SPI malfunction for sending data in slave mode

[dschuethe9]

Posted on December 11, 2009 at 07:27

SPI malfunction for sending data in slave mode

[janvi]

Posted on May 17, 2011 at 13:33

If your hardware NSS does not behave like expected read this thread:

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http://www.st.com/mcu/forums-cat-7032-html

[dschuethe9]

Posted on May 17, 2011 at 13:33

I have the dev. board STM32-P103 from Olimex with the STM32F103RB chip on it.

I want to connect the board via SPI to another MCU using the UEXT socket(where SPI1) is connected.

My problem is, that i can read data from the other MCU, as long as i am not loading data into the DR(SPI1) of stm32. The settings for SPI1 are the same as for the other MCU (CPOL and CPOH), the stm is programmed to slave mode with hardware nss. If i send data , i.e writing data to the DR register, there is something put out at the MISO, but totally wrong. E.g. if i write 0xaa to DR, i get on the scope either 0x3f(after reset for the first write) and 0xff for every following write. If I put 0x00 it is working as well as 0xff. But every other value is like a random output. Values to 0x04 are just 0x00(outputted).

I also tried it with the SPI2, but there I have the same problem. I thought that it has to do something with the SD cardreader which is connected to SPI2, but now with SPI1 the problem remains.

Anybody who can help me?

CODE:

#include ''stm32f10x.h''

#include

void clock_init(void);

void spi_settings(void);

void GPIO_Configuration(void)

{

GPIO_InitTypeDef GPIO_InitStructure;

/* Configure SPI1 pins: SCK, MISO and MOSI */

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_Init(GPIOA, &GPIO_InitStructure);

/* Configuration of NSS pin */

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;

GPIO_Init(GPIOA, &GPIO_InitStructure);

}

int main(void)

{

/*

@funtcion variables

*/

int repeat = 0, i=0;

u8 ReceivedData[4][4]={{0x01 , 0x02, 0x03 , 0x04},

{0x05 , 0x06, 0x07 , 0x08},

{0x09 , 0x10, 0x11 , 0x12},

{0x13 , 0x14, 0x15 , 0x16}};

u8 *pData;

clock_init();

//setting the peripheral clocks

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_SPI1, ENABLE);

GPIO_Configuration();

spi_settings();

/*

@reading from MCU

*/

while(i

{

pData= &ReceivedData[i][0];

while(repeat < 4)

{

while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);

// Send SPI1 data

SPI_I2S_SendData(SPI1, 0x55);

//checks if the transmit buffer is empty

while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE));

//read data from receive register

pData[repeat] = SPI_I2S_ReceiveData(SPI1);

repeat++;

}

repeat=0;

i++;

}

i=0;

repeat=0;

for(i=0 ; i

{

for(repeat=0; repeat

printf(''%X'', ReceivedData[i][repeat]);

printf(''\n'');

}

return 0;

}

/*****************

@ clock_init

@ initializaton of the internal clocks to System Clock = 64MHz

*****************/

void clock_init(void)

{

RCC_DeInit(); //Resets the Clock registers to default reset state

RCC_HSICmd(ENABLE); //Enable the internal 8MHz Oscillator

while(RCC_GetFlagStatus(RCC_FLAG_HSIRDY)== RESET); //wait till the HSI is ready

RCC_SYSCLKConfig(RCC_SYSCLKSource_HSI); //using internal 8MHz RC as system clock

RCC_PLLConfig(RCC_PLLSource_HSI_Div2, RCC_PLLMul_14); //Maximum frequency using internal RC->56MHz

RCC_PLLCmd(ENABLE); //enable the pll clock

while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY)== RESET);

RCC_PCLK1Config(RCC_HCLK_Div2); //set APB1 Clock to AHB/2=28MHz APB1 max = 36MHz

RCC_PCLK2Config(RCC_HCLK_Div1); //set APB2 Clock to AHB = 56MHz

RCC_HCLKConfig(RCC_SYSCLK_Div1); //set the AHB clock = system clock

#ifdef EMB_FLASH

// 5. Init Embedded Flash

// Zero wait state, if 0 < HCLK 24 MHz

// One wait state, if 24 MHz < HCLK 56 MHz

// Two wait states, if 56 MHz < HCLK 72 MHz

// Flash wait state

FLASH_SetLatency(FLASH_Latency_2);

// Half cycle access

FLASH_HalfCycleAccessCmd(FLASH_HalfCycleAccess_Disable);

// Prefetch buffer

FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);

#endif // EMB_FLASH

RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK); //using internal PLL = 56MHz

}

/*************

@ spi_settings

@ sets the spi peripheral to pins PB12...15, SPI1

************/

void spi_settings(void)

{

SPI_InitTypeDef SPI_InitStructure; //Struct for Init the SPI1

SPI_I2S_DeInit(SPI1); // Deinitialization of SPI1

/* setting the wanted setup for SPI1---------------------------------*/

SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;

SPI_InitStructure.SPI_Mode = SPI_Mode_Slave;

SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;

SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low; // Clock idle state - LOW

SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge; //data is captured on the 2nd edge

SPI_InitStructure.SPI_NSS = SPI_NSS_Hard; // chip select done by hardware

SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8; //Irrelevant in slave mode SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;

/*-------------------------------------------------------------------*/

SPI_Init(SPI1, &SPI_InitStructure); //INIT the SPI Interface

SPI_SSOutputCmd(SPI1, DISABLE); // enable NSS pin as output

SPI_Cmd(SPI1, ENABLE); //Enables the SPI1 peripherial

}