Question

我是STM32世界的新手，我对STM32F429-DISC1板上的板载L3GD20陀螺仪有疑问。

我遇到麻烦让它运行（陀螺仪不断发送相同的数据，即使在重置或断电后），在我最终设法使其工作（通过发送指令几次）之后，我看到了奇怪的结果（均在x轴，y和z上）（见下图）。

我是否遗漏了某些内容，或者我应该对原始数据做些什么，这会使它顺利进行？ IC是否存在缺陷？

我正在使用Atollic TrueStudio v9.0 for STM32和STM32F429-DISC1。

这是我的代码：

#include "stm32f4xx.h"
#include "stm32f429i_discovery.h"
#include "stdio.h"
volatile uint32_t elapsed = 0;

#define CS_gyro_start   GPIO_ResetBits( GPIOC, GPIO_Pin_1 )
#define CS_gyro_stop    GPIO_SetBits( GPIOC, GPIO_Pin_1 )

void DelayMS( int time ){
    elapsed = time;
    while( elapsed > 0 );
}

void SysTick_Handler(){
    if( elapsed > 0 ) --elapsed;
}

void SendChar( char ch ){
    while( USART_GetFlagStatus( USART1, USART_FLAG_TXE ) == RESET ){}
    USART_SendData( USART1, ch );
}
void sendString( const char *s ){
    while( *s ){
        SendChar( *s++ );
    }
}
int _write( int file, char *ptr, int len ){
    sendString( ptr );
return len;
}  //sadly this doesn't work with float variables


void initialize( void ){
    RCC_AHB1PeriphClockCmd( RCC_AHB1Periph_GPIOA |
                            RCC_AHB1Periph_GPIOC |
                            RCC_AHB1Periph_GPIOF, ENABLE );

    RCC_APB2PeriphClockCmd( RCC_APB2Periph_SPI5 |
                            RCC_APB2Periph_SYSCFG |
                            RCC_APB2Periph_USART1, ENABLE );

    GPIO_InitTypeDef        gpio;
    USART_InitTypeDef       usart;
    SPI_InitTypeDef         spi;

    GPIO_StructInit(    &gpio );
    USART_StructInit(   &usart );
    SPI_StructInit(     &spi );

//usart
    GPIO_PinAFConfig( GPIOA, GPIO_PinSource10, GPIO_AF_USART1 );
    GPIO_PinAFConfig( GPIOA, GPIO_PinSource9, GPIO_AF_USART1 );

    gpio.GPIO_Mode =        GPIO_Mode_AF;
    gpio.GPIO_OType =       GPIO_OType_PP;
    gpio.GPIO_PuPd =        GPIO_PuPd_NOPULL;
    gpio.GPIO_Pin =         GPIO_Pin_9 | GPIO_Pin_10;
    GPIO_Init( GPIOA, &gpio );

    usart.USART_BaudRate =  115200;
    USART_Init( USART1, &usart );

    USART_Cmd( USART1, ENABLE );

//spi
    GPIO_PinAFConfig( GPIOF, GPIO_PinSource7, GPIO_AF_SPI5 );
    GPIO_PinAFConfig( GPIOF, GPIO_PinSource9, GPIO_AF_SPI5 );
    GPIO_PinAFConfig( GPIOF, GPIO_PinSource8, GPIO_AF_SPI5 );

    //SS
    gpio.GPIO_Pin =     GPIO_Pin_1;
    gpio.GPIO_Mode =    GPIO_Mode_OUT;
    gpio.GPIO_OType =   GPIO_OType_PP;
    gpio.GPIO_PuPd =    GPIO_PuPd_NOPULL;
    GPIO_Init( GPIOC, &gpio );
    GPIO_SetBits( GPIOC, GPIO_Pin_1 );

    //SCK, MOSI
    gpio.GPIO_Pin =     GPIO_Pin_9 | GPIO_Pin_7;
    gpio.GPIO_OType =   GPIO_OType_PP;
    gpio.GPIO_Mode =    GPIO_Mode_AF;
    gpio.GPIO_Speed =   GPIO_Speed_50MHz;
    gpio.GPIO_PuPd =    GPIO_PuPd_NOPULL;
    GPIO_Init( GPIOF, &gpio );

    //MISO
    gpio.GPIO_Pin =     GPIO_Pin_8;
    gpio.GPIO_OType =   GPIO_OType_PP;
    gpio.GPIO_Mode =    GPIO_Mode_AF;
    gpio.GPIO_Speed =   GPIO_Speed_50MHz;
    gpio.GPIO_PuPd =    GPIO_PuPd_NOPULL;
    GPIO_Init( GPIOF, &gpio );

    spi.SPI_Mode =                  SPI_Mode_Master;
    spi.SPI_NSS =                   SPI_NSS_Soft;
    spi.SPI_BaudRatePrescaler =     SPI_BaudRatePrescaler_256;
    SPI_Init( SPI5, &spi );
    SPI_Cmd( SPI5, ENABLE );

