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
}
}