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Maxim > 设计资料库 > 应用笔记 > 1-Wire®器件
关键词: i2c, 1-wire, 桥, ds2482, 线驱动器, 指南, 摆率, 波形, 主机
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   APP 3684: Jul 07, 2006
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应用笔记3684

如何使用带有I²C接口的DS2482 1-Wire®主控制器

摘要：DS2482是I²C到1-Wire网络协议的桥接器件。桥接器DS2482可以使任何具备I²C通信功能的主机产生正确定时和具有摆率控制的1-Wire波形。本应用笔记是DS2482 I²C至1-Wire线驱动器的用户指南，详细介绍了通用1-Wire主控制器操作的通信过程。

1. 引言

1-Wire通信协议可利用DS2482产生，DS2482是I²C至1-Wire网络的桥接器件。该桥接器件可使带有I²C接口的主机产生正确定时的1-Wire波形。图1所示为DS2482配置的简化框图。执行该协议并浏览所有DS2482指令相当费时并容易混淆。为此，本应用笔记介绍了采用DS2482有效实现基本的与扩展的1-Wire操作的方法。详细介绍了处理1-Wire通信的I²C输入数据包结构。这些操作为执行当前和未来1-Wire器件的所有功能打下了全面的基础。以这种方式概要介绍1-Wire操作，使1-Wire应用可独立于1-Wire主机类型。

本文仅作为DS2482数据资料的补充，并不能替代数据资料。DS2482可提供两种配置，单通道1-Wire主控制器(DS2482-100)和8通道1-Wire主控制器(DS2482-800)。

图1. 与1-Wire网络进行I2C通信的DS2482桥接器功能简图。
图1. 与1-Wire网络进行I²C通信的DS2482桥接器功能简图。

2. 1-Wire接口

下面给出几个基本的1-Wire函数，称之为原函数，也就是为了执行所有1-Wire操作，应用中必须具备的函数。第一个函数是使总线上所有1-Wire从器件复位，使其为接收来自1-Wire主控制器的指令做好准备。第二个函数完成1-Wire主控制器向从器件写入一位的操作，而第三个函数完成从1-Wire从器件中读取一位的操作。由于必须由1-Wire主控制器启动所有的1-Wire位通信，所以“读取”实际上是在“写入”一位后采样得到的结果。几乎所有其他1-Wire操作都可以由这三个操作构成。例如，向1-Wire总线写1个字节相当于8次写一位操作。

1-Wire搜索算法也可以利用这三个原始函数构成。通过1-Wire的triplet命令，DS2482可以执行搜索功能，这大大降低了搜索操作所需的通信量。

表1所示是三个基本原函数(OWReset，OWWriteBit/OWReadBit和OWWriteByte/OWReadByte)以及其他三个非常有用的函数(OWBlock，OWSearch和msDelay)，它们构成了一系列主要的基本1-Wire操作。这些操作名称将在下文中使用。

表1. 基本的1-Wire操作
Operation Description
OWReset Sends the 1-Wire reset stimulus and check for pulses of 1-Wire slave devices.
OWWriteBit/OWReadBit Sends or receives a single bit of data to the 1-Wire bus.
OWWriteByte/OWReadByte Sends or receives a single byte of data to the 1-Wire bus.
OWBlock Sends and receives multiple bytes of data to and from the 1-Wire bus.
OWSearch Performs the 1-Wire Search Algorithm (see Application Note 187 mentioned above).
msDelay Delays at least the specified number of milliseconds.

扩展的1-Wire函数(如高速通信函数)并没有包括在上表的基本操作中。一些1-Wire从器件可以工作在两种不同的通信速率下：标准速率和高速模式。所有器件都支持标准速率模式。高速速率大约是标准速率的10倍。DS2482同时支持这两种1-Wire速率。

1-Wire器件通常从1-Wire总线上获取部分或全部工作电源。不过有些器件在 协议的特定位置需要额外供电。例如，某个器件可能需要进行温度转换或计算SHA-1散列。这种操作的电源是通过使能1-Wire总线的强上拉来提供的。在该供电期间，不能进行正常通信。DS2482通过设置强上拉标志(SPU)位来供电，这将在1-Wire的下一个字节/位通信完成后启动强上拉。DS2482-100具有一个外部引脚(PCTLZ)，可控制大电流强上拉。

表2列出了用于1-Wire速率设定、供电和编程脉冲的扩展1-Wire操作。

表2. 扩展的1-Wire操作
Operation Description
OWSpeed Sets the 1-Wire communication speed, either standard or overdrive. Note that this only changes the communication speed of the 1-Wire master; the 1-Wire slave device must be instructed to make the switch when going from normal to overdrive. The 1-Wire slave will always revert to standard speed when it encounters a standard-speed 1-Wire reset.
OWLevel Sets the 1-Wire power level (normal or power delivery).
OWReadBitPower Reads a single bit of data from the 1-Wire bus and optionally applies power delivery immediately after the bit is complete.
OWWriteBytePower Sends a single byte of data to the 1-Wire bus and applies power delivery immediately after the byte is complete.

