SPI Clock problem

[pranathi1091]

Posted on December 21, 2012 at 08:32

Hello ALL,

I am using stm32f2xxx. I am programing An accelerometer which is interfaced via SPI. The problem i m facing is the clock is not always continous. My HSEValue is 8Mhz. When i get the clcok properly i could see RXNE flag and TXE flag set and it receives valid data. But when i dont get the clock properly i see only TXE flag set. Below is my init, read and write codes

void GPIO_Configuration(void)

{ GPIO_InitTypeDef GPIO_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA ,ENABLE);

GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF;

GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_DOWN;

_InitStructure.GPIO_Pin=SPI1_SCK_PIN;

GPIO_Init(SPI1_GPIO_PORT,&GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin=SPI1_MOSI_PIN;

GPIO_Init(SPI1_GPIO_PORT,&GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin=SPI1_MISO_PIN;

GPIO_Init(SPI1_GPIO_PORT,&GPIO_InitStructure);

GPIO_PinAFConfig(GPIOA,SPI1_SCK_SOURCE,GPIO_AF_SPI1);

GPIO_PinAFConfig(GPIOA,SPI1_MOSI_SOURCE,GPIO_AF_SPI1); GPIO_PinAFConfig(GPIOA,SPI1_MISO_SOURCE,GPIO_AF_SPI1);

/*Configure  CS pin in output pushpull mode*/

  GPIO_InitStructure.GPIO_Pin = SPI1_CS_PIN;   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;   GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;   GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

  GPIO_Init(SPI1_GPIO_PORT, &GPIO_InitStructure);

}

void SPIConfiguration(void)

{

unsigned char ucdummy;

static char ucindex = 20;

unsigned char rxbuf[20];

void SPI_Config()

{ SPI_InitTypeDef SPI_InitStructure;

RCC_APB2PeriphClockCmd (RCC_APB2Periph_SPI1, ENABLE);

/*SPI initializations*/

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_High;  SPI_InitStructure.SPI_CPHA=SPI_CPHA_2Edge;  SPI_InitStructure.SPI_NSS=SPI_NSS_Soft; SPI_InitStructure.SPI_BaudRatePrescaler=SPI_BaudRatePrescaler_2; SPI_InitStructure.SPI_FirstBit=SPI_FirstBit_MSB; //SPI_InitStructure.SPI_CRCPolynomial=7; SPI_InitStructure.SPI_CRCPolynomial=0;

SPI_Init(SPI1,&SPI_InitStructure);

SPI_SSOutputCmd(SPI1,ENABLE); SPI_Cmd(SPI1,ENABLE); }

uint8_t SPIXLWriteData(uint8_t Add, uint16_t Data)

{ uint32_t TimeOut;

while ((SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_BSY)))

{ if (TimeOut--==0) { return SPI_ERROR; } } CS_LOW(); SPI_I2S_SendData(SPI1, ADXL345_W|Add);         while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);         ClrRcvBuf();                  SPI_I2S_SendData(SPI1, Data);         ClrRcvBuf();         while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_BSY) == SET);         CS_HIGH();

return 1;

}

uint8_t SPIReadData(uint8_t RegisterAddress, uint8_t NoOfRgisters)

{ uint32_t TimeOut; uint16_t RxBuffer; /* Select Slave*/ CS_LOW(); /*Make sure the bus is not busy*/ while ((SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_BSY))) { if (TimeOut--==0) { return SPI_TIMEOUT_ERROR; } } //RxBuffer = SPI_I2S_ReceiveData(SPI1); SPI_I2S_SendData(SPI1, XL345_R|RegisterAddress);

ClrRcvBuf();

RxBuffer=SPI_I2S_ReceiveData(SPI1); while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);         //dummy byte*/         SPI_I2S_SendData(SPI1, 0x00);                        while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);      the    RxBuffer = SPI_I2S_ReceiveData(SPI1);          while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE) != SET);        while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_BSY) == SET);                         CS_HIGH();

return  RxBuffer;

}

void SPIXLReadSequence(uint8_t reg,uint8_t count)

{         uint8_t i = 0;           CS_LOW();               SPI_I2S_SendData(SPI1, ADXL345_R | ADXL345_MB | reg);                ClrRcvBuf();                while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);                        SPI_I2S_SendData(SPI1, 0xFF);                 while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);                  data[i]= SPI_I2S_ReceiveData(SPI1);                                   i++;          }         while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_BSY) == SET);         CS_HIGH();

}

#spi

[Tesla DeLorean]

Posted on December 21, 2012 at 13:40

You have to send data for the clocks to be generated. As the transmit data clocks out, the receive data clocks in. Reading the DR just clears a flags, and provides the register content, it does not initiate a transfer. SPI_I2S_ReceiveData() just reads the DR, nothing else.

[pranathi1091]

Posted on December 24, 2012 at 05:47 Thanks clive I could get Transmit working and the clock is generated while sending data out. How do i do with the reception. If I am correct, the recent data will be in DR register and hence i read Data register. Could u pls correct me or let me what needs to be done for reception to work Thanks

[pranathi1091]

Posted on December 28, 2012 at 07:20 I could resolve the issue when i send and receive sequence of bytes. I dont have any probelm in reading a single byte from Accelreometer. But i am facing problem when i try to read multibyte data from ADXL345, which always gives 00 from all the axis.