//External reference to transmit ring buffer
extern unsigned char t_buffer[];	// transmit ring buffer 
extern unsigned char t_start;  	// ring start
extern unsigned char t_end;      // ring end
extern unsigned char interfaceStyle; // Human readable or Machine readable

#define RXenable UCSRB.7
#define TXenable UCSRB.5

//******************* Communication ***********************          

// Add a single character to the transmit buffer
void AddTx(char c){
  unsigned char newt_end;       
  
  // if the buffer is full, block operation
  newt_end = (t_end+1)%RINGSIZE;
  while(newt_end == t_start) {}
  
  // add data and update counter
  t_buffer[t_end] = c;
  t_end = newt_end;
  TXenable=1; 
}

// Adds a string to the transmit buffer
void WriteSerString(char *ws)
{
  // wsp will be destroyed during addition to the transmit buffer
  char *wsp;

  strcpy(wsp,ws);
 
  // add wsp to buffer by element
  while(*wsp) AddTx(*wsp++);
 
}

// Adds a numerical byte as hex to the transmit buffer
void WriteSerHex(char character)
{
  char c;
  c = character>>4;
  if (c>9)
    c = c + '0' + 7;
  else
    c = c + '0';
  AddTx(c);
  
  c = (character << 4) >> 4;
  if (c>9)
    c = c + '0' + 7;
  else
    c = c + '0';
  AddTx(c);
}

// Adds a number to the transmit buffer
void WriteSerNumber(long num)
{
  unsigned long posnum;
  char number[16];
  int j = 16;
  number[--j] = '\0';
  if (num < 0) {
    posnum = (unsigned long) -(num+1);
    posnum++;
  }
  else {
    posnum = (unsigned long) num;
  }

  number[--j] =  ('0' + (char)(posnum % 10));
  posnum /= 10;
  while(posnum != 0) {
    number[--j] =  ('0' + (char) (posnum % 10));
    posnum /= 10;
  }
  if (num < 0)
    number[--j] = '-';
  WriteSerString(&number[j]); 
}

// Adds a number to the transmit buffer
void WriteSerInt(int num)
{
  unsigned int posnum;
  char number[16];
  int j = 16;
  number[--j] = '\0';
  if (num < 0) {
    posnum = (unsigned long) -(num+1);
    posnum++;
  }
  else {
    posnum = (unsigned long) num;
  }

  number[--j] =  ('0' + (char)(posnum % 10));
  posnum /= 10;
  while(posnum != 0) {
    number[--j] =  ('0' + (char) (posnum % 10));
    posnum /= 10;
  }
  if (num < 0)
    number[--j] = '-';
  WriteSerString(&number[j]); 
}

// Adds a data packet to the transmit buffer
void WriteSerPacket(int time, char* datapacket){
  unsigned char i;


  if(interfacestyle == 'h'){
    AddTx('8');
    AddTx(' ');
    WriteSerInt(time);
    AddTx(' ');
    for (i=1; i<=5; i++) {
      WriteSerHex(datapacket[i]);
      AddTx(' ');
    }
    AddTx('\r');
    AddTx('\n');
  }
  else if (interfacestyle == 'm') {
    AddTx(8);
    AddTx((time>>8));
    AddTx((time<<8)>>8);
    AddTx(datapacket[1]);
    AddTx(datapacket[2]);
    AddTx(datapacket[3]);
    AddTx(datapacket[4]);
    AddTx(datapacket[5]);
  }
}