3. 主机配置

DS2482的主机应具有一个I²C通信端口。本文并没有讲述主机的配置。然而，主机必须提供标准I²C接口操作。所需的操作请参阅表3。

表3. 所需的I²C主机操作
Operation Description
InitI2C Sets the I²C communication speed and selects the DS2482 device. The I2C_clock_delay is the time between clock pulses for I²C communication. The DS2482_slave_address is the I²C address for the DS2482.
I2CBus_write Writes an I²C byte to the selected DS2482. The byte is passed to the function to write.
I2CBus_write_packet Writes a packet of I²C bytes to the selected DS2482. The buffer of bytes along with the length of the buffer is passed to the function.
I2CBus_read Reads an I²C byte from the DS2482. The byte that was read is returned.

3.1. 配置DS2482

在尝试1-Wire操作之前，主机必须设置I²C至1-Wire线驱动器DS2482，并与其同步。要与DS2482通信，主机必须知道其从地址。图2所示为DS2482-100和DS2482-800的从地址。

图2. DS2482的I2C从地址
图2. DS2482的I²C从地址

3.2. DS2482的I²C命令

下列符号说明来自于DS2482数据资料，以简写符号表示，用来说明器件的I²C通信过程。接下来，我们会重复这些通信过程，并为实现基本和扩展1-Wire操作提供附加注释和C语言代码实例。

I²C通信过程—符号说明
SYMBOL DESCRIPTION
S START Condition
AD, 0 Select DS2482 for Write Access
AD, 1 Select DS2482 for Read Access
Sr Repeated START Condition
P STOP Condition
A Acknowledged
A\ Not acknowledged
(Idle) Bus not busy
<byte> Transfer of one byte
DRST Command 'Device Reset', F0h
WCFG Command 'Write Configuration', D2h
SRP Command 'Set Read Pointer', E1h
1WRS Command '1-Wire Reset', B4h
1WWB Command '1-Wire Write Byte', A5h
1WRB Command '1-Wire Read Byte', 96h
1WSB Command '1-Wire Single Bit', 87h
1WT Command '1-Wire Triplet', 78h

3.3. 数据方向表示法

Master-to-Slave Slave-to-Master

本文中许多图中的数据方向表示方法指出了通信方向是主机到从机(灰色)，还是从机到主机(白色)。可通过每个符号的底色来确定通信方向。

4. 器件复位

图3是实现器件复位的I²C通信实例。复位实例1给出了DS2482复位命令，可实现器件状态机逻辑的完全复位，并终止所有正在进行的1-Wire通信。器件的复位命令代码是0xF0。

图3. 上电后进行器件复位。该实例包括可选的读访问，以检验命令是否成功执行。
图3. 上电后进行器件复位。该实例包括可选的读访问，以检验命令是否成功执行。 
// initialize the I2C port
if(!InitI2C(I2C_clock_delay,DS2482_slave_address))
{
   // Report an error that occurred
}

// reset the DS2482
// DRST is 0xF0
if(!I2CBus_write(DRST))
{
   // Report an error that occurred
}
实例1. 复位器件代码

5. DS2482的1-Wire操作

以下是向DS2482发送的命令，可影响1-Wire通信。

5.1. OWReset

Reset命令(0xB4)在1-Wire总线上执行1-Wire复位/在线应答检测。通过状态寄存器中的在线应答脉冲检测(PPD)和短路检测(SD)域，可以采样和报告1-Wire总线的状态。图4所示为1-Wire复位命令的I²C通信过程。实例2为发送的命令，将检查状态寄存器以确定在线应答脉冲状态。

图4. 1-Wire复位。开始或终止1-Wire通信。轮询1-Wire的忙状态，直到1-Wire命令完成为止，等到1-Wire空闲(1WB = 0)时，然后读取结果。
图4. 1-Wire复位。开始或终止1-Wire通信。轮询1-Wire的忙状态，直到1-Wire命令完成为止，等到1-Wire空闲(1WB = 0)时，然后读取结果。 
// OWReset
//
// Resets the 1-Wire using I2C through the DS2482.
//
// returns Success or Failure
//
uchar OWReset()
{
   uchar buffer;
   uchar test;
 
