Posted on June 13, 2013 at 11:08hi,
I am working on a project where I need to sample some data using the ADC in discovery at 1MSPs and transfer it to a raspberry pi board via SPI. As Rpi supports only SPI master mode the discovery board acts as a slave.However I am not able to get the discovery board work in slave mode. I am posting it a sample program I used to test spi in discovery board .
&sharpinclude <stm32f4xx.h>
&sharpinclude <stm32f4xx_spi.h>
uint8_t SPI1_send(uint8_t data);
// this function initializes the SPI1 peripheral
void init_SPI1(void){
GPIO_InitTypeDef GPIO_InitStruct;
SPI_InitTypeDef SPI_InitStruct;
// enable clock for used IO pins
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
/* configure pins used by SPI1
* PA5 = SCK
* PA6 = MISO
* PA7 = MOSI
*/
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOB, &GPIO_InitStruct);
// connect SPI1 pins to SPI alternate function
GPIO_PinAFConfig(GPIOB, GPIO_PinSource13, GPIO_AF_SPI2);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource14, GPIO_AF_SPI2);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource15, GPIO_AF_SPI2);
// enable clock for used IO pins
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);
// enable peripheral clock
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);
/* configure SPI1 in Mode 0
* CPOL = 0 --> clock is low when idle
* CPHA = 0 --> data is sampled at the first edge
*/
SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex; // set to full duplex mode, seperate MOSI and MISO lines
SPI_InitStruct.SPI_Mode = SPI_Mode_Slave;
SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b; // one packet of data is 8 bits wide
SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low; // clock is low when idle
SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge; // data sampled at first edge
SPI_InitStruct.SPI_NSS = SPI_NSS_Soft | SPI_NSSInternalSoft_Set; // set the NSS management to internal and pull internal NSS high
SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_2; // SPI frequency is APB2 frequency / 4
SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;// data is transmitted MSB first
SPI_Init(SPI2, &SPI_InitStruct);
SPI_Cmd(SPI2, ENABLE); // enable SPI1
}
/* This funtion is used to transmit and receive data
* with SPI1
* data --> data to be transmitted
* returns received value
*/
uint8_t SPI2_recv(){
uint8_t temp ;
while( !(SPI2->SR & SPI_I2S_FLAG_RXNE) ); // wait until receive complete
temp = SPI2->DR ; // write data to be transmitted to the SPI data register
while( !(SPI2->SR & SPI_I2S_FLAG_TXE) ); // wait until transmit complete
while( SPI2->SR & SPI_I2S_FLAG_BSY ); // wait until SPI is not busy anymore
return temp; // return received data from SPI data register
}
&sharpif 1
int main(void){
uint8_t received_val = 0;
init_SPI1();
while(1){
received_val = SPI2_recv(); // transmit dummy byte and receive data
}
}
&sharpendif
When I debug the code I see that while( !(SPI2->SR & SPI_I2S_FLAG_RXNE) ); condition is never being met. Also how to I enable interrupts for the same?
#slave #discovery #stm32f4 #spi
