#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

int main (void)
{
	//Asking for the COM port to use and attempting to open it
	char COMPort[5] = {'C','O','M','?','\0'};
	HANDLE hSerial;
	
	printf("What COM port do you want to use ?\n");
	scanf("%c",&COMPort[3]);
	
	hSerial = CreateFile(COMPort,
	GENERIC_READ | GENERIC_WRITE,
	0,
	0,
	OPEN_EXISTING,
	FILE_ATTRIBUTE_NORMAL,
	0);
	
	if(hSerial==INVALID_HANDLE_VALUE)
	{
		if(GetLastError()==ERROR_FILE_NOT_FOUND)
		{
			printf("Serial port does not exist\n");//serial port does not exist. Inform user.
			system("pause");
			return -1;
		}
			printf("An error occured while trying to open the serial port\n");//some other error occurred. Inform user.
			system("pause");
			return -1;
	}
	
	//Setting communication parameters
	DCB dcbSerialParams = {0};
	
	dcbSerialParams.DCBlength=sizeof(dcbSerialParams);
	
	if (!GetCommState(hSerial, &dcbSerialParams)) 
	{
		printf("An error occured while trying to control the COM port\n");//error getting state
		system("pause");
		return -1;
	}
	
	dcbSerialParams.BaudRate=CBR_115200;
	dcbSerialParams.ByteSize=8;
	dcbSerialParams.StopBits=ONESTOPBIT;
	dcbSerialParams.Parity=NOPARITY;
	
	if(!SetCommState(hSerial, &dcbSerialParams))
	{
		printf("An error occured while trying to apply communication settings\n");//error setting serial port state
		system("pause");
		return -1;	
	}
	
	//Setting tiemouts for reading and writing processes
	COMMTIMEOUTS timeouts={0};
	
	timeouts.ReadIntervalTimeout=50;
	timeouts.ReadTotalTimeoutConstant=50;
	timeouts.ReadTotalTimeoutMultiplier=10;
	timeouts.WriteTotalTimeoutConstant=50;
	timeouts.WriteTotalTimeoutMultiplier=10;
	
	if(!SetCommTimeouts(hSerial, &timeouts))
	{
		printf("An error occured while trying to apply timeout settings\n");//error occureed. Inform user
		system("pause");
		return -1;	
	}
	
	//Writing data to the COM port
	char c = 'a';
	DWORD bytesWritten = 0;
	int again = 0;
	
	do
	{
		if(!WriteFile(hSerial, &c, sizeof(c), &bytesWritten, NULL))
		{
			printf("An error uccured while trying to write data to the COM port\n");//error occurred. Report to user.
			system("pause");
			return -1;	
		}
		else
		{
			printf("Successful writing of %ld bytes\n",bytesWritten);
		}
		
		printf("Send another char ? Type 1, 0 otherwise\n");
		scanf("%d",&again);
	}
	while(again == 1);
	
	
	//Closing the COM port we've just used
	CloseHandle(hSerial);
	
	system("pause");
	return 0;
}