Configure STM32F4 Discovery as SPI slave?

[flukeco]

Posted on July 02, 2014 at 03:20

Hi,

I want to haveSTM32F4 Discovery as SPI slave and PIC18F2580 as SPI master. I tried to modify examples found on the internet to suit my need, but none of them work. I haveneither access to oscilloscope nor logic analyzer, so it's very difficult for me to understand why the code doesn't work. The following is configuration I'm using for PIC (Master mode): Note: I used this configuration for mastertomake communicationbetween 2 PICs and it worked.

/* SMP: Sample bit 
* SPI Master mode: 
* 1 = Input data sampled at end of data output time 
* 0 = Input data sampled at middle of data output time 
* SPI Slave mode: 
* SMP must be cleared in slave mode 
*/
#define _SMP 0 
/* CKE: SPI Clock Select bit 
* 1 = Transmit occurs on transition from active to idle clock state 
* 0 = Transmit occurs on transition from idle to active clock state 
*/
#define _CKE 0 
/* CKP: Clock Polarity Select bit 
* 1 = Idle state for clock is a high level 
* 0 = Idle state for clock is a low level 
*/
#define _CKP 1 
/* Synchronous Serial Port Mode Select bits 
* 0101 = Slave mode, clock = SCK pin, SS pin disabled (can be used as I/O pin) 
* 0100 = Slave mode, clock = SCK pin, SS pin enabled 
* 0011 = Master mode, clock = TMR2 output/2 
* 0010 = Master mode, clock = Fosc/64 
* 0001 = Master mode, clock = Fosc/16 
* 0000 = Master mode, clock = Fosc/4 
*/
#define _SSPM_MASTER 0b0000 
void
SPI_init() { 
TRISA = 0x00; 
/* set all port A pins as output pins */
ADCON1 = 0x0F; 
/* set all port A pins, including SS (RA5), as digital I/O */
TRISC = 0b00010000; 
/* Set SCK pin (RC3) as output 
* SDI pin (RC4) as input 
* SDO pin (RC5) as output */
SSPSTAT = 0b00000000; 
/* Initialize SSPSTAT register to POR state */
SSPSTATbits.SMP = _SMP; 
/* Configure sample bit */
SSPSTATbits.CKE = _CKE; 
/* Configure clock select bit */
SSPCON1 = 0b00000000; 
/* Initialize SSPCON1 register to POR state */
SSPCON1bits.CKP = _CKP; 
/* Configure clock polarity select bit */
SSPCON1bits.SSPEN = 1; 
/* Enable SPI (set SCK, SDO, SDI, and SS as serial port pins)*/
SSPCON1bits.SSPM = _SSPM_MASTER; 
/* Configure sync mode bits for master */
}

And this is theconfiguration I'm using for STM32F4 Discovery (Slave mode):

void
init_SPI1(
void
) { 
GPIO_InitTypeDef GPIO_InitStruct; 
SPI_InitTypeDef SPI_InitStruct; 
// enable clock for used IO pins 
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE); 
/* configure pins used by SPI1 
* PA5 = SCK 
* PA6 = MISO 
* PA7 = MOSI 
*/
GPIO_InitStruct.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_6 | GPIO_Pin_5; 
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(GPIOA, &GPIO_InitStruct); 
// 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); 
// enable clock for used IO pins 
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE); 
// enable peripheral clock 
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE); 
/* 
* CPOL = 1 --> clock is high 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; 
// transmit in slave mode 
SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b; 
// one packet of data is 8 bits wide 
SPI_InitStruct.SPI_CPOL = SPI_CPOL_High; 
// clock is high when idle 
SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge; 
// data sampled at first edge 
SPI_InitStruct.SPI_NSS = SPI_NSS_Soft; 
// set the NSS management to internal and pull internal NSS high 
SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_LSB;
// data is transmitted MSB first 
SPI_Init(SPI1, &SPI_InitStruct); 
SPI_Cmd(SPI1, ENABLE); 
// enable SPI1 
}

I'm connecting - SCK (PA5) to PIC's SCK (RC3) - MISO (PA6) to PIC's SDI (RC4) - MOSI (PA7) to PIC's SDO (RC5) Any help would be highly appreciated. Thank you in advance for your suggestions and sorry for my bad English. Best Regards, Pat