论坛首页 › 通信 › 在这个论坛里为什么搜不到“Xmodem”的任何信息呢？

huamao0086 发表于 2011-10-11 22:24:35

在这个论坛里为什么搜不到“Xmodem”的任何信息呢？

串口通信协议，请教高人了

上源码：（我看不懂，谁给加下注释，尤其是接收函数里面）

XModem 源码

#include "crc16.h"

#define SOH0x01
#define STX0x02
#define EOT0x04
#define ACK0x06
#define NAK0x15
#define CAN0x18
#define CTRLZ 0x1A

#define DLY_1S 1000
#define MAXRETRANS 25
static int last_error = 0;

#include "string.h"

void port_outbyte(unsigned char trychar)
{
unsigned char buf;
buf = 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;
}

static int check(int crc, const unsigned char *buf, int sz)
{
if (crc)
{
unsigned short crc = crc16_ccitt(buf, sz);
unsigned short tcrc = (buf<<8)+buf;
if (crc == tcrc)
   return 1;
}
else
{
int i;
unsigned char cks = 0;
for (i = 0; i < sz; ++i)
{
   cks += buf;
}
if (cks == buf)
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;
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;
   case CAN:
      c = port_inbyte(DLY_1S);

      if (c == CAN)
      {
       flushinput();
       port_outbyte(ACK);
       return -1;
      }
      break;
   default:
      break;
    }
   }
}
if (trychar == 'C')
{
   trychar = NAK;
   continue;
}
flushinput();
port_outbyte(CAN);
port_outbyte(CAN);
port_outbyte(CAN);
return -2;

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

int xmodemTransmit(unsigned char *src, int srcsz)
{
unsigned char xbuff;
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;
      }
      break;
   default:
      break;
    }
   }
}
port_outbyte(CAN);
port_outbyte(CAN);
port_outbyte(CAN);
flushinput();
return -2;

for(;;)
{
start_trans:
   xbuff = SOH; bufsz = 128;
   xbuff = packetno;
   xbuff = ~packetno;
   c = srcsz - len;
   if (c > bufsz) c = bufsz;
   if (c >= 0)
   {
    memset (&xbuff, 0, bufsz);
    if (c == 0)
    {
   xbuff = CTRLZ;
    }
    else
    {
   memcpy (&xbuff, &src, c);
   if (c < bufsz) xbuff = CTRLZ;
    }
    if (crc)
    {
   unsigned short ccrc = crc16_ccitt(&xbuff, bufsz);
   xbuff = (ccrc>>8) & 0xFF;
   xbuff = ccrc & 0xFF;
    }
    else
    {
   unsigned char ccks = 0;
   for (i = 3; i < bufsz+3; ++i)
   {
      ccks += xbuff;
   }
   xbuff = ccks;
    }
    for (retry = 0; retry < MAXRETRANS; ++retry)
    {
   for (i = 0; i < bufsz+4+(crc?1:0); ++i)
   {
      port_outbyte(xbuff);
   }
   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;
      }
      break;
       case NAK:
       default:
      break;
      }
   }
    }
    port_outbyte(CAN);
    port_outbyte(CAN);
    port_outbyte(CAN);
    flushinput();
    return -4;
   }
   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;
   }
}
}
}

huamao0086 发表于 2011-11-3 16:52:46

妈的，老子已经玩通Xmodem了，就等着有人来跪求了

dishao 发表于 2011-11-8 15:08:15

比I2C还简单的协议有什么可炫耀的。

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