xmodem.c

Boot code for ADM5120 with serial console for Edimax router.

/*****************************************************************************
;
;    Project : Common Platform
;    Creator : Sumei Chung
;    File    : xmodem.C
;    Abstract: 
;
;*****************************************************************************/

#include "xmodem.h"

#ifndef FALSE
#define FALSE   0
#endif

#ifndef TRUE
#define TRUE    1
#endif

extern void buart_put(char);
extern int buart_get(int);


/*--------------------------------------------------------------
 * read_packet	                            
 *		Get XMODEM_SIZE bytes from uart.  Timeout if 3
 *		seconds elapse
 *
 * INPUT:
 *		char *buf   -- buffer to read the packet
 *
 * RETURN:
 *		0    -- OK
 *		-1   -- error
 *--------------------------------------------------------------*/
static int read_packet(char *buf) 
{
    register int i;         /* Number of characters read */
    register int c;         /* Next character read */
    register unsigned char chksum;   /* accumulate checksum here */

    chksum = 0;

	for (i = 0; i < XMODEM_SIZE; i++ ) {
		if ((c = buart_get(3)) == -1) {
			return -1;
		} else {
			buf[i] = c;
			chksum += c;
		}
	}

	/* Read and confirm checksum */
	if ((c = buart_get(3)) == -1) {
		return -1;
	} else if ((c & 0xff) != chksum) {
		/* chksum error, abort */
		return -1;
	}

	return 0;
}


/*--------------------------------------------------------------
 * xmodem	                            
 *		Get XMODEM_SIZE bytes from uart.  Timeout if 3
 *		seconds elapse
 *
 * INPUT:
 *		char *buf   -- buffer to read the packet
 *
 * RETURN:
 *		 0   -- OK
 *		-1   -- error
 *--------------------------------------------------------------*/
int xmodem(char *buf, int buf_size)
{
    register int c=0;                /* 1st byte of packet */
    register int errors;             /* Running count of errors */
    register int errorflag;          /* True when error found while reading a packet    */
    register int fatalerror;         /* True when fatal error found while reading packet */
    register unsigned char pktnum;   /* 2nd byte of packet: packet # (mod 128) */
    register unsigned char pktchk;   /* 3rd byte of packet: should be complement ofpktnum*/
    register int pktcnt;             /* total # of packets received so far */
    register int initial_tries;

    register char *buf_end = buf + buf_size;
    register char *working = buf;

    fatalerror = FALSE;
    errors = pktcnt = 0;

	/*
     * start communications by providing NAK to the sending
     * end.  The number and time over which these are provided
     * is 10 seconds at once per second, followed by about
     * one minute at 4 second intervals.  the maximum tolerable
     * inter-character time is 3 seconds, and if that occurs,
     * we will wait for 1 second of silence from the host and
     * then NAK the packet.
	 */

    initial_tries = 10;

    do {
        buart_put (NAK);
    } while (--initial_tries && ((c = buart_get (1)) == -1));

    goto PreLoaded;		/* UGH */	/* INTO THE MIDDLE OF A DO LOOP ??? */

    /* MAIN Do-While loop to read packets */

    do {
        /* start by read first byte in packet */
        c = buart_get (3);

PreLoaded:	/* UGH */

        errorflag = FALSE;

		switch (c) {
			case -1:
				errorflag = TRUE;
				break;
			case ACK:       /* transmitter confirms reception */
				if (pktcnt > 0)
					continue;
				break;
			case EOT:       /* transmitter signals finish */
				if ((c = buart_get (1)) == -1)
					c = EOT;
				else if (c != EOT) {
					/* EOT from data portion of a (delayed) packet */
					c = -1;
					errorflag = TRUE;
				}
				break;
			case CAN:       /* bailing out? */
				if ((buart_get (3) & 0x7f) != CAN)
					errorflag = TRUE;
				else
					fatalerror = TRUE;
				break;
			case SOH:       /* start reading packet */
				pktnum = buart_get (3);
				pktchk = buart_get (3);

				if (pktnum != ((unsigned char)~pktchk)) {
					/* MISREAD PACKET # */
					errorflag = TRUE;
					break;
				}

				if (pktnum == (pktcnt & 0xff)) {
					/* DUPLICATE PACKET -- DISCARD */
					while (buart_get(3) != -1)
						;

					buart_put (ACK);
					break;
				}

				if (pktnum != ((pktcnt+1) & 0xff)) {
					/* PHASE ERROR */
					fatalerror = TRUE;
					break;
				}

				/* Read the 128-byte data packet and */
				/* calculate checksum for the packet */

				if (read_packet(working) != 0) {
					errorflag = TRUE;
					break;
				}

				/* increment the memory pointer  */
				if (working >= buf_end) {
					fatalerror = TRUE;
					break;
				}

				working += XMODEM_SIZE;
				errors = 0;
				pktcnt++;

				/* ACK the packet */
				buart_put (ACK);
				break;
			default:
				continue;
		}	/* end of switch */

		/* check on errors or batch transfers */
		if (errorflag || pktcnt == 0) {
			if (errorflag) {
				if (++errors >= ERRORMAX)
					fatalerror = TRUE;
			}

			if (!fatalerror) {
				/* wait for line to settle */
				while (buart_get(1) != -1)
					;

				buart_put(NAK);
			}
		}
	} while (c != EOT && !fatalerror);	// end of do() loop

	/*************************
	 *	End of transmission 
	 **************************/

	if (c == EOT)
		buart_put (ACK);
	else {
		/* error exit */
		if (pktcnt != 0) {
			/* Cancel download by sending two CAN to remote */
			buart_put(CAN);
			buart_put(CAN);
		}
	}

	/***********************************
	 *	Now wait for line settle down
	 ***********************************/

	while (buart_get(2) != -1)
		;

	if (fatalerror)
		return -1;

	return (pktcnt * XMODEM_SIZE);
}