CMPS10 模块读取数值全为0XFF

#define SDA  PTBDD_PTBDD1
#define SCL  PTBDD_PTBDD0
#define SDA_IN       PTBD_PTBD1
#define SCL_IN       PTBD_PTBD0
void nop(void)    //d= 5 ,Delay  10us   
{
 byte d = 0;
 d = 5;
 while(d--)__RESET_WATCHDOG();
}
void display_compass(void)
{
  level = 0;
  read_i2c_buffer(0xC0,2,2);// read 2 bytes from compas starting at register 2, these are high byte and low byte for bearing. Put in buffer[0] and buffer[1]
 //buffer[0] = 0x01;
  //buffer[1] = 0x32;
 
  level = buffer[0]<<8;
  level += buffer[1];
 //level = ((buffer[0]<<8)+buffer[1]);  // Calculate bearing
  //level = 906;
  
  DispData_level[0] = level /1000 + '0';
  DispData_level[1] = level /100%10 + '0';
  DispData_level[2] = level /10%10 + '0';
  DispData_level[4] = level %10 + '0';
  DispData_level[5] = '\0';
  __RESET_WATCHDOG();
  LCD_P6x8Str(40,0,DispData_level); 
}

void read_i2c_buffer(byte addr, byte reg, byte byte_count)
{
  byte x = 0;
  //byte state = 0;
 i2c_start();     // send i2c data bytes 
  
  if(i2c_tx(addr&0xfe))// abort if slave does not acknowledge
   {  
     i2c_stop();
    for(x = 0; x < (byte_count); x++)
      {
       // buffer[x] = 255;  //no acknowledge,reset buffers
      }
    return;
   } 
  if(i2c_tx(reg)) // reg
   {    
     i2c_stop();
    for(x = 0; x < (byte_count); x++) 
      {
       // buffer[x] = 255;  //no acknowledge,reset buffers
      }
    return;
   }
 i2c_start();     // repeated start
    
 if(i2c_tx(addr|0x01)) // addr again including read bit
   {  
    i2c_stop();
    for(x = 0; x < (byte_count); x++) 
      {
       // buffer[x] = 255;  //no acknowledge,reset buffers
      }
    return;
   }
 for(x = 0; x< (byte_count-1); x++)
   {
     buffer[x] = i2c_rx(ACK);
   }
 buffer[byte_count-1] = i2c_rx(NACK); 
 i2c_stop();
}
byte i2c_rx(byte ack)
{
  byte x = 0;
  byte d = 0;
 SDA = 0;
 //nop();  /////
 for(x = 0; x < 8; x++) 
   {
    d <<= 1;  
    do 
      { 
       SCL = 0;
      }
    while(SCL_IN == 0);    // wait for any SCL clock stretching   
    nop();
    if(SDA_IN)
      {
        d |= 1;
      }
    SCL = 1;
    } 
  //nop();  /////
 if(ack) 
   {
     SDA = 1;
   }
 else 
   {
     SDA = 0;
   }
 SCL = 0;
 nop();       // send (N)ACK bit
 SCL = 1;
 SDA = 0;
 return d;
}

byte i2c_tx(byte d)
{
  byte x = 0;
 for(x=0; x<8; x++) 
   {
    nop();
    if(d&0x80 == 0x80)
      {
        SDA = 0;
      }
    else 
      {
        SDA = 1; 
      }
    nop();
    SCL = 0;
    nop();
     d <<= 1;
    SCL = 1;
   }
 //nop();
 SDA = 0;
 x = SDA_IN;
//nop(); ////
 SCL = 0;
 nop();
 
 SCL = 1;
 return x;  
}

void i2c_start(void)
{
 SDA = 0;      // i2c start bit sequence
 nop();
 SCL = 0;
 nop();
 SDA = 1;
 nop();
 SCL = 1;
 nop();
}

void i2c_stop(void)
{
 SDA = 1;      // i2c stop bit sequence
 nop();
 SCL = 0;
 nop();
 SDA = 0;
 nop();
}
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/****************************************************************
*                  Arduino CMPS10 example code                  *
*                    CMPS10 running I2C mode                    *
*                    by James Henderson, 2012                   *
*****************************************************************/
#include <Wire.h>
#include <SoftwareSerial.h>

