/* Name       : Chat Program via a serial port						     */
 /* Written By : ND         */

#include <string.h>
#include <stdlib.h>
#include <dos.h>
#include <stdio.h>
#include <conio.h>

#define COM1 0x3F8

#define THR 0
#define RBR 0
#define IER 1
#define FCR 2
#define LCR 3
#define MCR 4
#define LSR 5
#define MSR 6

#define DLL 0
#define DLM 1
#define DTR 0
#define RTS 1
#define CTS 4 //inside MSR
#define DSR 5

#define DLAB 7
// LSR Register: Error types and bits offsets
// Note: When the LSR is read, it is reset.
#define DR 0 //indicates that a byte is ready to be read from RBR
#define OVERRUN_ERROR 1
#define PARITY_ERROR 2
#define FRAMING_ERROR 3
#define BREAK_INTERRUPT 4
#define NUM_OF_ERRORS 4
#define THRE 5 //1 indicates I can write to the THR
#define TSRE 6

#define ON 1
#define OFF 0

#define ODD 1
#define EVEN 2
#define NUM_OF_PARITY_OPTIONS 3

#define ONE 0
#define TWO 1

#define UART_CLOCK_MAX_FREQUENCY 1843200
#define MULTIPLIER 16
#define MAX_SPEED_IN_BPS 115200

#define DEFAULT_SPEED_IN_BPS 2400
#define DEFAULT_WORD_LENGTH 8
#define DEFAULT_PARITY_VALUE 0
#define DEFAULT_STOP_BIT_LENGTH 1
#define DEFAULT_INTERRUPT_MODE 0

#define MINIMAL_WORD_LENGTH 5
#define MAXIMAL_WORD_LENGTH 8
#define MINIMAL_STOP_BIT_LENGTH 1
#define MAXIMAL_STOP_BIT_LENGTH 2

#define NUM_OF_SPEEDS 14
#define NUM_OF_BUFFER_ELEMENTS 13
#define SPEED_INDEX 0
#define WORD_LENGTH_INDEX 1
#define PARITY_INDEX 2
#define STOP_BIT_INDEX 3
#define NO_CHAR 256
#define ESC 27
#define ENTER 13


char glbBuffer[]={"hello out there"};
// This function changes the UART's settings.
// If BitNumber<0 the function sets on or off the whole register given
// to the function.
void SetABitOrAByteOnOrOff(int port, int OnOrOff, int RegisterOffset, int BitNumber)
{
	int shifter;

	if(BitNumber>=0)
	{
		shifter=1;
		shifter=shifter<<BitNumber;
	}
	else
	{
	  shifter=0;
	  shifter=~shifter;
	}

	if(OnOrOff==ON)
	{
		outp(port+RegisterOffset,inp(port+RegisterOffset) | shifter);
	}
	else     //off
	{
	 shifter=~shifter;
	 outp(port+RegisterOffset,inp(port+RegisterOffset) & shifter);
	}
}

// This function gets a setting from the UART.
// If the 'port' parameter is set to -1 then the function
// gets the information (or Byte) it needs to operate from the number
// that is set into the parameter 'RegisterOffset'.
int GetABitOrAByte(int port, int RegisterOffset,int BitNumber)
{
	int output;

	if(port!=-1)
	{
	output=inp(port+RegisterOffset);
	}
	else
	{
	  output=RegisterOffset;
	}

	if(BitNumber>=0)
	{
		output=output>>BitNumber;
		BitNumber=1;
		output=output&BitNumber;
	}

	return(output);
}

int GetABaudRate(int SpeedInBPS)
{
	long clock=UART_CLOCK_MAX_FREQUENCY;
	int multi=MULTIPLIER;
	unsigned int temp=0;

	temp=SpeedInBPS*multi;

	return(clock/temp);
}
// Inits the DLL and DLM registers with a new speed
void SetABaudRate(int port, int BaudRate)
{
	int lsb,msb;

	if(BaudRate<1)
	{
		BaudRate=GetABaudRate(DEFAULT_SPEED_IN_BPS);
	}

	lsb=BaudRate%0xFF;
	msb=BaudRate/0xFF;

