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I'm trying to get an SPI connection between two of the above mentioned Boards to work.

The Master seems to work well, I am using a timer Interrupt to periodically send 8bit Information "0xA5". That's what I can confirm at the MOSI Pin with an Oscilloscope. That's basically everything the Master does in my test setup.

I will now include the Initializing Code for the Slave:

void mainInit(void)

 // System Initialisierung
 SystemInit();


 // Strukturen anlegen
 RCC_ClocksTypeDef RCC_Clocks; // Struktur für Clocks anlegen (optional)
 GPIO_InitTypeDef GPIO_InitStructure;
 SPI_InitTypeDef SPI_InitStructure; //Struktur für SPI. SS: PA8; MOSI:PA7, MISO:PA6; CLK:PA5
 NVIC_InitTypeDef NVIC_InitSPI1;



 // Auslesen der Clocks und Speichern in der Struktur
 RCC_PCLK2Config(RCC_HCLK_Div16); // Timer Clock teilen
 RCC_GetClocksFreq(&RCC_Clocks); // (optional)



 // Enable Clock für Port A, Alternate Functions, SPI1 und Timer2
 RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
 RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
 RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);
 RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);


 // Interrupt Initialisieren mit SPI1
 NVIC_InitSPI1.NVIC_IRQChannel = SPI1_IRQn;
 NVIC_InitSPI1.NVIC_IRQChannelCmd = ENABLE;
 NVIC_InitSPI1.NVIC_IRQChannelPreemptionPriority = 0x0F;
 NVIC_InitSPI1.NVIC_IRQChannelSubPriority = 0x0F;
 NVIC_Init(&NVIC_InitSPI1);


 // Initialisierung CLK PA5
 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;
 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
 GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
 GPIO_Init(GPIOA, &GPIO_InitStructure);


 // Initialisierung MOSI PA7
 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
 GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
 GPIO_Init(GPIOA, &GPIO_InitStructure);


 // Initialisierung MISO PA6
 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
 GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
 GPIO_Init(GPIOA, &GPIO_InitStructure);


 // Initialisierung SS PA8
 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;
 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
 GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
 GPIO_Init(GPIOA, &GPIO_InitStructure);


 // Initialisierung Toggle pin
 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
 GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
 GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
 GPIO_Init(GPIOA, &GPIO_InitStructure);



 // Initialisierung SPI. SPI Write ist in Funktion "TIM2_IRQHandler" in stm32f1xx_it.c
 SPI_I2S_DeInit (SPI1); // Einmal deinitialisieren
 SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;
 SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
 SPI_InitStructure.SPI_CRCPolynomial = 7;
 SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
 SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
 SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
 SPI_InitStructure.SPI_Mode = SPI_Mode_Slave;
 SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;

 // SPI1 Enable
 SPI_Init(SPI1, &SPI_InitStructure);
 SPI_Cmd(SPI1, ENABLE);

 SPI_I2S_ITConfig(SPI1, SPI_I2S_IT_RXNE, ENABLE); // RXNE Interrupt Enable
 //SPI_I2S_ITConfig(SPI1, SPI_I2S_IT_TXE, ENABLE); // TXE Interrupt Enable

The pins are connected between the Master and the Slave as following:
* MOSI to MOSI (Pin A7),
* MISO to MISO(Pin A6),
* CLK to CLK (Pin A5),
* CS to CS (PinA8).

MOSI, MISO and CLK are the assigned Pins for SPI1 on the board, but I am using a custom Pin for CS. CS is always pulled to LOW by the Master just before the Transmission begins.

Since I want to work with the SPI Interrupt, when the RXNE Flag is set, I am assuming that the RXNE is never set. But I can't figure out why.
I will also show you the interrupt Routine, but since the Interrupt Routine is never called by the µC, the problem should be elsewhere.

void SPI1_IRQHandler(void)
 if(GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_8) == Bit_RESET)
 if (SPI_I2S_ReceiveData(SPI1) == 0xA5)
 GPIO_WriteBit(GPIOA, GPIO_Pin_10, Bit_SET);
 
 

Thanks for your help and if you need additional information, just let me know.

/* Edit */
I just found out, that my configuration works on a single board. So when I just Connect MOSI to MISO on one board, it runs perfectly. So, do you guys have any hint on where I mess up when it comes to a Master - Slave Connection with two boards?

Do you know the meaning of MOSI and MISO?
MOSI: Master OUT Slave IN.
MISO: Master IN Slave OUT.
Try if this connection is working.

Are the mosi and miso pins configured as Alternative function? How is "GPIO_Mode_IN_FLOATING" defined?

Please initialize your structures with 0 to be sure the configuration is clear.