ADXL345 SPI总线需要帮助AtMega644

Question

您好我正在尝试使AtMega644上的SPI总线与ADXL345加速计进行通信。我总是得到0回来，我不是我要去错的地方。任何帮助表示赞赏。我使用的是avr-gcc而不是Arduino的代码库。谢谢

#define F_CPU 18000000 
#define BAUDRATE 115200 
#define UBRRVAL (F_CPU/(BAUDRATE*16UL)) -1 
#define SPI_CS  PB0 
#define DDR_SPI  DDRB 
#define DD_MOSI  PB5 
#define DD_MIOS  PB6 
#define DD_SCK  PB7 

#include <avr/io.h> 
#include <util/delay.h> 
#include <avr/interrupt.h> 

#include "serial.h" 

/** 
* 
*/ 
void clear_spics(){ 
    PORTB |= _BV(SPI_CS); // high 
    delay_ms(30); 
} 

/** 
* 
*/ 
void set_spics(){ 
    PORTB &=~ _BV(SPI_CS); // low 
    delay_ms(30); 
} 

/** 
* 
*/ 
void InitSPI(){ 
    // make the MOSI, SCK, and SS pins outputs 
    DDRB |= (1 << DD_MOSI) | (1 << DD_SCK) | (1 << SPI_CS); 

    // make sure the MISO pin is input 
    DDRB &= ~(1 << DD_MIOS); 

    /* Enable SPI, Master, set clock rate fck/128 */ 
    SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0)|(1<<SPR1); 
} 

/** 
* 
*/ 
unsigned char WriteByteSPI(unsigned char cReg, unsigned char cData){ 
    set_spics(); 
    /* Start transmission send register */ 
    SPDR = cReg; 
    /* Wait for transmission complete */ 
    while(!(SPSR & (1<<SPIF))) 
     { /* NOOP */ } 

    clear_spics(); 
    set_spics(); 
    SPDR = cData; 
    /* Wait for transmission complete */ 
    while(!(SPSR & (1<<SPIF))) 
     { /* NOOP */ } 

    clear_spics(); 
    return SPDR; 
} 


int main(){ 
    char data; 
    USART_Init(); 
    InitSPI(); 
    //tell axdl345 use 4 wire spi communication 
    WriteByteSPI(0x31,0x00); 



    for(;;){ 
     data = WriteByteSPI(0x36,0); 
     send_byte(data); 
     delay_ms(2000); 
    } 

    //never get here 
    return 0; 
} 

Answer 1

这是我所需要的。我需要用0x80掩码设置读取位。

/** 
* This writes to a register with the data passed to the address passed 
* @param unsigned char cReg - the address of the register you wish to write to 
* @param unsigned char cData - the data you wish to write to the register 
*/ 
unsigned char WriteByteSPI(unsigned char cReg, unsigned char cData){ 
    set_spics(); 
    /* Start transmission send register */ 
    SPDR = cReg; 
    /* Wait for transmission complete */ 
    while(!(SPSR & (1<<SPIF))) 
     { /* NOOP */ } 
    SPDR = cData; 
    /* Wait for transmission complete */ 
    while(!(SPSR & (1<<SPIF))) 
     { /* NOOP */ } 
    clear_spics(); 
    return SPDR; 
    } 

/** 
* This adds the read bit to the address and passes it to the Write command 
* @param cReg - unsigned char the register you wish to read 
*/ 
unsigned char ReadByteSPI(unsigned char cReg){ 
    return WriteByteSPI((cReg | ADXL345_SPI_READ),0xAA); 
}