	SetABitOrAByteOnOrOff(port,ON,LCR,DLAB);
	outp(DLL,lsb);
	outp(DLM,msb);
	SetABitOrAByteOnOrOff(port,OFF,LCR,DLAB);
}
int ReadABaudRate(int port)
{
	int lsb,msb;
	SetABitOrAByteOnOrOff(port,ON,LCR,DLAB);

	lsb=inp(DLL);
	msb=inp(DLM);

	SetABitOrAByteOnOrOff(port,OFF,LCR,DLAB);
msb=msb<<8;
return (lsb+msb);

}


void SetWordLength(int port, int NewLength)
{
	int first=OFF,second=OFF;

	switch (NewLength)
	{
		case 6:
			first=OFF;
			second=ON;
			break;
		case 7:
			first=ON;
			second=OFF;
			break;
		case 8:
			first=ON;
			second=ON;
			break;
		default:
			first=ON;
			second=ON;
	}

	SetABitOrAByteOnOrOff(port,first,LCR,0);
	SetABitOrAByteOnOrOff(port,second,LCR,1);
}

void SetParity(int port, int NewType)
{
	int parity=OFF;
	int type=OFF;

	if(NewType!=OFF)
	{
		if(NewType==ODD)
		{
			parity=ON;
			type=ODD-1;
		}
		else
		{
			parity=ON;
			type=EVEN-1;
		}
	}

	SetABitOrAByteOnOrOff(port,parity,LCR,3);
	SetABitOrAByteOnOrOff(port,type,LCR,4);
}

void SetStopBitLength(int port, int NewLength)
{
	if(NewLength==TWO)
	{
		SetABitOrAByteOnOrOff(port,ON,LCR,2);
	}
	else
	{
		SetABitOrAByteOnOrOff(port,OFF,LCR,2);
	}
}

void ChangeCommunicationSettings(int port, int SpeedInBPS, int WordLength,
								int parity, int StopBitLength, int InterruptMode)
{
	if(InterruptMode==OFF)
	{
		SetABitOrAByteOnOrOff(port,OFF,IER,-1);   /* Turn off interrupts */
	}

	SetABaudRate(port,GetABaudRate(SpeedInBPS));
	SetWordLength(port,WordLength);
	SetParity(port,parity);
	SetStopBitLength(port,StopBitLength);
}

void StartOrStopTheControlSystem(int port, int OnOrOff)
{
	if(OnOrOff==ON)
	{
		SetABitOrAByteOnOrOff(port,ON,MCR,RTS);
	}
	else
	{
		SetABitOrAByteOnOrOff(port,OFF,MCR,RTS);
	}
}

void KillTheConnection(int port)
{
	StartOrStopTheControlSystem(port,OFF);
	SetABitOrAByteOnOrOff(port,OFF,MCR,DTR); // Kill the connection
}

void SendAChar(int port, int aChar)
{
	outp(port+THR,aChar);
}

int GetAChar(int port)
{
	int aChar=NO_CHAR;

		aChar=inp(port+RBR);
	return(aChar);
}



void SendDataBufferToPort(int port, int index_of_buffer)
{
		SendAChar(port,glbBuffer[index_of_buffer]);
		printf("sent one char \n");
}

void SaveInfoToBuffer(int port)
{
	int i=0;

//	while(i<NUM_OF_BUFFER_ELEMENTS)
	{
		glbBuffer[i]=GetAChar(port);
		i++;
	}
}



char* GetAnErrorName(int BitNumber)
{
	char* output;

	switch(BitNumber)
	{
		case OVERRUN_ERROR:
			return("Overrun Error");
		case PARITY_ERROR:
			return("Parity Error");
		case FRAMING_ERROR:
			return("Framing Error");
		case BREAK_INTERRUPT:
			return("Break Interrupt");
		default:
			return("Bad Input");
	}
}

char* GetLastErrors(int port)
{
	int lsr,i=1,bit;
	char* output="\0";

	lsr=GetABitOrAByte(port,LSR,-1); // The LSR is reset after that command

	while(i<=NUM_OF_ERRORS)
	{
		bit=GetABitOrAByte(-1,lsr,i);

