Serial Interface

The Lego EV3 uses a TTL RS232 serial interface to communicate with external sensors. The following program can be used to read from sensors such as the gyroscope, sonar and color sensors.

/*
 * Robot Navigation Program
 * www.robotnav.com
 *
 * (C) Copyright 2013 - 2014 Navigation Solutions, LLC
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <fcntl.h>
#include <stdio.h>
#include  <sys/mman.h>
#include "lms2012.h"

const char PORT = 0x0; //EV3 label minus 1
const int MAX_SAMPLES  = 100;
int main()
{
	//DEFINE VARIABLES
	int file;
	UART *pUart; //UART porte user level handler
	int i;
	
	//INITIALIZE DEVICE
	//Open the device uart device file
	if((file = open(UART_DEVICE_NAME, O_RDWR | O_SYNC)) == -1)
	{
		printf("Failed to open device\n");
		return -1; 
	}
	//Map kernel device to be used at the user space level
	pUart  =  (UART*)mmap(0, sizeof(UART), PROT_READ | PROT_WRITE, MAP_FILE | MAP_SHARED, file, 0);
	if (pUart == MAP_FAILED)
	{
		printf("Failed to map device\n");
		return -1;
	}
	
	//PROCESS SENSOR DATA
	printf("Device is ready\n");
	for(i = 0;i<MAX_SAMPLES;i++)
	{
		printf("UART Value: %d\n", (unsigned char)pUart->Raw[PORT][pUart->Actual[PORT]][0]);
		sleep(1);
	}

	//CLOSE DEVICE
	printf("Clossing device\n");
	close(file);
	return 0;
}