spi clock unavailable stm32f0

Question

I have a problem while doing the configuration of the SPI on my stm32f051r8. Indeed, I've written the hole initialization code but I can't see the the clock with a scope... I just try to configure PB13 with the alternate function as a clock but it doesn't work..

Can you help me? Thank s a lot

void spi_conf()
{

GPIO_InitTypeDef    GPIO_InitStructure;
SPI_InitTypeDef   SPI_InitStructure;

/* Enable SPI clock, SPI1 */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2,ENABLE);



 /* SPI SCK, MOSI, MISO pin configuration */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_15 | GPIO_Pin_14;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_Level_1; // 10 MHz
GPIO_Init(GPIOB, &GPIO_InitStructure);

// Configure CS pin as output floating
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOB, &GPIO_InitStructure);

GPIO_PinAFConfig(GPIOB, GPIO_PinSource13, GPIO_AF_0); // SPI1 SCK
GPIO_PinAFConfig(GPIOB, GPIO_PinSource15, GPIO_AF_0); // SPI1 MOSI
GPIO_PinAFConfig(GPIOB, GPIO_PinSource14, GPIO_AF_0); // SPI1 MISO

/* SPI configuration -------------------------------------------------------     */
SPI_I2S_DeInit(SPI2);
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_Soft;
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;

SPI_Init(SPI2, &SPI_InitStructure);
SPI_SSOutputCmd(SPI2, ENABLE);
SPI_Cmd(SPI2, ENABLE);
}

int main(void)
{
spi_conf();

while(1)
{
}
}

as @duskwuff answered, you wont see anythyng on SCK pin until you send/recieve data. So you've got corrrect answer. Please, vote the answer and mark this question solved. — Bulkin

Unknown Unknown · Accepted Answer · 2015-12-08T08:09:36

The SCK pin is only clocked when data is being transmitted over SPI. Since your code doesn't transmit any data, nothing will show up on the oscilloscope.

If you want to test SPI on your board, consider adding something along the lines of:

SPI_I2S_SendData(SPI2, 0xA5);
delay_ms(100);

to your loop at the end. Now you should see some data being transmitted periodically.

spi clock unavailable stm32f0

2 Answers