bitbang.c

这是一个非常有价值的参考代码

/*
 * avrdude - A Downloader/Uploader for AVR device programmers
 * Copyright (C) 2000, 2001, 2002, 2003  Brian S. Dean <[e-mail]>
 * Copyright (C) 2005 Michael Holzt <[e-mail]>
 *
 * 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 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 General Public License for more details.
 *
 * You should have received a copy of the GNU 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
 */
/* $Id: bitbang.c,v 1.1 2005/09/18 20:12:23 joerg_wunsch Exp $ */

#include "ac_cfg.h"

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

#include "avr.h"
#include "pindefs.h"
#include "pgm.h"
#include "par.h"
#include "serbb.h"

#define SLOW_TOGGLE 0

extern char * progname;
extern int do_cycles;
extern int verbose;

static int bitbang_setpin(PROGRAMMER * pgm, int pin, int value)
{
  if ( pgm->flag )
    serbb_setpin(pgm->fd,pin,value);
  else
    par_setpin(pgm->fd,pin,value);

  return 0;
}


static int bitbang_getpin(PROGRAMMER * pgm, int pin)
{
  if ( pgm->flag )
    return serbb_getpin(pgm->fd,pin);
  else
    return par_getpin(pgm->fd,pin);
}


static int bitbang_highpulsepin(PROGRAMMER * pgm, int pin)
{
  if ( pgm->flag )
    return serbb_highpulsepin(pgm->fd,pin);
  else
    return par_highpulsepin(pgm->fd,pin);
}


/*
 * transmit and receive a byte of data to/from the AVR device
 */
static unsigned char bitbang_txrx(PROGRAMMER * pgm, unsigned char byte)
{
  int i;
  unsigned char r, b, rbyte;

  rbyte = 0;
  for (i=7; i>=0; i--) {
    /*
     * Write and read one bit on SPI.
     * Some notes on timing: Let T be the time it takes to do
     * one bitbang_setpin()-call resp. par clrpin()-call, then
     * - SCK is high for 2T
     * - SCK is low for 2T
     * - MOSI setuptime is 1T
     * - MOSI holdtime is 3T
     * - SCK low to MISO read is 2T to 3T
     * So we are within programming specs (expect for AT90S1200),
     * if and only if T>t_CLCL (t_CLCL=clock period of target system).
     *
     * Due to the delay introduced by "IN" and "OUT"-commands,
     * T is greater than 1us (more like 2us) on x86-architectures.
     * So programming works safely down to 1MHz target clock.
    */

    b = (byte >> i) & 0x01;

    /* set the data input line as desired */
    bitbang_setpin(pgm, pgm->pinno[PIN_AVR_MOSI], b);

    bitbang_setpin(pgm, pgm->pinno[PIN_AVR_SCK], 1);

    /*
     * read the result bit (it is either valid from a previous falling
     * edge or it is ignored in the current context)
     */
    r = bitbang_getpin(pgm, pgm->pinno[PIN_AVR_MISO]);

    bitbang_setpin(pgm, pgm->pinno[PIN_AVR_SCK], 0);

    rbyte |= r << i;
  }

  return rbyte;
}


int bitbang_rdy_led(PROGRAMMER * pgm, int value)
{
  bitbang_setpin(pgm, pgm->pinno[PIN_LED_RDY], !value);
  return 0;
}

int bitbang_err_led(PROGRAMMER * pgm, int value)
{
  bitbang_setpin(pgm, pgm->pinno[PIN_LED_ERR], !value);
  return 0;
}

int bitbang_pgm_led(PROGRAMMER * pgm, int value)
{
  bitbang_setpin(pgm, pgm->pinno[PIN_LED_PGM], !value);
  return 0;
}

int bitbang_vfy_led(PROGRAMMER * pgm, int value)
{
  bitbang_setpin(pgm, pgm->pinno[PIN_LED_VFY], !value);
  return 0;
}


