xmit115200.c

一款MP3 Player Firmware 的原代码,非常有参考价值

/* Transmit a fast binary download to the mp3 player at 115200 baud.
 * This program takes care of switching the baud rate details:
 *    1: Command the board to begin a fast flash download
 *    2: Command the board to switch to 115200
 *    3: Switch the PC to 115200
 *    4: Transmit the data at 115200
 *    5: Switch back to original baud rate at end of transfer.
 * It is assumed that the user is running a terminal emulator program
 * while this download is in progress.  The terminal emulator program
 * is responsible for establishing the baud rate to 19200 before this
 * download utility is run.
 *
 * The serial port to download to defaults to /dev/ttyS0, the first
 * serial port.  The port can be changed on the command line ie.
 * xmit115200 /dev/ttyS2 or as an environment variable PJRCMP3_PORT.
 *
 * This code uses the unix/posix termios interface, and other unix
 * APIs, and it also depends on the ability to open the serial port
 * for writing while it's already in use by the terminal emulation
 * program.  Works great on Linux (tested on RedHat 7.2), but it's
 * very unlikely to ever be ported to Microsoft Windows.
 *
 *  Compile with:
 *     gcc -O2 -Wall -o xmit115200 xmit115200.c 
 *
 *  Typical usage:
 *     ./hex2fdl mp3player.hex | ./xmit115200
 */


#define PORT "/dev/ttyS0"



#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <signal.h>


void ctrl_c_handler(int num);

int port;
struct termios orig_settings;


int main(int argc, char **argv)
{
	int n;
	struct termios tty_settings;
	unsigned char buf[256];
	unsigned char baud_change_cmd[2] = {0x6A, 0xB4};
	char* portstr = PORT;


	if (argc == 2)
	{
		portstr = argv[1];
	}
	else if (getenv("PJRCMP3_PORT") != 0)
	{
		portstr = strdup(getenv("PJRCMP3_PORT"));
	}

	/* first, open the serial port for writing */
	port = open(portstr, O_WRONLY | O_NOCTTY);
	if (port < 0) {
		fprintf(stderr, "Unable to open \"%s\"\n", portstr);
		exit(1);
	}

	/* send the command to start the fast flash download */
	write(port, "~", 1);
	usleep(70000);

	/* send the command to change the baud rate... */
	/* we'll assume there's a terminal emulator running with */
	/* this port open and the baud rate configured nicely */
	write(port, baud_change_cmd, 2);
	usleep(20000);

	/* now switch to 115200 baud */
	tcgetattr(port, &tty_settings);
	memcpy(&orig_settings, &tty_settings, sizeof(struct termios));
	signal(SIGINT, ctrl_c_handler);
	cfsetospeed(&tty_settings, B115200);
	tcsetattr(port, 0, &tty_settings);

	/* copy all data from stdin to the serial port, at 115200 :) */
	while (1) {
		n = read(fileno(stdin), buf, sizeof(buf));
		if (n == 0) break;
		if (n < 0) {
			if (errno == EINTR) continue;
			fprintf(stderr, "error reading input\n");
			tcflush(port, TCIOFLUSH);
			tcsetattr(port, 0, &orig_settings);
			write(port, "\033", 1);
			exit(1);
		}
		write(port, buf, n);
	}

	/* wait for all this data we're transmitted to actually */
	/* leave the port and get into the mp3 player */
	tcdrain(port);
	usleep(20000);

	/* now restore the baud rate, hopefully before the board */
	/* begins printing the download summary! */
	tcsetattr(port, 0, &orig_settings);


	return 0;
}



void ctrl_c_handler(int num)
{
	tcflush(port, TCIOFLUSH);
	tcsetattr(port, 0, &orig_settings);
	usleep(10000);
	write(port, "\033", 1);
	printf("xmit115200: abort on ctrl-c, baud rate restored\n");
	exit(1);
}