/*
XMODEM文件傳輸
在某些場合需要用到PC與串口進行文件傳輸的功能，例如PC通過串口升級單片機程序，單片機把采集到的數據以文件形式提供給PC等。
對于使用串口傳輸文件，可以使用自定義的協議，也有一些標準的協議可以使用。使用標準協議的好處是，可以在一些通用的軟件里使用，而不必單獨編寫特定軟件，例如windows自帶的超級終端等。

這里提供兩個函數
xmodem_rx和xmodem_tx，分別用于從PC接收文件和發送文件到PC。
*/


#include <reg52.h>
#include <string.h>
#include <intrins.h>
#include <stdio.h>
#include <absacc.h>
typedef unsigned char    UCHAR;
typedef unsigned int     UINT;
typedef unsigned long    ULONG;

//XMODEM
/*
Xmodem Frame form:    <SOH><blk><255-blk><--128 data bytes--><CRC hi><CRC lo>
1K-Xmodem Frame form: <SOH><blk><255-blk><--1024 data bytes--><CRC hi><CRC lo>
*/
#define XMODEM_SOH 0x01
#define XMODEM_STX 0x02
#define XMODEM_EOT 0x04
#define XMODEM_ACK 0x06
#define XMODEM_NAK 0x15
#define XMODEM_CAN 0x18 // Cancel


//XMODEM協議有兩種，一種是一幀傳輸128字節，一種是一幀1024字節，
//如果系統RAM小，可以用前一種
#define USE_1K_XMODEM 0  /* 1 for use 1k_xmodem, 0 for xmodem */
#if (USE_1K_XMODEM)  //for 1K xmodem protocol
  #define XMODEM_DATA_SIZE 1024
  #define XMODEM_HEAD 0x02
#else    //for Xmodem protocol
  #define XMODEM_DATA_SIZE 128
  #define XMODEM_HEAD 0x01
#endif
UCHAR  xdata frame_data[256];
UCHAR  pack_counter;
//XMODEM協議里，只用一個byte來表示幀序號，超過255就會回到0，
//如果要傳輸大點的文件，必須自己再加一個額外的變量來保存真實序號            
UINT  real_pack_counter;   
// Table of CRC constants - implements x^16+x^12+x^5+1
UINT code crc16_tab[] = {
    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
    0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
    0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
    0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
    0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
    0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
    0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
    0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
    0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
    0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
    0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
    0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
    0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
    0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
    0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
    0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
    0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
    0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
    0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
    0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
    0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
    0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
    0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
    0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
    0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
    0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
    0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
    0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
    0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
    0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
    0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0,
};

// 從串口接收一字節
UCHAR serial_get_char(void)
{
UCHAR cTm;
while(!RI0);
cTm = SBUF0;
RI = 0;
return cTm;
}
// 向串口發送一字節
void serial_put_char(UCHAR c)
{
while(!TI0);
TI = 0;
SBUF = c;
}
// 等串口有數據
// 返回0=無數據,1=有數據
I8_T WaitChar(int tn)
{
unsigned long ulTmo;
while(tn--)
{
  for (ulTmo=0; ulTmo<40000; ulTmo++)
  {
   if (RI)return 1;
  }
}
return 0;
}

