/* 
 * maxqi2c.c v0.1
 *
 * Author: Paul Holden
 *
 */
 
#include "maxqi2c.h"
#include <intrinsics.h>

// At 20MHz, a NOP requires 50nS
#define NOP __no_operation()

// I2C Timing Info for 400KHz and 100KHz
#ifdef  I2C_400_KHZ
  #define I2C_WAIT_SU_STA  /* 600nS*/_i2c_wait_600ns()
  #define I2C_WAIT_HD_STA  /* 600nS*/_i2c_wait_600ns()
  #define I2C_WAIT_T_LOW   /*1300ns*/_i2c_wait_1300ns()
  #define I2C_WAIT_HD_DAT  /* 300nS*/NOP;NOP;NOP;NOP;NOP;NOP
  #define I2C_WAIT_SU_DAT  /* 100nS*/NOP;NOP
  #define I2C_WAIT_SU_STO  /* 600nS*/_i2c_wait_600ns()
  #define I2C_WAIT_T_HIGH  /* 600nS*/_i2c_wait_600ns()
  void _i2c_wait_600ns()   {NOP;NOP;NOP;NOP;}
  void _i2c_wait_1300ns()  {NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;NOP;}
#else
  #define I2C_WAIT_SU_STA  /*4700nS*/_i2c_wait_4700ns()
  #define I2C_WAIT_HD_STA  /*4000nS*/_i2c_wait_4000ns()
  #define I2C_WAIT_T_LOW   /*4700ns*/_i2c_wait_4700ns()
  #define I2C_WAIT_HD_DAT  /*5000nS*/_i2c_wait_5000ns()
  #define I2C_WAIT_SU_DAT  /* 250nS*/NOP;NOP;NOP;NOP;NOP
  #define I2C_WAIT_SU_STO  /*4000nS*/_i2c_wait_4000ns()
  #define I2C_WAIT_T_HIGH  /*4000nS*/_i2c_wait_4000ns()
  void _i2c_wait_4000ns()  {volatile unsigned int i=0x04; do{i--;}while(i);}
  void _i2c_wait_4700ns()  {volatile unsigned int i=0x05; do{i--;}while(i);}
  void _i2c_wait_5000ns()  {volatile unsigned int i=0x05; do{i--;}while(i);}
#endif

/* Variables used for I2C driver */
__no_init volatile unsigned char *i2cData;     // Pointer to I2C data
__no_init volatile unsigned int   i2cDataLen;  // I2C data length (not incl addr)
__no_init volatile unsigned char  i2cDataAddr; // I2C address
__no_init volatile unsigned char  i2cDataTerm; // I2C termination
__no_init volatile unsigned char  ack;         // acknowledge result

/* Prototypes for low-level I2C commands */
void          _i2c_low_level_send_start    ();
void          _i2c_low_level_send_addr     ();
void          _i2c_low_level_send_dir_read ();
void          _i2c_low_level_send_dir_write();
void          _i2c_low_level_send_byte     (unsigned char i2cByte);
unsigned char _i2c_low_level_recv_byte     ();
void          _i2c_low_level_recv_ack      ();
void          _i2c_low_level_send_ack      ();
void          _i2c_low_level_send_nack     ();
void          _i2c_low_level_send_rep_start();
void          _i2c_low_level_send_stop     ();

/*
 * i2cInit() - see maxqi2c.h for documentation...
 */
void i2cInit()
{
   SDA        = 0;
   SCL        = 0;
   SDA_PULLUP = 0;
   SCL_PULLUP = 0;
}

/*
 * i2cIsAddrPresent() - see maxqi2c.h for documentation...
 */
unsigned char i2cIsAddrPresent()
{
   _i2c_low_level_send_start();
   _i2c_low_level_send_addr();
   _i2c_low_level_send_dir_write();
   _i2c_low_level_recv_ack();
   _i2c_low_level_send_stop();                  
   return ack;
}

/*
 * i2cSend() - see maxqi2c.h for documentation...
 */
unsigned char i2cSend()
{
   __no_init unsigned int i;

   // 1. Send addr
   if (i2cDataAddr)
   {
      _i2c_low_level_send_start();  
      _i2c_low_level_send_addr();
      _i2c_low_level_send_dir_write();
      _i2c_low_level_recv_ack();
      if (!ack)
      {
         _i2c_low_level_send_stop();
         return I2C_XMIT_FAILED;
      }
   }
   
   // 2. Send data
   for(i=0x0000; i<i2cDataLen; i++)
   {
      _i2c_low_level_send_byte(i2cData[i]);
      _i2c_low_level_recv_ack();
      if (!ack)
      {
         _i2c_low_level_send_stop();
         return I2C_XMIT_FAILED;
      }
   }
   
   // 3. Send termination
   if (i2cDataTerm == I2C_TERM_STOP)
      _i2c_low_level_send_stop();
   
