#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <termios.h>
#include <time.h>

#define DS2480B_CMDMODE 0xE3
#define DS2480B_DATAMODE 0xE1

#define CHIPERROR -1
#define BUSERROR -2

int fd;

void ow_init(char *device) {
	struct termios attr;

	fd = open(device, O_RDWR | O_NOCTTY);
	if (fd < 0) {
		perror(device);
		exit(-1);
	}
	
	tcgetattr(fd, &attr);
	attr.c_cflag |= CLOCAL | CS8 | B9600;
	tcflush(fd, TCIFLUSH);
	tcsetattr(fd, TCSANOW, &attr);
}

void rs_writebyte(unsigned char byte) {
	if (write(fd, &byte, 1) != 1) {
		perror("rs_writebyte");
	}
	
	usleep(10000);
}

void rs_flush() {
	tcflush(fd, TCIFLUSH);
}

unsigned char rs_readbyte() {
	unsigned char result = 0x00;
	int timeout = time(NULL) + 5;
	int count;
	
	while (time(NULL) < timeout) {
		count = read(fd, &result, 1);
		
		if (count < 0 && count != EAGAIN) {
			perror("rs_readbyte");
			exit(CHIPERROR);
		}
		
		if (count == 1) {
			return result;
		}
		
		usleep(10000);
	}
	
	fprintf(stderr, "rs_readbyte timeouted\n");
	exit(CHIPERROR);
}

void cmd_reset() {
	unsigned char status;
	
	rs_flush();
	rs_writebyte(0xC1); // Reset, regular speed
	status = rs_readbyte();
	
	if ((status & 0xCC) != 0xCC || (status & 0x10) != 0x00) {
		fprintf(stderr, "Invalid response to 1-wire reset: 0x%02x\n", status);
		exit(CHIPERROR);
	}
	
	int state = status & 0x03;
	
	switch(state) {
		case 0:
			fprintf(stderr, "1-wire bus is shorted\n");
			exit(BUSERROR);
		
		case 1:
		case 2:
			fprintf(stderr, "Presence pulse detected\n");
			return;
		
		case 3:
			fprintf(stderr, "No presence pulse\n");
			return;
	}
}

void ow_businit() {
	rs_writebyte(DS2480B_CMDMODE);
	
	cmd_reset();
}

int main(int argc, char *argv[]) {
	if (argc != 2) {
		fprintf(stderr, "Usage: %s <device>, where device is the serial device of ds2480b\n", argv[0]);
	}
	
	ow_init(argv[1]);
	
	ow_businit();
	
	return 0;
}