Question
SPI loop-back test - STM32F3
Posted on May 08, 2013 at 14:48
Hey all, I've been trying to get SPI working on my STM32F3 discovery board recently but it just doesn't seem to be working. I was hoping to test it in loop-back configuration and display the sent data on the board LEDs just to check if it was working, but no luck so far.UnfortunatelyI don't have a scope handy to check the signals either.
Here's the code and configuration I've written:/* Includes ------------------------------------------------------------------*/
#include ''main.h''
/* variables ---------------------------------------------------------*/
GPIO_InitTypeDef GPIO_InitStructure;
SPI_InitTypeDef SPI_InitStructure;
/* function prototypes -----------------------------------------------*/
void
delay(
int
);
void
GPIO_cfg(
void
);
void
SPI_GPIO_init(
void
);
void
SPI_init(
void
);
int
main(
void
)
{
uint8_t test_data = 0xAF;
uint8_t rxbuf;
GPIO_cfg();
SPI_GPIO_init();
SPI_init();
while
(1){
// Assert /CS followed by delay
GPIO_ResetBits(GPIOA, GPIO_Pin_4);
delay(10);
while
(SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE == 0) );
// Wait for TX buffer to be not empty. ie data loaded
SPI_SendData8(SPI1, test_data);
// Send data
while
(SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE == 0) );
//wait for last bit to be sent
rxbuf = SPI_ReceiveData8(SPI1);
// Receive data
// Deassert /CS after delay
delay(10);
GPIO_ResetBits(GPIOA, GPIO_Pin_4);
GPIO_SetBits(GPIOE, rxbuf<<8);
// shift result up 8 bits to display on LEDs
delay(400);
}
}
void
delay(
int
n){
int
i,l;
for
(i=0; i<n; i++){
for
(l=0; l<n; l++){}
}
}
/* GPIO configuration for LEDs */
void
GPIO_cfg(){
// Configure/enable peripheral clocks
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOE, ENABLE);
/* Configure PE15 in output pushpull mode */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_All;
// GPIO_Pin_all to address all pins
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOE, &GPIO_InitStructure);
}
/* Set up GPIO for SPI */
void
SPI_GPIO_init(){
//Disable SPI
SPI_I2S_DeInit(SPI1);
// Enable clock for SPI 1
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);
// Enable Clock for SPI GPIOA
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
// Set up SCLK, MISO and MOSI pins
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7;
// Select pins ( SCLK | MISO | MOSI)
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
// Set as AF mode
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOA, &GPIO_InitStructure);
// Configure GPIO Alternate function as SPI1
GPIO_PinAFConfig(GPIOA, GPIO_Pin_5, GPIO_AF_5);
// SPI1 SCLK
GPIO_PinAFConfig(GPIOA, GPIO_Pin_6, GPIO_AF_5);
// SPI1 MISO
GPIO_PinAFConfig(GPIOA, GPIO_Pin_7, GPIO_AF_5);
// SPI1 MOSI
// Set up CS pin
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
// OType, Speed and PuPd are the same
GPIO_Init(GPIOA, &GPIO_InitStructure);
}
/* Set up SPI and related parameters */
void
SPI_init(){
// Configure SPI
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_32;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_InitStructure.SPI_CRCPolynomial = 7;
SPI_Init(SPI1, &SPI_InitStructure);
// Enable SPI1
SPI_Cmd(SPI1, ENABLE);
// ensure RXNE is initially clear
SPI_ReceiveData8(SPI1);
}