#define ADDRESS 0x60                                          // Defines address of CMPS10

#define LCD_RX              0x02                              // RX and TX pins used for LCD0303 serial port
#define LCD_TX              0x03
#define LCD03_HIDE_CUR      0x04
#define LCD03_CLEAR         0x0C
#define LCD03_SET_CUR       0x02

SoftwareSerial lcd03 =  SoftwareSerial(LCD_RX, LCD_TX);      // Defines software serial port for LCD03

void setup(){
  Wire.begin();                                               // Conects I2C
  lcd03.begin(9600);
  lcd03.write(LCD03_HIDE_CUR);
  lcd03.write(LCD03_CLEAR);
}

void loop(){
   byte highByte, lowByte, fine;              // highByte and lowByte store high and low bytes of the bearing and fine stores decimal place of bearing
   char pitch, roll;                          // Stores pitch and roll values of CMPS10, chars are used because they support signed value
   int bearing;                               // Stores full bearing
   
   Wire.beginTransmission(ADDRESS);           //starts communication with CMPS10
   Wire.write(2);                              //Sends the register we wish to start reading from
   Wire.endTransmission();

   Wire.requestFrom(ADDRESS, 4);              // Request 4 bytes from CMPS10
   while(Wire.available() < 4);               // Wait for bytes to become available
   highByte = Wire.read();           
   lowByte = Wire.read();            
   pitch = Wire.read();              
   roll = Wire.read();               
   
   bearing = ((highByte<<8)+lowByte)/10;      // Calculate full bearing
   fine = ((highByte<<8)+lowByte)%10;         // Calculate decimal place of bearing
   
   display_data(bearing, fine, pitch, roll);  // Display data to the LCD03
   
   delay(100);
}

void display_data(int b, int f, int p, int r){    // pitch and roll (p, r) are recieved as ints instead oif bytes so that they will display corectly as signed values.
  
  lcd03.write(LCD03_SET_CUR);                     // Set the LCD03 cursor position
  lcd03.write(1);  
  lcd03.print("CMPS10 Example V:");
  lcd03.print(soft_ver());                        // Display software version of the CMPS10
  
  delay(5);                                       // Delay to allow LCD03 to proscess data  
  
  lcd03.write(LCD03_SET_CUR);
  lcd03.write(21);  
  lcd03.print("Bearing = ");                      // Display the full bearing and fine bearing seperated by a decimal poin on the LCD03
  lcd03.print(b);                               
  lcd03.print(".");
  lcd03.print(f);
  lcd03.print("  ");

  delay(5);

  lcd03.write(LCD03_SET_CUR);                     // Display the Pitch value to the LCD03
  lcd03.write(41);
  lcd03.print("Pitch = ");
  lcd03.print(p);
  lcd03.print(" ");

  delay(5);
  
  lcd03.write(LCD03_SET_CUR);                     // Display the roll value to the LCD03
  lcd03.write(61);
  lcd03.print("Roll = ");
  lcd03.print(r);
  lcd03.print(" ");
}

int soft_ver(){
   int data;                                      // Software version of  CMPS10 is read into data and then returned
   
   Wire.beginTransmission(ADDRESS);
   // Values of 0 being sent with write need to be masked as a byte so they are not misinterpreted as NULL this is a bug in arduino 1.0
   Wire.write((byte)0);                           // Sends the register we wish to start reading from
   Wire.endTransmission();

   Wire.requestFrom(ADDRESS, 1);                  // Request byte from CMPS10
   while(Wire.available() < 1);
   data = Wire.read();           
   
   return(data);
}
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看下这个代码  arduino的


我的I2C调试经验是，首先用示波器查看你发出来的波形是否正确，然后将总线接到例如24LC01 EEPROM上来判断是否可以可靠操作。 最好做一个I2C库封装起来，方便使用。

在I2C通信库OK的前提下，然后第三步，再接你最新使用的I2C设备，根据提供的操作手册和实例代码发送相应的数据。