   // reset the 1-Wire line
   // resetOneWireCommand is 0xB4
   if(!I2CBus_write(resetOneWireCommand))
   {
      // Report an error that occurred
   }

   for(;;)// checking if 1-Wire busy
   {
      // checking LSB of status register
      // to see if 1-Wire is busy.
      test = I2CBus_read()| 0xFE;
      if(test == 0xFE)
      {break;}
   }

   // checking for presence pulse detect
   test = I2CBus_read() | 0xFC;
   if(test == 0xFE)
   {
      return Success;   // Presence Pulse found
   }
   else
   {
      return Failure;   // No presence pulse
   }
}
实例2. OWReset代码

5.2. OWWriteBit/OWReadBit

1-Wire位命令(0x87)生成一个1-Wire位时隙。图5所示是1-Wire位命令的I²C通信代码。图6是包含该位位置的字节。其中，如果V是1b，则生成写1时隙，如果V是0b，则生成写0时隙。实例3为OWWriteBit代码，实例4为OWReadBit代码。

图5. 1-Wire位命令。在1-Wire总线上生成一个时隙，当1WB从1变为0时，状态寄存器保持1-Wire位命令的有效结果。
图5. 1-Wire位命令。在1-Wire总线上生成一个时隙，当1WB从1变为0时，状态寄存器保持1-Wire位命令的有效结果。

图6. 1-Wire位命令。在1-Wire总线上产生单个时隙。
图6. 1-Wire位命令。在1-Wire总线上产生单个时隙。 
// OWWriteBit - Writes a single bit to 1-Wire using the DS2482.
//
// value - bit to be written to the 1-Wire (0 or 1)
//
// Return Success or Failure
//
uchar OWWriteBit(uchar value)
{
   uchar buff[3];
   uchar test;

   buff[0] = onewireBitCommand;   // 1-Wire bit command
   
   if(value)
   {
      buff[1] = 0xFF;
   }
   else
   {
      buff[1] = 0x7F;
   }

   if(!I2CBus_write(&buff[0],2))
   {
      return FAILURE;
   }

   // checking if 1-Wire busy
   // Check here to make sure the 1-Wire isn’t 
   // busy so other commands don’t have to check 
   // before proceeding.
   for(;;)
   {
      if(!I2CBus_read(&buff[0],1))
      {
         return FAILURE;
      }

      test = buff[0] | 0xFE;

	  if(test == 0xFE)
	  {
	     break;
	  }
   }

   return SUCCESS;
}
Example 3. OWWriteBit code. 
// OWReadBit
//
// Returns 0 or 1 for the bit read.
uchar OWReadBit()
{
   uchar buff[3];

   OWWriteBit(1);

   buff[0] = setReadPointerCommand;
   buff[1] = statusRegister;

   if(!I2CBus_write(&buff[0],2))
   {
      // Report an error that occurred
   }
   else if(!I2CBus_read(&buff[2],1))
   {
	// Report an error that occurred
   }

   if(buff[2] & 0x20)
   {
      return 1;	
   }
   else
   {
      return 0;
   }
}
实例4. OWReadBit代码

5.3. OWWriteByte

1-Wire写字节命令(0xA5)向1-Wire总线写入单个数据字节。在DS2482执行该命令之前，必须结束1-Wire的工作状态。图7所示为通过I²C写1-Wire字节的情况。代码实例5在发送写字节命令之前，先检查1-Wire是否忙。

图7. 1-Wire写字节。向1-Wire总线发送命令代码。当1WB从1变为0时，完成1-Wire写字节命令。
图7. 1-Wire写字节。向1-Wire总线发送命令代码。当1WB从1变为0时，完成1-Wire写字节命令。 
// OWWriteByte
//
// Writes a 1-Wire byte using I2C commands sent to the DS2482.
//
// wrByte - The byte to be written to the 1-Wire.
//
void OWWriteByte(uchar wrByte)
{
   uchar buffer[2];
   uchar test;
 
