//Define Constants---------------------------------------------------
#define USB_PORT /dev/ttyACM3
#define PAGESIZE 64

//Include Header Files-----------------------------------------------
#include<stdlib.h>
#include<stdio.h>
#include<time.h>
#include<errno.h>
#include<unistd.h>
#include<termios.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<sys/resource.h>

//Prototypes---------------------------------------------------------
void delay(int delay_time);
void print_attrTermios(struct termios * ptr_attr);

//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//Main-Program
int main(int argc, const char * argv[]){

//initializing USART at USB_PORT-------------------------------------
	int USB = open("/dev/ttyACM3", O_RDWR|O_NOCTTY);
	if(isatty(USB)==0){
		printf("ERROR: No File Descriptor! \n");
		return 0;
	}
	struct termios * ptr_attr = (struct termios *)
									malloc(sizeof(struct termios));
	if(ptr_attr==NULL){
		printf("ERROR: Termios not available \n");
		return 0;
	}
	tcgetattr(USB, ptr_attr);
	(*ptr_attr).c_iflag = IGNPAR;
	(*ptr_attr).c_oflag = 0;
	(*ptr_attr).c_cflag = CS8|CREAD;
	(*ptr_attr).c_lflag = 0;
	cfsetspeed(ptr_attr, B19200);
	tcsetattr(USB, TCSANOW ,ptr_attr);
	delay(1000);

//Establishing  Connection-------------------------------------------
	char req[] = "REQ";
	char ack[] = "ACK";
	char * ptr_ack = &ack[0];
	char * ptr_input = (char *)malloc(3*sizeof(char));
		char * ptr_req = &req[0];
		while(1){
			write(USB, ptr_req, 3*sizeof(char));
//			tcflush(USB, TCIFLUSH);
			read(USB, ptr_input, 3*sizeof(char));
//			tcflush(USB, TCOFLUSH);
			printf("%s \n", &ptr_input[0]);
		}
		//delay(100);
	close(USB);
	return EXIT_SUCCESS;
}	
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++


//Delay-Function-----------------------------------------------------
void delay(int delay_time){
	clock_t time1 = clock();
	while(((clock()-time1)/CLOCKS_PER_SEC)*1000
			 							!= (clock_t)delay_time);
}

//Print Termios-Attributes-------------------------------------------
void print_attrTermios(struct termios * ptr_attr){
	printf("Input Mode Flag: %d \n", (*ptr_attr).c_iflag);
	printf("Output Mode Flag: %d \n", (*ptr_attr).c_oflag);
	printf("Control Mode Flag: %d \n", (*ptr_attr).c_cflag);
	printf("Local Mode Flag: %d \n", (*ptr_attr).c_lflag);
	printf("Baudrate Input: %d \n", (*ptr_attr).c_ispeed);
	printf("Baudrate Output: %d \n", (*ptr_attr).c_ospeed);
}