xmodem.c

串口通讯的XModem协议源码

/*
	Copyright 2001, 2002 Georges Menie (www.menie.org)

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/* this code needs standard functions memcpy() and memset()
   and input/output functions port_inbyte() and port_outbyte().

   the prototypes of the input/output functions are:
     int port_inbyte(unsigned short timeout); // msec timeout
     void port_outbyte(int c);

 */

#include "crc16.h"

#define SOH  0x01
#define STX  0x02
#define EOT  0x04
#define ACK  0x06
#define NAK  0x15
#define CAN  0x18
#define CTRLZ 0x1A

#define DLY_1S 1000
#define MAXRETRANS 25
static int last_error = 0;
/****************Portting Start *******************/
#include "string.h"

void port_outbyte(unsigned char trychar)
{
	unsigned char buf[2];
	buf[0] = trychar;
	lowLevel_write(buf,1);
}

unsigned char port_inbyte(unsigned int time_out)
{
	unsigned char ch;
	int i;
	last_error = 0;

	if(lowLevel_read(&ch,1) == 1)
		return ch;

	last_error = 1;
	return ch;
}
/****************Portting End*******************/
static int check(int crc, const unsigned char *buf, int sz)
{
	if (crc) 
	{
		unsigned short crc = crc16_ccitt(buf, sz);
		unsigned short tcrc = (buf[sz]<<8)+buf[sz+1];
		if (crc == tcrc)
			return 1;
	}
	else 
	{
		int i;
		unsigned char cks = 0;
		for (i = 0; i < sz; ++i) 
		{
			cks += buf[i];
		}
		if (cks == buf[sz])
		return 1;
	}

	return 0;
}

static void flushinput(void)
{
	//while (port_inbyte(((DLY_1S)*3)>>1) >= 0)
		;
}

int xmodemReceive(unsigned char *dest, int destsz)
{
	unsigned char xbuff[1030]; /* 1024 for XModem 1k + 3 head chars + 2 crc + nul */
	unsigned char *p;
	int bufsz, crc = 0;
	unsigned char trychar = 'C';
	unsigned char packetno = 1;
	int i, c, len = 0;
	int retry, retrans = MAXRETRANS;

	for(;;) 
	{
		for( retry = 0; retry < 16; ++retry) 
		{
			if (trychar) 
				port_outbyte(trychar);
			c = port_inbyte((DLY_1S)<<1);
			if (last_error == 0) 
			{
				switch (c) 
				{
					case SOH:
						bufsz = 128;
						goto start_recv;
					case STX:
						bufsz = 1024;
						goto start_recv;
					case EOT:
						flushinput();
						port_outbyte(ACK);
						return len; /* normal end */
					case CAN:
						c = port_inbyte(DLY_1S);

						if (c == CAN) 
						{
							flushinput();
							port_outbyte(ACK);
							return -1; /* canceled by remote */
						}
						break;
					default:
						break;
				}
			}
		}
		if (trychar == 'C') 
		{ 
			trychar = NAK; 
			continue; 
		}
		flushinput();
		port_outbyte(CAN);
		port_outbyte(CAN);
		port_outbyte(CAN);
		return -2; /* sync error */

	start_recv:
		if (trychar == 'C') crc = 1;
		trychar = 0;
		p = xbuff;
		*p++ = c;
		for (i = 0;  i < (bufsz+(crc?1:0)+3); ++i) 
		{
			c = port_inbyte(DLY_1S);

			if (last_error != 0) 
				goto reject;
			*p++ = c;
		}

		if (xbuff[1] == (unsigned char)(~xbuff[2]) && 
			(xbuff[1] == packetno || xbuff[1] == (unsigned char)packetno-1) &&
			check(crc, &xbuff[3], bufsz)) 
		{
			if (xbuff[1] == packetno)	
			{
				int count = destsz - len;
				if (count > bufsz) 
					count = bufsz;
				if (count > 0) 
				{
					memcpy (&dest[len], &xbuff[3], count);
					len += count;
				}
				++packetno;
				retrans = MAXRETRANS+1;
			}
			if (--retrans <= 0) 
			{
				flushinput();
				port_outbyte(CAN);
				port_outbyte(CAN);
				port_outbyte(CAN);
				return -3; /* too many retry error */
			}
			port_outbyte(ACK);
			continue;
		}
	reject:
		flushinput();
		port_outbyte(NAK);
	}
}

int xmodemTransmit(unsigned char *src, int srcsz)
{
	unsigned char xbuff[1030]; /* 1024 for XModem 1k + 3 head chars + 2 crc + nul */
	int bufsz, crc = -1;
	unsigned char packetno = 1;
	int i, c, len = 0;
	int retry;

	for(;;) {
		for( retry = 0; retry < 16; ++retry) 
		{
			c = port_inbyte((DLY_1S)<<1);
			if (last_error == 0) 
			{
				switch (c) 
				{
					case 'C':
						crc = 1;
						goto start_trans;
					case NAK:
						crc = 0;
						goto start_trans;
					case CAN:
						c = port_inbyte(DLY_1S);
						if (c == CAN) 
						{
							port_outbyte(ACK);
							flushinput();
							return -1; /* canceled by remote */
						}
						break;
					default:
						break;
				}
			}
		}
		port_outbyte(CAN);
		port_outbyte(CAN);
		port_outbyte(CAN);
		flushinput();
		return -2; /* no sync */

		for(;;) 
		{
		start_trans:
			xbuff[0] = SOH; bufsz = 128;
			xbuff[1] = packetno;
			xbuff[2] = ~packetno;
			c = srcsz - len;
			if (c > bufsz) c = bufsz;
			if (c >= 0) 
			{
				memset (&xbuff[3], 0, bufsz);
				if (c == 0) 
				{
					xbuff[3] = CTRLZ;
				}
				else 
				{
					memcpy (&xbuff[3], &src[len], c);
					if (c < bufsz) xbuff[3+c] = CTRLZ;
				}
				if (crc) 
				{
					unsigned short ccrc = crc16_ccitt(&xbuff[3], bufsz);
					xbuff[bufsz+3] = (ccrc>>8) & 0xFF;
					xbuff[bufsz+4] = ccrc & 0xFF;
				}
				else 
				{
					unsigned char ccks = 0;
					for (i = 3; i < bufsz+3; ++i) 
					{
						ccks += xbuff[i];
					}
					xbuff[bufsz+3] = ccks;
				}
				for (retry = 0; retry < MAXRETRANS; ++retry) 
				{
					for (i = 0; i < bufsz+4+(crc?1:0); ++i) 
					{
						port_outbyte(xbuff[i]);
					}
					c = port_inbyte(DLY_1S);
					if (last_error == 0 ) 
					{
						switch (c) 
						{
							case ACK:
								++packetno;
								len += bufsz;
								goto start_trans;
							case CAN:
								c = port_inbyte(DLY_1S);
								if ( c == CAN) 
								{
									port_outbyte(ACK);
									flushinput();
									return -1; /* canceled by remote */
								}
								break;
							case NAK:
							default:
								break;
						}
					}
				}
				port_outbyte(CAN);
				port_outbyte(CAN);
				port_outbyte(CAN);
				flushinput();
				return -4; /* xmit error */
			}
			else 
			{
				for (retry = 0; retry < 10; ++retry) 
				{
					port_outbyte(EOT);
					c = port_inbyte((DLY_1S)<<1);
					if (c == ACK) break;
				}
				flushinput();
				return (c == ACK)?len:-5;
			}
		}
	}
}