MMA7455加速度传感器測量角度

使用加速度传感器应该注意几点：

第一：确保你的IIC是正确的；

第二，首先必须校准系统,校准方法，例如以下：将7455平放，保证z轴向下，这是假设系统是Ok的，那么x轴输出为0，y轴输出为0，z轴输出为63左右，假设不为以上參数，应该做例如以下调整：測量值比实际值小的情况下，往校准寄存器里面写入一个2*误差值；假设測量值假设大于实际值，应该写入一个值为相应误差的负值的ASCII码，比方假设測出值为70，那么应该写入-16，即（0xf0）；

下面就是我调试mma7455的代码：

#include "msp430f5438.h"
#include "public.h"
#include "simulate_iic.h"
#include <stdbool.h>

#include "init.h"

#include "mma7455.h"
#include "lcd1602.h"
#include<math.h>
typedef unsigned int uint;
typedef unsigned char uchar;
char mma7455write_byte(unsigned char reg,unsigned char data)//寄存器地址，数据
{
  char flag;
 // WDTCTL = WDTPW + WDTHOLD; // 禁止看门狗定时器
  iic_start();//起始信号
  write_byte(0x3a);//数据发送
  flag=get_ack();//接受应答位，即数据成功发送后，接受到的应答
  if(flag)
  {
    flag=0;
    write_byte(reg);//数据发送
  }

  flag=get_ack();//接受应答位，即数据成功发送后，接受到的应答
  if(flag)
  {
    flag=0;
    write_byte(data);
  }

  flag=get_ack();
  if(flag)
  {
    flag=0;
    iic_stop();
    return 0;
  }

  return 1;

}

 char readMMA7455Byte(unsigned char regadd)
{
  char flag;
  char z;
  z=0;
  iic_start();
  write_byte(0x3a);//先写入器件地址
  flag=get_ack();
  if(flag)
  {
    write_byte(regadd);//有应答之后再写寄存器地址
    flag=0;
  }

  flag=get_ack();
  if(flag)
  {
    flag=0;
    iic_start();//继续等应答之后写入该地址和读命令，但是认为这不必要这么做
    write_byte(0x3b);//但是时间的原因，仅仅有找着实例的操作先写着，以后再改动
  }

  flag=get_ack();
  if(flag)
  {
    flag=0;
    z=read_byte();
  }

  send_ack();

  iic_stop();

  return z;

}
// X:255 1.65V -1.00g
// 012345678901234567
void Cvt_Str(char zifu[], char V1)
{
  char characters[17]="0123456789ABCDEF";
   char tv=0;

  tv=V1/100;
  zifu[2] = characters[tv];
  tv=(V1%100)/10;
  zifu[3] = characters[tv];
  tv=V1%10;
  zifu[4] = characters[tv];

  zifu[5] = ‘ ‘;

  zifu[6] = ‘0‘;
  zifu[7] = ‘x‘;
  tv=V1/16;
  zifu[8] = characters[tv];
  tv=V1%16;
  zifu[9] = characters[tv];

  zifu[10] = ‘ ‘;