/*
 * transmit an AVR device command and return the results; 'cmd' and
 * 'res' must point to at least a 4 byte data buffer
 */
int bitbang_cmd(PROGRAMMER * pgm, unsigned char cmd[4],
                   unsigned char res[4])
{
  int i;

  for (i=0; i<4; i++) {
    res[i] = bitbang_txrx(pgm, cmd[i]);
  }

    if(verbose >= 2)
	{
        fprintf(stderr, "bitbang_cmd(): [ ");
        for(i = 0; i < 4; i++)
            fprintf(stderr, "%02X ", cmd[i]);
        fprintf(stderr, "] [ ");
        for(i = 0; i < 4; i++)
		{
            fprintf(stderr, "%02X ", res[i]);
		}
        fprintf(stderr, "]\n");
	}

  return 0;
}


/*
 * issue the 'chip erase' command to the AVR device
 */
int bitbang_chip_erase(PROGRAMMER * pgm, AVRPART * p)
{
  unsigned char cmd[4];
  unsigned char res[4];

  if (p->op[AVR_OP_CHIP_ERASE] == NULL) {
    fprintf(stderr, "chip erase instruction not defined for part \"%s\"\n",
            p->desc);
    return -1;
  }

  pgm->pgm_led(pgm, ON);

  memset(cmd, 0, sizeof(cmd));

  avr_set_bits(p->op[AVR_OP_CHIP_ERASE], cmd);
  pgm->cmd(pgm, cmd, res);
  usleep(p->chip_erase_delay);
  pgm->initialize(pgm, p);

  pgm->pgm_led(pgm, OFF);

  return 0;
}

/*
 * issue the 'program enable' command to the AVR device
 */
int bitbang_program_enable(PROGRAMMER * pgm, AVRPART * p)
{
  unsigned char cmd[4];
  unsigned char res[4];

  if (p->op[AVR_OP_PGM_ENABLE] == NULL) {
    fprintf(stderr, "program enable instruction not defined for part \"%s\"\n",
            p->desc);
    return -1;
  }

  memset(cmd, 0, sizeof(cmd));
  avr_set_bits(p->op[AVR_OP_PGM_ENABLE], cmd);
  pgm->cmd(pgm, cmd, res);

  if (res[2] != cmd[1])
    return -2;

  return 0;
}

/*
 * initialize the AVR device and prepare it to accept commands
 */
int bitbang_initialize(PROGRAMMER * pgm, AVRPART * p)
{
  int rc;
  int tries;

  pgm->powerup(pgm);
  usleep(20000);

  bitbang_setpin(pgm, pgm->pinno[PIN_AVR_SCK], 0);
  bitbang_setpin(pgm, pgm->pinno[PIN_AVR_RESET], 0);
  usleep(20000);

  bitbang_highpulsepin(pgm, pgm->pinno[PIN_AVR_RESET]);

  usleep(20000); /* 20 ms XXX should be a per-chip parameter */

  /*
   * Enable programming mode.  If we are programming an AT90S1200, we
   * can only issue the command and hope it worked.  If we are using
   * one of the other chips, the chip will echo 0x53 when issuing the
   * third byte of the command.  In this case, try up to 32 times in
   * order to possibly get back into sync with the chip if we are out
   * of sync.
   */
  if (strcmp(p->desc, "AT90S1200")==0) {
    pgm->program_enable(pgm, p);
  }
  else {
    tries = 0;
    do {
      rc = pgm->program_enable(pgm, p);
      if ((rc == 0)||(rc == -1))
        break;
      bitbang_highpulsepin(pgm, pgm->pinno[p->retry_pulse/*PIN_AVR_SCK*/]);
      tries++;
    } while (tries < 65);

    /*
     * can't sync with the device, maybe it's not attached?
     */
    if (rc) {
      fprintf(stderr, "%s: AVR device not responding\n", progname);
      return -1;
    }
  }

  return 0;
}