// 接收數據幀
int GetRecord(unsigned char blocknum, unsigned char *dest)
{
UCHAR nextChar;
I16_T size;
UINT chk;
nextChar = serial_get_char();
if (nextChar != (255-blocknum)){
  return 0;
}
chk = 0;
for (size = 0; size < XMODEM_DATA_SIZE; ++size){
  nextChar = serial_get_char();
  chk = crc16_tab[((chk>>8) ^ nextChar) & 0xFF] ^ (chk << 8);
  if((real_pack_counter & 0x01) == 1)
   dest[size] = nextChar;
  else
   dest[size + 128] = nextChar;
}
nextChar = serial_get_char();
if (nextChar != ((chk >> 8) & 0xFF))
  return 0;
nextChar = serial_get_char();
if (nextChar != (chk& 0xFF))
  return 0;
return 1;
}
#define INVALID_STATE 0
#define WAITING_START 1
#define WAIT_SOH 2
#define RX_PACKET 3
#define RX_EOT 4
#define SEND_NAK 5
// xmodem協議接收文件
I8_T xmodem_rx(void)
{
I8_T ntry;
I8_T state;
UCHAR nextChar;
ntry = 0;
pack_counter = 1;
real_pack_counter = 1;
state = WAITING_START;
while(1){
  switch(state){
   case WAITING_START:   // 請求傳送
    serial_put_char('C'); // 發送請求符
    if (WaitChar(3)){
     nextChar = serial_get_char(); // 接收幀頭
     if (nextChar == XMODEM_HEAD){
      state = RX_PACKET;  // 收到幀頭
     }
    }
    break;
   case WAIT_SOH: // 等幀頭
    nextChar = serial_get_char(); // 收幀頭
    if (nextChar == XMODEM_HEAD){
     state = RX_PACKET;
    }
    else if (nextChar == XMODEM_EOT){ // 收到終止符
     state = RX_EOT;
     serial_put_char(XMODEM_ACK); // 回送應答符
     return (1);      // 結束
    }
    else if (nextChar == XMODEM_CAN){ // 取消
     return (1);
    }
    break;
   case RX_PACKET:  // 收幀
    nextChar = serial_get_char();  // 收幀計數
    if (nextChar != pack_counter){  // 幀計數是否正確   
     serial_put_char(XMODEM_CAN); // 不正確,取消傳送
     serial_put_char(XMODEM_CAN);
     serial_put_char(XMODEM_CAN);
     serial_put_char(XMODEM_CAN);
     return (-1);
    }
    if (GetRecord(pack_counter, frame_data)){ //收數據   
      
      /*在此處增加用戶對接收數據幀的處理程序*/
     ++pack_counter;
     ++real_pack_counter;      // 計數加1
     ntry = 0;   
     state = WAIT_SOH;      // 等下一個幀
     serial_put_char(XMODEM_ACK);   // 發送應答
    }
    else // 收數據錯誤
    {
     if (++ntry >9){ // 錯誤次數超出限制   
      serial_put_char(XMODEM_CAN); // 取消傳送
      serial_put_char(XMODEM_CAN);
      serial_put_char(XMODEM_CAN);
      serial_put_char(XMODEM_CAN);
      return (-1);
     }
     state = WAIT_SOH;
     serial_put_char(XMODEM_NAK); // 請求重傳
    }
    break;
   default:
    break;
  }
}
return 0;
}

// 發送數據幀
void SendRecord(unsigned char * buff)
{
unsigned int chk;
int i;
serial_put_char(XMODEM_HEAD);
serial_put_char(pack_counter);
serial_put_char(255-pack_counter);
chk = 0;
for(i=0; i < XMODEM_DATA_SIZE; ++i)
{
  chk = crc16_tab[((chk>>8) ^ buff) & 0xFF] ^ (chk << 8);
  serial_put_char(buff);
}
serial_put_char((chk >> 8));
serial_put_char(chk);
}
// xmodem協議發送文件
// 收到請求符"C"后進入此函數
int xmodem_tx(void)
{
char complete,retry_num;
unsigned char ack_id;
ack_id = XMODEM_ACK;
pack_counter = 0;
real_pack_counter = 0;
complete = 0;
while (complete == 0)
{
  switch (ack_id)
  {
   case XMODEM_ACK:   // 正確應答
    retry_num = 0;
    pack_counter ++;
    real_pack_counter ++;
    memset(frame_data,0,XMODEM_DATA_SIZE);  // 緩沖區清零
   
   
   
    if (real_pack_counter <= 16384) // 從flash讀取數據到緩沖區
    {
     
     /*在此處加入用戶讀數據到緩沖區的代碼*/
     
     SendRecord(frame_data);   // 發送數據幀
     ack_id = serial_get_char();  // 等應答
     break;
    }
    else // 數據已傳送完
    {
     ack_id = XMODEM_EOT;
                    complete = 1;
     while(ack_id != XMODEM_ACK)  //Waiting for complete ACK
     {
      serial_put_char(XMODEM_EOT);
      ack_id = serial_get_char();
     }
     break;
    }
    break;
   case XMODEM_NAK: // 請求重發
    if( retry_num++ > 10) //Retry too many times
    {
     complete = 1;
     serial_put_char(XMODEM_CAN);
     serial_put_char(XMODEM_CAN);
     serial_put_char(XMODEM_CAN);
     serial_put_char(XMODEM_CAN);
    }
    else
    {
     SendRecord(frame_data); // 重發
     ack_id = serial_get_char();
    }
    break;
   default:
    complete = 1;
    serial_put_char(XMODEM_CAN);
    serial_put_char(XMODEM_CAN);
    serial_put_char(XMODEM_CAN);
    serial_put_char(XMODEM_CAN);
    break;
  }
}
return 0;
}