#define BUFSIZE 80
unsigned int Get_Idx;
unsigned int Put_Idx;
unsigned char Tx_Buf[BUFSIZE];

int putchar(int ch)
{
  unsigned int Get_Idx_Copy;
  unsigned int Put_Idx_Copy;
  Put_Idx_Copy = Put_Idx;
  __enter_critical();
  Get_Idx_Copy = Get_Idx;
  __exit_critical(); 
  Put_Idx_Copy += 1;
  if(Put_Idx_Copy >= BUFSIZE)Put_Idx_Copy = 0;
  if(Put_Idx_Copy == Get_Idx_Copy){
    return (-1);
  }
  if(ch == -1) return (-2); // buffer not full check 
  Tx_Buf[Put_Idx_Copy] = (unsigned char)ch;
  Put_Idx = Put_Idx_Copy;
  return (ch);
}