STM32F429I-discovery SPI Troubles

[shan_rei]

Posted on January 12, 2014 at 07:43

Hi, I just received my STM32F429 discovery board and I tried to implement basic SPI but I'm stumped as to why the logic analyzer output was different. Can anybody point out were I was wrong. Here is the code.

#include <stm32f4xx.h>

#include <stm32f4xx_gpio.h>

#include <stm32f4xx_rcc.h>

#include <stm32f4xx_spi.h>



void
spi1_init(
void
);

void
spiSend(uint8_t data);

uint8_t spiRead(
void
);

void
csInit(
void
);


uint8_t txBuffer[4] = {0x00, 0x01, 0x02, 0x03};

uint8_t rxBuffer[4];


void
Delay(__IO uint32_t nCount){

while
(nCount--)

{

}

}


int
main(
void
){


int
i,j;


csInit();

spi1_init();


for
(i = 0; i < 4; i++){

GPIO_WriteBit(GPIOE, GPIO_Pin_3, 0);

spiSend(txBuffer[i]);

rxBuffer[i] = spiRead();

GPIO_WriteBit(GPIOE, GPIO_Pin_3, 1);

}


while
(1){

}


}


void
csInit(
void
){


GPIO_InitTypeDef GPIO_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);


/* Configure chip select pin to PE3 */

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;

GPIO_Init(GPIOE, &GPIO_InitStructure);


GPIO_WriteBit(GPIOE, GPIO_Pin_3, 1); 
/* Set chip select high */

}

void
spi1_init(
void
){

GPIO_InitTypeDef GPIO_InitStructure;

SPI_InitTypeDef SPI_InitStructure;


RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);


/* Configure GPIO pins for SPI1 

* PA5 = SCK

* PA6 = MISO

* PA7 = MOSI

*/


GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_6 | GPIO_Pin_5;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_Init(GPIOA, &GPIO_InitStructure);


/* 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);


/* Configure SPI1 */

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_64;

SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;

SPI_InitStructure.SPI_CRCPolynomial = 7;


SPI_Init(SPI1, &SPI_InitStructure);

SPI_Cmd(SPI1, ENABLE);

}


void
spiSend(uint8_t data){

while
(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE));

SPI_I2S_SendData(SPI1, data);


}


uint8_t spiRead(
void
){

while
(SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);

return
SPI_I2S_ReceiveData(SPI1);


}


#ifdef USE_FULL_ASSERT

void
assert_failed(uint8_t * file, uint32_t line){

while
(1)

{


}

}

#endif

And here is the output of the logic analyzer. Thank you very much! #discovery #stm32f429 #spi

[Tesla DeLorean]

Posted on January 12, 2014 at 13:24

I might start by initializing PE3 properly. Tip: Don't enable line numbers unless you specifically use them to refer to something.

void csInit(void){
 
 GPIO_InitTypeDef GPIO_InitStructure;
 RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);
 
 /* Configure chip select pin to PE3 */
 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
 GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
 GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
 GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
 GPIO_Init(GPIOE, &GPIO_InitStructure);
 
 GPIO_WriteBit(GPIOE, GPIO_Pin_3, 1); /* Set chip select high */
}

[shan_rei]

Posted on January 12, 2014 at 17:20

Thank you very much clive1! So now I properly configured the select pin. But I now got the following result from the logic analyzer...it seems the values that are sent are being doubled. What have I done wrong now?

Thank you.

[Tesla DeLorean]

Posted on January 12, 2014 at 18:23

Perhaps because the analyzer chooses to use the falling edge of the clock, and not the rising edge?

[a_rocchegiani]

Posted on January 13, 2014 at 00:02

I think the logic analyzer trigger as first clock pulse the 'glitch' generated between GPIO_Init() and GPIOA_Config() so the data are shifted left by 1 bit.

Try to set all used GPIO pins to 1 before to call GPIO_Init() either in csInit() and spi1Init() using GPIO_Setbits()  or GPIO_Write() so when you initialize the port in output mode, the respective bits in ODR are already set. 

[shan_rei]

Posted on January 18, 2014 at 16:27

Hello 

a.rocchegiani! I did what you suggested  and still got the same output.

Would you think that using a different operating system might affect my output? Since I rolled my own toolchain, I'm beginning to think that I might have done something wrong in the configuration of the toolchain that I am using. I'll try to compile this code again using Keil and see if I still get the same output. Thanks for the tips and suggestions.