		if(bit==ON)
		{
			strcat(output,GetAnErrorName(i));
			strcat(output," | ");
		}
		i++;
	}

	return(output);
}

void StartToRECV(int port)
{
	int input=NO_CHAR;
	char byteRead;
	char* errors;
	int i=0;
	do
	{
		{

						if(GetABitOrAByte(port,LSR,DR)==ON)
						{
						printf("DR is indicating a byte has arrived\n");

						byteRead=GetAChar(port);
						printf("The byte we read is %c\n",byteRead);
						}
						else
						{
						printf("DR is indicating no byte arrived\n");
						}
		}
		i++;

		printf("\nplease type any char, ESC to exit\n");
		input=getch();
	}   while (input != ESC && i != 6); //only send 5 letters


}


void StartToChat(int port)
{
	int input=NO_CHAR;
	int output=NO_CHAR;
	char* errors;
	int i=0;

	do
	{
		{
						if(GetABitOrAByte(port,LSR,THRE)==ON)
						{
						printf("THRE is indicating it is ready for a byte");

						SendDataBufferToPort(port, i);
						}
						else
						{
						printf("THRE is indicating not ready for a byte");
						}
		}
		i++;

		printf("\nplease type any char, ESC to exit\n");
		input=getch();
	}   while (input != ESC && i != 6); //only send 5 letters


}


void main(int argc, char** argv)
{
	int baudrate;
	int port=COM1;
	int input=NO_CHAR;
	int dsr=OFF;
	char* title="COM Chat v1.0 ";
	char* porttext="\0";
	char mes[]={"(hit any key to continue)\n"};
	int fcr,msr;

  clrscr();

  printf("%s %s\n",title,mes);
  printf("Tell me the speed in BPS\n");
  scanf("%d",&baudrate);
  printf ("You typed %d. That requires a baud rate of %d \n ",baudrate, GetABaudRate(baudrate));
 SetABaudRate(port,GetABaudRate(baudrate));
 printf("The baud rate has been set to %d.  %s",ReadABaudRate(port), mes);
 getch();
 printf("MCR = %d\n",GetABitOrAByte(port,MCR,-1));
 printf("%s",mes);
 getch();

  msr = GetABitOrAByte(port,MSR,-1);
 printf("MSR = %d\n",msr);
 printf("%s",mes);
 getch();


SetABitOrAByteOnOrOff(port,OFF,MSR,-1);

  msr = GetABitOrAByte(port,MSR,-1);
 printf("Now MSR = %d\n",msr);
 printf("%s",mes);
 getch();

 SetABitOrAByteOnOrOff(port,OFF,MCR,DTR);
  printf("DTR = %d\n",GetABitOrAByte(port,MCR,DTR));
SetABitOrAByteOnOrOff(port,ON,MCR,DTR);
 printf("Now the DTR = %d\n %s",GetABitOrAByte(port,MCR,DTR),mes);
 getch();
 SetABitOrAByteOnOrOff(port,OFF,MCR,-1); // Reset the MCR
	SetABitOrAByteOnOrOff(port,OFF,LCR,-1); // Reset the LCR
									 //allow fifo on rbr

SetABitOrAByteOnOrOff(port,ON,FCR,0);
SetABitOrAByteOnOrOff(port,ON,FCR,1);
SetABitOrAByteOnOrOff(port,ON,FCR,2);


	ChangeCommunicationSettings(port,DEFAULT_SPEED_IN_BPS,
								DEFAULT_WORD_LENGTH
								,DEFAULT_PARITY_VALUE,
								DEFAULT_STOP_BIT_LENGTH,
								DEFAULT_INTERRUPT_MODE);

	 printf("Press, 1 to send, 2 to receive, or press esc to quit");

			input=getch();
		if (input =='1')
		{
						 printf("\nYou are sending.\n");
				StartToChat(port);
		}
		if (input == '2')
		{

						 printf("\nYou are receiving.\n");
				StartToRECV(port);
		}
	printf("\nLast Message\n %s",mes);
 getch();

}