   // 4. Return successful I2C transmit indicator
   return I2C_XMIT_OK;
}

/*
 * i2cRecv() - see maxqi2c.h for documentation...
 */
unsigned char i2cRecv()
{
   __no_init unsigned int i;

   // 1. Send addr
   if (i2cDataAddr)
   {
      _i2c_low_level_send_start();  
      _i2c_low_level_send_addr();
      _i2c_low_level_send_dir_read();
      _i2c_low_level_recv_ack();
      if (!ack)
      {
         _i2c_low_level_send_stop();
         return I2C_XMIT_FAILED;
      }
   }
   
   #ifdef I2C_CLOCK_STRETCHING
      SCL = 0;
      while (SCL_IN == 0);
   #endif
   
   // 2. Send data
   if (i2cDataLen)
      i2cData[0x0000] = _i2c_low_level_recv_byte();
      
   for(i=0x0001; i<i2cDataLen; i++)
   {
      _i2c_low_level_send_ack();
      i2cData[i] = _i2c_low_level_recv_byte();
   }
   
   // 3. Send termination
   if (i2cDataTerm == I2C_TERM_ACK)
   {
      _i2c_low_level_send_ack();
   }
   else if (i2cDataTerm == I2C_TERM_NACK_AND_STOP)
   {
      _i2c_low_level_send_nack();
      _i2c_low_level_send_stop();
   }
   
   // 4. Return successful I2C transmit indicator
   return I2C_XMIT_OK;
}

/*
 * _i2c_low_level_send_start() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_send_start()
{
   SDA = 1;
   I2C_WAIT_HD_STA;
   SCL = 1;
}

/*
 * _i2c_low_level_send_start() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_send_addr()
{
   volatile unsigned char mask = 0x80;
   do
   {
      I2C_WAIT_HD_DAT;
      SDA = ((i2cDataAddr&mask)==0);
      I2C_WAIT_SU_DAT;
      SCL = 0;
      I2C_WAIT_T_HIGH;
      SCL = 1;
      mask>>=1;
   } while (mask!=0x0001);
}

/*
 * _i2c_low_level_send_dir_read() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_send_dir_read()
{
   I2C_WAIT_HD_DAT;
   SDA = 0;
   I2C_WAIT_SU_DAT;
   SCL = 0;
   I2C_WAIT_T_HIGH;
   SCL = 1;
   I2C_WAIT_T_LOW;                            
}

/*
 * _i2c_low_level_send_dir_write() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_send_dir_write()
{
   I2C_WAIT_HD_DAT;
   SDA = 1;
   I2C_WAIT_SU_DAT;
   SCL = 0;
   I2C_WAIT_T_HIGH;
   SCL = 1;
   SDA = 0;
   I2C_WAIT_T_LOW;
}

/*
 * _i2c_low_level_send_byte() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_send_byte(unsigned char i2cByte)
{
   unsigned char mask = 0x80;
   do
   {
      I2C_WAIT_HD_DAT;
      SDA = ((i2cByte&mask)==0);
      I2C_WAIT_SU_DAT;
      SCL = 0;
      I2C_WAIT_T_HIGH;
      SCL = 1;
      mask>>=1;
   } while (mask!=0x0000);
}

/*
 * _i2c_low_level_recv_byte() - LOW-LEVEL FUNCTION
 */
unsigned char _i2c_low_level_recv_byte()
{
   unsigned char mask = 0x80;
   
   ack = 0x00;
   do
   {
      I2C_WAIT_HD_DAT;
      I2C_WAIT_SU_DAT;
      SCL = 0;
      I2C_WAIT_T_HIGH;
      ack += (SDA_IN)?mask:0;
      SCL = 1;
      mask>>=1;
   } while (mask!=0x0000);
   
   return ack;
}

/*
 * _i2c_low_level_recv_ack() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_recv_ack()
{
   SDA = 0;
   SCL = 0;
   I2C_WAIT_T_HIGH;
   ack = (SDA_IN==0);
   SCL = 1;
}

/*
 * _i2c_low_level_send_ack() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_send_ack()
{
   SDA = 1;
   SCL = 0;
   I2C_WAIT_T_HIGH;
   SCL = 1;
   SDA = 0;
}

/*
 * _i2c_low_level_send_nack() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_send_nack()
{
   SDA = 0;
   SCL = 0;
   I2C_WAIT_T_HIGH;
   SCL = 1;
}

/*
 * _i2c_low_level_send_rep_start() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_send_rep_start()
{
   I2C_WAIT_SU_STA;
   SDA = 1;
   I2C_WAIT_HD_STA;
   SCL = 1;
}

/*
 * _i2c_low_level_send_stop() - LOW-LEVEL FUNCTION
 */
void _i2c_low_level_send_stop()
{
   SDA = 1;
   I2C_WAIT_T_LOW;
   SCL = 0;
   I2C_WAIT_SU_STO;
   SDA = 0;
}