 Register

Register Bit parameter

Config value

Description

DS [3:0]:

0x07

8 - bits data length for SPI transfers

Are we missing any configurations ? Could you please guide us to resolve this issue ?

Below is the SPI & GPIO initialization code:

[NOTE : The function HAL_SPI_MspInit() is getting invoked inside the HAL_SPI_Init() ]

SPI_HandleTypeDef     stSpiHandle = { 0 };  // SPI handler declaration

void SPIInit( void )

{

/* Set the SPI parameters */

   stSpiHandle.Instance = SPI1;

   stSpiHandle.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_2;

   stSpiHandle.Init.Direction                  = SPI_DIRECTION_2LINES_RXONLY;

   stSpiHandle.Init.CLKPhase               = SPI_PHASE_2EDGE;

   stSpiHandle.Init.CLKPolarity             = SPI_POLARITY_HIGH;

   stSpiHandle.Init.CRCCalculation      = SPI_CRCCALCULATION_DISABLE;

   stSpiHandle.Init.DataSize                 = SPI_DATASIZE_8BIT;

   stSpiHandle.Init.FirstBit                    = SPI_FIRSTBIT_MSB;

   stSpiHandle.Init.NSS                        = SPI_NSS_SOFT;

   stSpiHandle.Init.NSSPMode             = SPI_NSS_PULSE_DISABLE;

   stSpiHandle.Init.TIMode                   = SPI_TIMODE_DISABLE;

   stSpiHandle.Init.Mode                      = SPI_MODE_SLAVE;

   if ( HAL_SPI_Init( &stSpiHandle ) != HAL_OK )

   {

         SET_FAULT_STATUS( FAULT_SPI_CONFIG_FAILED );

   }

}

void HAL_SPI_MspInit(SPI_HandleTypeDef *hspi)

{

   GPIO_InitTypeDef GPIO_InitStruct;

   if(hspi->Instance == SPI1)

   {

      /* Enable peripherals and GPIO Clocks */

      SPI1_SCK_GPIO_CLK_ENABLE();

      SPI1_MOSI_GPIO_CLK_ENABLE();

      SPI1_CLK_ENABLE();

      /* SPI SCK GPIO pin configuration */

 GPIO_InitStruct.Mode        = GPIO_MODE_AF_PP;

 GPIO_InitStruct.Speed       = GPIO_SPEED_FREQ_HIGH;

      GPIO_InitStruct.Pin            = SPI1_SCK_PIN;

      GPIO_InitStruct.Alternate   = SPI1_SCK_AF;

      HAL_GPIO_Init(SPI1_SCK_GPIO_PORT, &GPIO_InitStruct);

      /* SPI MOSI GPIO pin configuration */

 GPIO_InitStruct.Mode        = GPIO_MODE_AF_PP;

 GPIO_InitStruct.Speed       = GPIO_SPEED_FREQ_HIGH;

      GPIO_InitStruct.Pin            = SPI1_MOSI_PIN;

      GPIO_InitStruct.Alternate   = SPI1_MOSI_AF;

      HAL_GPIO_Init(SPI1_MOSI_GPIO_PORT, &GPIO_InitStruct);

   }

}

Thanks & Regards,

Kishor   

#stm32f030-spi-clock #stm32f0-spi #spi