我对7146 iic读的理解,帮我看看对不对?

/* 读I2C */
/* add   :  器件地址
   subadd:  内部地址
   */
ULONG IICRead(BYTE add, BYTE subadd)
{
ULONG trans;
#define START 0x3
#define CONT  0x2
#define STOP  0x1
#define NOP   0x0
add|=0x00010000;   //read----add is 0x48 or 0x4a
trans = (add    << 24 ) |
       (subadd << 16 ) |
       ( START << 6  ) |
       ( CONT  << 4  ) |
       ( STOP  << 2  ) ;
   WriteReg(SAA7146_I2C_TRANSFER,trans);
   WriteReg(SAA7146_I2C_STATUS,0x500);
   WriteReg(SAA7146_MC2,(SAA7146_MC2_UPLD_I2C << 16 ) | 0xFFFF);
}

>add|=0x00010000; //read----add is 0x48 or 0x4a
^^^^^^^^^^^^^^^delete
>trans = (add << 24 ) |
changed to: trans = ((add|0x01) << 24) |
>(subadd << 16 ) |
ok and insert:
     (add << 8) |
>( START << 6 ) |
ok, it\'s start read
>( CONT << 4 ) |
ok
>( STOP << 2 ) ;
^^^^^^^^^^^^^(start<<2); //this means start write
>WriteReg(SAA7146_I2C_TRANSFER,trans);
ok
>WriteReg(SAA7146_I2C_STATUS,0x500);
ok
>WriteReg(SAA7146_MC2,(SAA7146_MC2_UPLD_I2C << 16 ) | >0xFFFF);
ok

[编辑 -  6/17/02 by  gung]

这样对吗？好像读还是不行！！！
/* 写I2C */
/* add   :  器件地址
   subadd:  内部地址
   value : 值
   */
void IICWrite(BYTE add, BYTE subadd,BYTE value)
{
ULONG trans;
#define START 0x3
#define CONT  0x2
#define STOP  0x1
#define NOP   0x0
trans = (add    << 24 ) |
   (subadd << 16 ) |
(value  << 8  ) |
( START << 6  ) |
( CONT  << 4  ) |
( STOP  << 2  ) ;
   WriteReg(SAA7146_I2C_TRANSFER,trans);
   WriteReg(SAA7146_I2C_STATUS,0x500);
   WriteReg(SAA7146_MC2,(SAA7146_MC2_UPLD_I2C << 16 ) | 0xFFFF);
}
/* 读I2C */
/* add   :  器件地址
   subadd:  内部地址
   */
BYTE IICRead(BYTE add, BYTE subadd)
{
ULONG trans;
#define START 0x3
#define CONT  0x2
#define STOP  0x1
#define NOP   0x0

trans = ((add|0x01) << 24 ) |
   (subadd << 16 ) |
(add << 8  ) |
( START << 6  ) |
( CONT  << 4  ) |
( STOP  << 2  ) ;
   WriteReg(SAA7146_I2C_TRANSFER,trans);
   WriteReg(SAA7146_I2C_STATUS,0x500);
   WriteReg(SAA7146_MC2,(SAA7146_MC2_UPLD_I2C << 16 ) | 0xFFFF);
//好像trans值没变！
   trans=trans>>8;
   trans^=0x000000ff;
   return trans;
}

1. 仔细看一下说明书，SAA7146_I2C_TRANSFER寄存器中三个字节发送顺序是反过来的。
2. 注意，读的过程应该是start write --> continue --> start read， 而不是start --> continue --> stop

既然是读，最后总要把寄存器的值读回来阿

wait i2c to be programed;

readreg(SAA7146_I2C_TRANSFER);

getdata;

既然是读，最后总要把寄存器的值读回来阿

wait i2c to be programed;

wait i2c operation done
readreg(SAA7146_I2C_TRANSFER);

getdata;

to:Guan
按你的意思,读应该这样:

2. 注意，读的过程应该是start write --> continue --> start read， 而不是start --> continue --> stop

trans = ((add|0x01) << 24 ) |
(subadd << 16 ) |
(add << 8 ) |
( START << 6 ) |
( CONT << 4 ) |
( START << 2 ) ;


可是这个该如何改呢?
 

1. 仔细看一下说明书，SAA7146_I2C_TRANSFER寄存器中三个字节发送顺序是反过来的。

trans = ((add|0x01) << 24 ) |
(subadd << 16 ) |
(add << 8 ) |
( START << 6 ) |
( CONT << 4 ) |
( START << 2 ) ;

按照这个就对的
我说的反过来就是说：
trans = ((add|0x01) << 24 ) | //第三个字节
(subadd << 16 ) | //第二个字节
(add << 8 ) | //第一个字节
( START << 6 ) | //第三个字节为start read
( CONT << 4 ) | //第二个字节为continue
( START << 2 ) ; //第一个字节为start write

如果按照你原先的程序：
trans = ((add|0x01) << 24 ) |
(subadd << 16 ) |
(add << 8 ) |
( START << 6 ) |
( CONT << 4 ) |
( STOP << 2 ) ; //第一个字节
第一个字节就stop了当然没有数据拉。

另外，ppl说得对，还要等待i2c完成再取数据。

即检测i2c_status的bit0是否为0。

那读到的数据在那里呢？

很对不起，我记错了，我重新看了一下以前的代码，应该是这样的：
WriteReg(I2C_STATUS, 0X500);
WriteReg(MC2, 0x00010001);
WriteReg(I2C_STATUS, 0X500);
WriteReg(MC2, 0x00010001);//clear errors, usually twice

trans = ((add) << 24 ) | //first
(subadd << 16 ) | //second
(add|0x01 << 8 ) | //third
( START << 6 ) | //start write
( CONT << 4 ) | //continue
( START << 2 ) ; //start read
WriteReg(I2C_TRANSFER, trans);
WriteReg(I2C_STATUS, 0x500);
WriteReg(MC2, 0x00010001);


While(ReadReg(I2C_STATUS) | 0x00000001); // waiting for unbusy
if(ReadReg(I2C_STATUS) | 0x00000002) t << \"I2C Error\" << EOL;

WriteReg(I2C_TRANSFER, 0x00000080); //continue to receive byte

WriteReg(I2C_STATUS, 0x500);
WriteReg(MC2, 0x00010001); //upload

while(ReadReg(I2C_STATUS)| 0x00000001);
if(ReadReg(I2C_STATUS) | 0x00000002) t << \"I2C Error\" << EOL;

ByteReturned = (ReadReg(I2C_TRANSFER) & 0xff000000)>>24;




[编辑 -  6/18/02 by  gung]

gung:留个qq吧！我的：76138572
没有的话我送你一个！

2408481

gung:
大哥，为何qq不理我啊?

While(ReadReg(I2C_STATUS) | 0x00000001);
这里 |应该换成&吧