why i get wrong data of pitch and roll angle ?

[PINI BITON]

Posted on December 21, 2016 at 22:00

i have question about accelerometer of stm32f4 LIS302dl version 

why i get wr

ong data of  pitch and roll angle ?

 mySPI_SendData(0x20,0xC7); //LIS302D Config

acc_pitch = atan2(acc_x, -acc_z)*180/M_PI;

acc_roll = -atan2(acc_y, -acc_z)*180/M_PI;

uint8_t mySPI_GetData(uint8_t adress)

{

GPIO_ResetBits(GPIOE, GPIO_Pin_3);

adress = 0x80 | adress;

while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE)); //transmit buffer empty?

SPI_I2S_SendData(SPI1, adress);

while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE)); //data received?

SPI_I2S_ReceiveData(SPI1); //Clear RXNE bit

while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE)); //transmit buffer empty?

SPI_I2S_SendData(SPI1, 0x00); //Dummy byte to generate clock

while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE)); //data received?

GPIO_SetBits(GPIOE, GPIO_Pin_3);

return SPI_I2S_ReceiveData(SPI1); //return reveiced data

}

void mySPI_SendData(uint8_t adress, uint8_t data){

GPIO_ResetBits(GPIOE, GPIO_Pin_3);

while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE)); //transmit buffer empty?

SPI_I2S_SendData(SPI1, adress);

while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE)); //data received?

SPI_I2S_ReceiveData(SPI1);

while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE)); //transmit buffer empty?

SPI_I2S_SendData(SPI1, data);

while(!SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE)); //data received?

SPI_I2S_ReceiveData(SPI1);

GPIO_SetBits(GPIOE, GPIO_Pin_3);

}

void mySPI_Init(void)

{

RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);

SPI_InitTypeDef SPI_InitTypeDefStruct;

SPI_InitTypeDefStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_2; // SPI frequency is APB2 frequency / 2

SPI_InitTypeDefStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex; // set to full duplex mode, seperate MOSI and MISO lines

SPI_InitTypeDefStruct.SPI_Mode = SPI_Mode_Master; // transmit in master mode, NSS pin has to be always high

SPI_InitTypeDefStruct.SPI_DataSize = SPI_DataSize_8b; // one packet of data is 8 bits wide

SPI_InitTypeDefStruct.SPI_NSS = SPI_NSS_Soft; // set the NSS management to internal and pull internal NSS high

SPI_InitTypeDefStruct.SPI_FirstBit = SPI_FirstBit_MSB; // data is transmitted MSB first

SPI_InitTypeDefStruct.SPI_CPOL = SPI_CPOL_High; // clock is low when idle

SPI_InitTypeDefStruct.SPI_CPHA = SPI_CPHA_2Edge; // data sampled at first edge

//SPI_InitTypeDefStruct.SPI_CRCPolynomial

SPI_Init(SPI1, &SPI_InitTypeDefStruct);//Initializes function according to above

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA | RCC_AHB1Periph_GPIOE , ENABLE);

GPIO_InitTypeDef GPIO_InitTypeDefStruct;

/* configure pins used by SPI1

* PA5 = SCK

* PA6 = MISO

* PA7 = MOSI

*/

GPIO_InitTypeDefStruct.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_7 | GPIO_Pin_6;

GPIO_InitTypeDefStruct.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitTypeDefStruct.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitTypeDefStruct.GPIO_OType = GPIO_OType_PP;

GPIO_InitTypeDefStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_Init(GPIOA, &GPIO_InitTypeDefStruct);//Initializes function according to above

// Configure the chip select pin

GPIO_InitTypeDefStruct.GPIO_Pin = GPIO_Pin_3;

GPIO_InitTypeDefStruct.GPIO_Mode = GPIO_Mode_OUT;

GPIO_InitTypeDefStruct.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitTypeDefStruct.GPIO_PuPd = GPIO_PuPd_UP;

GPIO_InitTypeDefStruct.GPIO_OType = GPIO_OType_PP;

GPIO_Init(GPIOE, &GPIO_InitTypeDefStruct);//Initializes function according to above

GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_SPI1);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_SPI1);

GPIO_PinAFConfig(GPIOA, GPIO_PinSource7, GPIO_AF_SPI1);

GPIO_SetBits(GPIOE, GPIO_Pin_3);

SPI_Cmd(SPI1, ENABLE);

}

void InitializeLEDs()

{

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);

GPIO_InitTypeDef GPIO_InitTypeDefStruct;

/*Configure GPIO pins : LED1_Pin LED2_Pin LED3_Pin LED4_Pin */

GPIO_InitTypeDefStruct.GPIO_Pin = GPIO_Pin_12 |GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15 ;

GPIO_InitTypeDefStruct.GPIO_Mode = GPIO_Mode_OUT;

//GPIO_InitTypeDefStruct.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitTypeDefStruct.GPIO_OType = GPIO_OType_PP;

GPIO_InitTypeDefStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;

GPIO_InitTypeDefStruct.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOD, &GPIO_InitTypeDefStruct);

}

[AvaTar]

Posted on December 22, 2016 at 07:47

why i get wr

ong data of  pitch and roll angle ?

 mySPI_SendData(0x20,0xC7); //LIS302D Config

acc_pitch = atan2(acc_x, -acc_z)*180/M_PI;

acc_roll = -atan2(acc_y, -acc_z)*180/M_PI;

I might guess it has to do with parameters and data types.

The

atan2

function, like most other trigonometric

libm

functions, take double parameters which are expected to be radians. But the

acc_x, acc_y and acc_z

are

unsigned short

, aren't they ?

BTW, you can verify such calculations and algorithms easily on a PC, using a generic toolchain + debugger. I would even recommend it.