  if(V1>127)
  {
    zifu[11] = ‘-‘;
    tv=255-V1;
    zifu[12] = characters[tv/63];
    zifu[13] = ‘.‘;
    zifu[14] = characters[((tv*100/63)%100)/10];
    zifu[15] = characters[(tv*100/63)%10];
  }
  else
  {
    zifu[11] = ‘+‘;
    tv=V1;
    zifu[12] = characters[tv/63];
    zifu[13] = ‘.‘;
    zifu[14] = characters[((tv*100/63)%100)/10];
    zifu[15] = characters[(tv*100/63)%10];
  }
  zifu[16] = ‘g‘;
}
uint	arc_tan2(uchar Ax,uchar Ay)
{
	int	diat_t;
	float		m;
	m=atan2(Ay,Ax);
	diat_t=(int)(m*1800/3.14);
	return	diat_t;
}
uint measure()
{
	uchar x;
	uchar y;
	uint x1,y1;
	uchar	xsign,ysign;
	uint angle;
	angle=0;
		x=readMMA7455Byte(0x06);
		y=readMMA7455Byte(0x07);
		x=x+0x2C;
		y=y+0x25;
		if(x>127)
		{
			x=255-x;
			x1=((float)x*100)/63.0;
			xsign=0x2b;
		}
		else
		{
			x1=((float)x*100)/63.0;
			xsign=0x2d;
		}
		if(y>127)
		{
			y=255-y;
			y1=((float)y*100)/63.0;
			ysign=0x2b;
		}
		else
		{
			y1=((float)y*100)/63.0;
			ysign=0x2d;
		}
	angle = arc_tan2(x1,y1);
	/*if(xsign==0x2b&&ysign==0x2b)
	{
		angle = arc_tan2(x1,y1);
	}
	else	if(xsign==0x2b&&ysign==0x2d)
	{
		angle = 900+arc_tan2(y1,x1);;
	}
	else	if(xsign==0x2d&&ysign==0x2d)
	{
		angle = 2700-angle;
	}
	else	if(xsign==0x2d&&ysign==0x2b)
	{
		angle = 2700+angle;
	}*/
	return angle;
}
void main()
{
	  char txtbuf[16]="X:255 -1.00g";
	  //uchar x,y,x2,y2;
	  //volatile uint x1,y1;
	 // uchar j,k;
	  clk_init();
	  lcd1602_pin_init();
	  lcd_init();
	  delay_ms(50);
	  while(mma7455write_byte(0x16,0x005));
	  while(mma7455write_byte(0x10,0xff));//校正X值
	  while(mma7455write_byte(0x11,0x07));
	  while(mma7455write_byte(0x12,0x18));//校正Y值
	  while(mma7455write_byte(0x14,0xDC));//校正Z值
	  while(mma7455write_byte(0x15,0xFF));
	  while(1)
	  {
		/*lcd_pos(0,0);
		  lcd_wdat(‘a‘);
		  lcd_wdat(‘n‘);
		  lcd_wdat(‘g‘);
		  lcd_wdat(‘l‘);
		  lcd_wdat(‘e‘);
		  lcd_wdat(‘:‘);

		  lcd_printf(measure());//x
		  //delay_ms(1000);
		  //lcd_wcmd(0x01);	*/		//显示清屏

			/*x=readMMA7455Byte(0x06);
			y=readMMA7455Byte(0x07);
			x2=x+0x2C;
			y2=y+0x25;
			x=x+0x2C;
			y=y+0x25;
			if(x>0x7f)
			{
				x=255-x;
				j=1;
				x1=((float)x*100)/63.0;
			}
			else
			{
				x1=((float)x*100)/63.0;
				j=0;
			}
			if(y>0x7f)
			{
				y=255-y;
				y1=((float)y*100)/63.0;
				k=1;
			}
			else
			{
				y1=((float)y*100)/63.0;
				k=0;
			}
			lcd_pos(0,0);
			if(j==1) lcd_wdat(‘-‘);
			else lcd_wdat(‘+‘);
			lcd_char(x1);
			lcd_pos(0,1);
			if(k==1) lcd_wdat(‘-‘);
			else lcd_wdat(‘+‘);
			lcd_char(y1);
			delay_ms(1000);
			lcd_wcmd(0x01);

			  lcd_pos(0,0);
			  Cvt_Str(txtbuf,x2);
			  txtbuf[0]=‘X‘;
			  lcd_string(txtbuf);
			  lcd_pos(0,1);
			  Cvt_Str(txtbuf,y2);
			  txtbuf[0]=‘Y‘;
			  lcd_string(txtbuf);
			  delay_ms(1000);
			  lcd_wcmd(0x01);*/			//显示清屏
			  lcd_pos(0,0);
			  Cvt_Str(txtbuf,readMMA7455Byte(0x08));
			  txtbuf[0]=‘Z‘;
			  lcd_string(txtbuf);
			  lcd_pos(0,1);
			  lcd_printf(arc_tan2(readMMA7455Byte(0x08),readMMA7455Byte(0x06)));
			  delay_ms(1000);
			  lcd_wcmd(0x01);			//显示清屏

			  lcd_pos(0,1);
			  Cvt_Str(txtbuf,readMMA7455Byte(0x06));
			  txtbuf[0]=‘X‘;
			  lcd_string(txtbuf);
			  lcd_pos(0,0);
			  Cvt_Str(txtbuf,readMMA7455Byte(0x07));
			  txtbuf[0]=‘Y‘;
			  lcd_string(txtbuf);
			  delay_ms(1000);
			  lcd_wcmd(0x01);			//显示清屏
	  }
}