   // set the read pointer to the status 
   // register to check 1-Wire busy
   buffer[0] = setReadPointerCommand;  // 0xE1
   buffer[1] = statusRegister;         // 0xF0

   if(!I2CBus_write(buffer,2))
   {
      // Report an error that occurred
   }

   // checking if 1-Wire busy
   for(;;)
   {
      test = I2CBus_read() | 0xFE;

      if(test == 0xFE)
      {
	   break;
      }
   }

   buffer[0] = writeByteCommand;  // 0xA5
   buffer[1] = wrByte;  

   if(!I2CBus_write_packet(buffer,2))
   {
      // Report an error that occurred
   }

   // checking if 1-Wire busy
   for(;;)
   {
      test = I2CBus_read() | 0xFE;

      if(test == 0xFE)
      {
	   break;
      }
   }
}
实例5. OWWriteByte代码

5.4. OWReadByte

1-Wire读字节命令(0x96)从1-Wire总线读取单个数据字节。在DS2482执行该命令之前，必须等1-Wire的工作状态结束。图8所示为I²C通信情况。1-Wire读字节命令见代码实例6。在发送读字节命令之前，必须检查1-Wire的工作状态是否结束。

图8. 1-Wire读字节。从1-Wire总线上读取一个字节。轮询状态寄存器直到1WB位从1变为0。然后设置读指针指向读数据寄存器(代码E1h)，并再次访问该器件，读取从1-Wire总线上得到的数据字节。
图8. 1-Wire读字节。从1-Wire总线上读取一个字节。轮询状态寄存器直到1WB位从1变为0。然后设置读指针指向读数据寄存器(代码E1h)，并再次访问该器件，读取从1-Wire总线上得到的数据字节。 
// OWReadByte
// 
// Reads a 1-Wire byte using I2C commands to the DS2482.
//
// returns the byte read
//
uchar OWReadByte
{
   uchar buffer[2];
   uchar test;

   // set the read pointer to the status 
   // register to check 1-Wire busy
   buffer[0] = setReadPointerCommand;  // 0xE1
   buffer[1] = statusRegister;         // 0xF0

   if(!I2CBus_write_packet(buffer,2))
   {
      // Report an error that occurred
   }

   // checking if 1-Wire busy
   for(;;)
   {
      test = I2CBus_read() | 0xFE;

      if(test == 0xFE)
      {
	   break;
      }
   }

   // readByteCommand is 0x96
   if(!I2CBus_write(readByteCommand))
   {
      // Report an error that occurred
   }

   buffer[0] = setReadPointerCommand;  // 0xE1
   buffer[1] = readDataRegister;       // 0xE1

   if(!I2CBus_write_packet(buffer,2))
   {
      // Report an error that occurred
   }
   // gets the byte that was read
   else
   {
      buffer[2] = I2CBus_read();
   }

   return buffer[2];
}
实例6. OWReadByte代码

5.5. OWBlock

由于不通过字节命令就不能传输数据块，因此，OWBlock操作只是调用字节操作。实例7为OWBlock代码实例。 
// OWBlock – writes/reads a block of data
// block – block of data
// return – Success or failure of the operation.
uchar OWBlock (uchar *block, uchar len)
{
   uchar buffer[2];
   int i;

   for(i=0;i<len;i++)
   {
      owWriteByte(block[i]);

      buffer[0] = setReadPointerCommand;    // The read pointer value is 0xE1
      buffer[1] = readDataRegister;         // The read data register value is 0xE1

      if(!I2CBus_write(&buffer[0],2))
      {
         return FAILURE;
      }
      else
         block[i] = I2CBus_read();
   }

   return SUCCESS;
}
实例7. OWBlock代码

5.6 OWSearch/1-Wire Triplet命令

Triplet命令(0x78)可在1-Wire总线上产生3个时隙，其中包括两个读时隙和一个写时隙。方向字节(DIR)决定了写时隙的类型(图9)。实例8示出了仅挂接一个器件情况下使用搜索命令的1-Wire Triplet命令代码。有关1-Wire搜索算法的解释参见应用笔记187，该应用笔记给出了1-Wire Triplet命令的I²C设置。

图9. 1-Wire Triplet。在1-Wire总线上实现搜索ROM功能。完成该1-Wire功能需要一段空闲时间。然后在读取模式下访问器件，通过1-Wire Triplet命令得到结果。
图9. 1-Wire Triplet。在1-Wire总线上实现搜索ROM功能。完成该1-Wire功能需要一段空闲时间。然后在读取模式下访问器件，通过1-Wire Triplet命令得到结果。 
// Global value for the current serial number
uchar SearchSerialNum[8];

// oneWireSearch
//
// Does a 1-Wire search using the 1-Wire Triplet command.  
//
// resetSearch – Reset the search(1) or not(0).
// lastDevice  - If the last device has been found(1) or not(0).
// deviceAddress – The returned serial number.
//
// returns SUCCES or FAILURE
//
uchar OWSearch(uchar resetSearch, uchar *lastDevice, uchar *deviceAddress)
{
   uchar retVal = FAILURE;
   uchar bit_number = 1;
   uchar last_zero = 0;
   uchar serial_byte_number = 0;
   uchar serial_byte_mask = 1;
   uchar firstBit, secondBit, dir;
   uchar i = 0;

   if(resetSearch)
   {
      lastDevice = 0;
	 LastDiscrepancy = 0;
   }

   // if the last call was not the last one
   if (!(*lastDevice))
   {
      // reset the 1-wire
      // if there are no parts on 1-wire, return FALSE
      if(!OWReset())
      {
         // reset the search
         lastDevice = 0;
         LastDiscrepancy = 0;
         return FAILURE;
      }

      // Issue the Search ROM command
      OWWireByte(0xF0);

      // loop to do the search
      do
      {
         if (bit_number < LastDiscrepancy)
         {
            if(SearchSerialNum[serial_byte_number] & serial_byte_mask)
               dir = 1;
            else
               dir = 0;
         }
         else
         {
            // if equal to last pick 1, if not then pick 0
            if(bit_number==LastDiscrepancy)
               dir = 1;
            else
               dir = 0;
         }

         if(!owTriplet(&dir, &firstBit, &secondBit))
         {
            return FAILURE;
         }

         // if 0 was picked then record its position in LastZero
         if (firstBit==0 && secondBit==0 && dir == 0)
         {
            last_zero = bit_number;
	    }

         // check for no devices on 1-wire
         if (firstBit==1 && secondBit==1)
            break;

         // set or clear the bit in the SerialNum byte serial_byte_number
         // with mask serial_byte_mask
         if (dir == 1)
	       SearchSerialNum[serial_byte_number] |= serial_byte_mask;		
         else
            SearchSerialNum[serial_byte_number] &= ~serial_byte_mask;

         // increment the byte counter bit_number
         // and shift the mask serial_byte_mask
         bit_number++;
         serial_byte_mask <<= 1;

         // if the mask is 0 then go to new SerialNum[portnum] byte serial_byte_number
         // and reset mask
         if (serial_byte_mask == 0)
         {
            serial_byte_number++;
            serial_byte_mask = 1;
         }
      }
      while(serial_byte_number < 8);  // loop until through all SerialNum[portnum]    

      retVal = FAILURE;
      // if the search was successful then
      if (bit_number == 65)//|| crcl))
      {
         // search successful so set LastDiscrepancy,LastDevice
         LastDiscrepancy = last_zero;
         if(LastDiscrepancy==0)
            *lastDevice = SUCCESS;
         else
		*lastDevice = FAILURE;

         for(i=0; i<8; i++)
	    {
            deviceAddress[i] = SearchSerialNum[i];
	    }

         return SUCCESS;
      }
   }

   // if no device found then reset counters so next 'next' will be
   // like a first
   if (!retVal || !SearchSerialNum[0])
   {
      LastDiscrepancy = 0;
      *lastDevice = FAILURE;
      retVal = FAILURE;
   }

   return retVal;
}

// oneTriplet
//
// Uses the 1-Wire Triplet command.
//
// dir – Returns the direction that was chosen (1) or (0).
// firstBit  - Returns the first bit of the search (1) or (0).
// secondBit – Returns the complement of the first bit (1) or (0).
//
// returns SUCCES or FAILURE
//
uchar owTriplet(uchar *dir, uchar *firstBit, uchar *secondBit)
{
   uchar buff[3];
   uchar test;

   buff[0] = 0x78;

   if(*dir>0)
      *dir = (uchar)0xFF;

   buff[1] = *dir;

   if(!I2CBus_write(&buff[0],2))
   {
      lcd_putchar('f');
   }

   if(!I2CBus_read(&buff[2],1))
   {
      return FAILURE;
   }
   else
   {
      test = buff[2] & 0x20;
	 if(test == 0x20)
	    *firstBit = 1;
	 else
	    *firstBit = 0;

	 test = buff[2] & 0x40;
	 if(test == 0x40)
	    *secondBit = 1;
	 else
	    *secondBit = 0;

	 test = buff[2] & 0x80;
	 if(test == 0x80)
	    *dir = 1;
	 else
	    *dir = 0;

      return SUCCESS;
   }

   return FAILURE;
}
实例8. OWSearch代码

6. 扩展的1-Wire工作模式

6.1. OWSpeed

实例9给出了如何用DS2482改变1-Wire总线速率，提供高速或标准两种速率。 
// OWSpeed – changes the 1-Wire speed to normal or overdrive.
//           A Overdrive match rom or overdrive skip rom will be needed.
//
// speed – overdrive (Overdrive) or standard (Standard) speed.
// state_config – The current configuration byte settings.
//
// return – success or failure of the operation.
//
uchar OWSpeed(uchar speed, uchar state_config)
{
   uchar buffer[2];

   buffer[0] = writeConfigCommand;
   
   if(speed == Overdrive)
      buffer[1] = (state_config | 0x08) & 0x7F;
   else
      buffer[1] = (state_config | 0x80) & 0xF7;

   if(!I2CBus_write_packet(buffer,2))
   {
      return FAILURE;
   }

   return SUCCESS;
}
实例9. OWSpeed代码

6.2. OWLevel

实例10给出了如何用DS2482改变1-Wire总线的电平。提供正常和供电两种模式。 
// OWLevel
//
// level – Normal or Power Delivery mode
// state_config – The current configuration settings
//
// Returns if the operation was Successful or not.
//
uchar OWLevel(uchar level, uchar state_config)
{
   uchar buffer[2]; 

   buffer[0] = writeConfigCommand;

   // NORMAL = 0, POWER_DELIV = 1
   if(level == NORMAL) 
      buffer[1] = (state_config | 0x01) & 0xEF;
   else
      buffer[1] = (state_config | 0x10) & 0xFE;     

   if(!I2CBus_write_packet(buffer,2))
   {
      return FAILURE;
   }

   return SUCCESS;
}
实例10. OWLevel代码

6.3. OWReadBitPower

实例11是OWReadBitPower所使用的代码。OWReadBitPower读取一个1-Wire位并执行供电功能。当配置寄存器中的强上拉(SPU)位使能时，在下一位或字节通信完成后，DS2482将拉高1-Wire总线。 
// OWReadBitPower 
//
// config_byte – current configuration settings
// delay – ms delay used before disabling active pullup
//
// Returns the bit information read.
//
uchar OWReadBitPower(uchar config_byte)
{ 
   uchar buffer[2];
   uchar return_bit;
   
   buffer[0] = writeConfigCommand;
   buffer[1] = (config_byte | 0x04) & 0xBF;   
   // Sets strong pullup active so after the next byte or bit 
   // strong pullup will be active

   if(!I2CBus_write_packet(buffer,2))
   {
      Error;
   }

   return OWReadBit();  
}
实例11. OWReadBitPower代码

6.4. OWWriteBytePower

实例12为OWWriteBytePower所采用的代码，OWWriteBytePower写入1-Wire字节并执行供电功能。当配置寄存器中的强上拉(SPU)位使能时，在下一位或字节通信完成后，DS2482将拉高1-Wire总线。 
// OWWriteBytePower 
//
// config_byte – current configuration settings.
// wrbyte – byte to be written before the strong pullup is active
// delay – ms delay used before disabling active pullup
//
// Returns failure or success of the operation.
//
uchar OWWriteBytePower(uchar config_byte, uchar wrbyte)
{ 
   uchar buffer[2];
  
   buffer[0] = writeConfigCommand;
   buffer[1] = (config_byte | 0x04) & 0xBF;   
   // Sets strong pullup active so after the next byte or bit 
   // strong pullup will be active

   if(!I2CBus_write_packet(buffer,2))
   {
      return FAILURE;
   }

   OWWriteByte(wrbyte);

   return SUCCESS;
}
实例12. OWWriteBytePower代码

结束语

DS2482已经过测试，可成功完成I²C接口至1-Wire的转换。本文给出了基于I²C至1-Wire线驱动器DS2482的完整1-Wire接口方案。所提供的代码实例可以在任何一个具有I²C通信端口的主机系统中轻松实现。另外还提供完整的C语言执行代码，可以点击下载。

1-Wire是Maxim Integrated Products, Inc.的注册商标。

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更多信息  APP 3684: Jul 07, 2006
DS2482-100 单通道1-Wire主控制器 完整的数据资料
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DS2482-800 八通道1-Wire主控制器 完整的数据资料
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 AN3684, AN 3684, APP3684, Appnote3684, Appnote 3684



         


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