eeprom.c

ADS1241与MSP430F449接口设计

#include "hpa449lib.h"
#include "eeprom.h"

/*
******************************************************************************
** [function]
** EEPromWrite
** [puropse]
** writes data to a Microchip 24LC256 EEPROM
** [parameters]
** EEPromAddress - lower address bit of the EEPROM
** StartAddress - Startaddress where to read from
** Length - Number of bytes to write
** Buffer - Start address of the buffer that contains the data
** [returns]
** success
*/
int EEPromWrite(int EEPromAddress, unsigned int StartAddress, 
   unsigned int Length, char * Buffer)
{
   int i, fOK;
   
   I2C_Start();
   // send command byte
   fOK = I2C_SendByte(MCP24LC256_FIXED_ADDRESS | (EEPromAddress & 0x0f));

   // eventually, we need to brake up transfers, if they span multiple pages
   while (Length > 0 && fOK)
   {
      // determine how many bytes we have to a page boundary
      int nThisBytes = 64 -StartAddress % 64;
      if (nThisBytes > Length)
         nThisBytes = Length;  
	   // now nThisBytes contains the number of bytes within one page
      
      // send address byte high byte
      if (fOK)
      {
         fOK = I2C_SendByte((StartAddress >> 8) & 0xff);
      }
      // send address low byte
      if (fOK)
      {
         fOK = I2C_SendByte((StartAddress) & 0xff);
      }
      
      for (i=0; i< nThisBytes && fOK; i++)
      {
         fOK &= I2C_SendByte(*Buffer++);
	   }
	   
      // do the stop condition this will trigger the write process
      I2C_Stop();
      
      // adjust Length and Startaddress
      Length -= nThisBytes;
      StartAddress += nThisBytes;
      
      // wait for the write to complete
      i = 1000;   // limit the number of tries
      do
      {
         I2C_Start();
         // send command byte
         fOK = I2C_SendByte(MCP24LC256_FIXED_ADDRESS | (EEPromAddress & 0x0f));
	   } while (!fOK && (i-- > 0));
   }
   
   // end with a stop condition to put the bus into an idle state
   I2C_Stop();
   
   return fOK;
}

/*
******************************************************************************
** [function]
** EEPromRead
** [puropse]
** reads from an Microchip 24LC256 EEPROM
** [parameters]
** Site - Site on the HPA449
** EEPromAddress - lower address bit of the EEPROM
** StartAddress - Startaddress where to read from
** Length - Number of bytes to read
** Buffer - Start address of the buffer that receives the data, must be
**   at least <Length> bytes long
** [returns]
** success
*/
int EEPromRead(int EEPromAddress, unsigned int StartAddress, 
   unsigned int Length, char * Buffer)
{
   int i, fOK;
      
   I2C_Start();
   // send command byte
   fOK = I2C_SendByte(MCP24LC256_FIXED_ADDRESS | (EEPromAddress & 0x0f));
   // send address byte high byte
   if (fOK)
   {
      fOK = I2C_SendByte((StartAddress >> 8) & 0xff);
   }
   // send address low byte
   if (fOK)
   {
      fOK = I2C_SendByte((StartAddress) & 0xff);
   }
   // repeated start condition
   if (fOK)
   {
      I2C_Start();
      fOK = I2C_SendByte(MCP24LC256_FIXED_ADDRESS | (EEPromAddress & 0x0f) | 0x01);
   }
   if (fOK)
   {
      for (i=0; i< Length; i++)
      {
         // receive the bytes NACK when the last byte was received
         *Buffer++ = I2C_ReceiveByte(i != Length-1);
	   }
   }
   // do the stop condition
   I2C_Stop();
   return fOK;
}