}


uint8_t SPI_sendByte( uint8_t byte_ ){
    while( SPI_I2S_GetFlagStatus( SPI5, SPI_I2S_FLAG_TXE ) == RESET ){}
    SPI_I2S_SendData( SPI5, byte_ );

    while( SPI_I2S_GetFlagStatus( SPI5, SPI_I2S_FLAG_RXNE ) == RESET ){}
return SPI_I2S_ReceiveData( SPI5 );
}

void SPI_writeData( uint8_t address, uint8_t byteToWrite ){
    CS_gyro_start;
        SPI_sendByte( address );
        SPI_sendByte( byteToWrite );
    CS_gyro_stop;
}

void GetGyroValues( uint16_t *x, uint16_t *y, uint16_t *z ){
    CS_gyro_start;
        SPI_sendByte( 0x29 | 0x80 );
        *x = SPI_sendByte( 0xff );
    CS_gyro_stop;
    CS_gyro_start;
        SPI_sendByte( 0x28 | 0x80 );
        *x |= (SPI_sendByte( 0xff ) << 8);
    CS_gyro_stop;

    CS_gyro_start;
        SPI_sendByte( 0x2B | 0x80 );
        *y = SPI_sendByte( 0xff );
    CS_gyro_stop;
    CS_gyro_start;
        SPI_sendByte( 0x2A | 0x80 );
        *y |= (SPI_sendByte( 0xff ) << 8);
    CS_gyro_stop;

    CS_gyro_start;
        SPI_sendByte( 0x2D | 0x80 );
        *z = SPI_sendByte( 0xff );
    CS_gyro_stop;
    CS_gyro_start;
        SPI_sendByte( 0x2C | 0x80 );
        *z |= (SPI_sendByte( 0xff ) << 8);
    CS_gyro_stop;
}

int main( void ){
    SysTick_Config( SystemCoreClock / 1000 );
    initialize();

    SPI_writeData(0x20, 0xff);  //power on, settings from TM-library & datasheet
    SPI_writeData(0x21, 0x00);  //high-pass filter settings
    SPI_writeData(0x24, 0x10);  //high-pass filter en
    SPI_writeData(0x23, 0x20);  //scale 2000

    uint16_t x, y, z;
    while( 1 ){
        GetGyroValues( &x, &y, &z );
        printf( "x: %d\r\n", x );

        DelayMS( 100 );

    }
}


uint32_t sEE_TIMEOUT_UserCallback(void)
{
  /* TODO, implement your code here */
  while (1)
  {
  }
}//   This is required by Atollic

以下是显示x轴变化的示例图。（发现板或多或少在45度，当它在0度时 - 放下，然后输出稳定65000）

Answer 1

来自L3GD20 app note：

请注意最后一部分 “表示为二位补码” ;您错误地将数据解释为 unsigned 。看起来价值徘徊在零附近;或者实际上看起来你在一个位置上相当不稳定地握着它，但肯定不会以稳定的速度连续旋转它。该设备是陀螺仪而不是加速度计。它测量角速度而不是加速度（或倾斜 - 即由重力引起的加速度）。在静止时，您会在所有轴上看到零。您的图表显示的可能是您手抖动试图将其保持在45度。

void GetGyroValues( int16_t *x, int16_t *y, int16_t *z )

应该更成功，当然：

    int16_t x, y, z;

您可以通过积分角速度而非绝对角度来获得角度变化的近似测量值。即便如此，您可能需要经常校准零 - 集成中的小的非零偏差将表现为错误的慢速旋转。

Answer 2

从数据表L3GD20，表17中，OUT_XL位于地址0x28，OUT_XH位于地址0x29。所以你必须左移地址0x29而不是0x28的值，反之亦然。这也是Y和Z值。

void GetGyroValues( int16_t *x, int16_t *y, int16_t *z ){
    CS_gyro_start;
    SPI_sendByte( 0x28 | 0x80 );
    *x = SPI_sendByte( 0xff );
    CS_gyro_stop;
    CS_gyro_start;
    SPI_sendByte( 0x29 | 0x80 );
    *x |= (SPI_sendByte( 0xff ) << 8);
    CS_gyro_stop;

    CS_gyro_start;
    SPI_sendByte( 0x2A | 0x80 );
    *y = SPI_sendByte( 0xff );
    CS_gyro_stop;
    CS_gyro_start;
    SPI_sendByte( 0x2B | 0x80 );
    *y |= (SPI_sendByte( 0xff ) << 8);
    CS_gyro_stop;

    CS_gyro_start;
    SPI_sendByte( 0x2C | 0x80 );
    *z = SPI_sendByte( 0xff );
    CS_gyro_stop;
    CS_gyro_start;
    SPI_sendByte( 0x2D | 0x80 );
    *z |= (SPI_sendByte( 0xff ) << 8);
    CS_gyro_stop;
}

STM32F429-DISC1上的陀螺仪表现异常

2 个答案: