xmodem_8c-source.html

avr cpu 库源代码 对avr单片机编程很有帮助

00124         {
00125             <span class="comment">// is this the packet we were waiting for?</span>
00126             <span class="keywordflow">if</span>(xmbuf[1] == seqnum)
00127             {
00128                 <span class="comment">// write/deliver data</span>
00129                 write(&amp;xmbuf[3], pktsize);
00130                 <span class="comment">//spiflashWrite(flashaddr, pktsize, &amp;xmbuf[3]);</span>
00131                 totalbytes += pktsize;
00132                 <span class="comment">// next sequence number</span>
00133                 seqnum++;
00134                 <span class="comment">// reset retries</span>
00135                 retry = XMODEM_RETRY_LIMIT;
00136                 <span class="comment">// reply with ACK</span>
00137                 response = ACK;
00138                 <span class="keywordflow">continue</span>;
00139             }
00140             <span class="keywordflow">else</span> <span class="keywordflow">if</span>(xmbuf[1] == (<span class="keywordtype">unsigned</span> char)(seqnum-1))
00141             {
00142                 <span class="comment">// this is a retransmission of the last packet</span>
00143                 <span class="comment">// ACK and move on</span>
00144                 response = ACK;
00145                 <span class="keywordflow">continue</span>;
00146             }
00147             <span class="keywordflow">else</span>
00148             {
00149                 <span class="comment">// we are completely out of sync</span>
00150                 <span class="comment">// cancel transmission</span>
00151                 <a class="code" href="group__xmodem.html#ga5">xmodemInFlush</a>();
00152                 xmodemOut(CAN);
00153                 xmodemOut(CAN);
00154                 xmodemOut(CAN);
00155                 <span class="keywordflow">return</span> XMODEM_ERROR_OUTOFSYNC;
00156             }
00157         }
00158         <span class="keywordflow">else</span>
00159         {
00160             <span class="comment">// packet was corrupt</span>
00161             <span class="comment">// NAK it and try again</span>
00162             retry--;
00163             <a class="code" href="group__xmodem.html#ga5">xmodemInFlush</a>();
00164             response = NAK;
00165             <span class="keywordflow">continue</span>;
00166         }
00167     }
00168 
00169     <span class="comment">// exceeded retry count</span>
00170     <a class="code" href="group__xmodem.html#ga5">xmodemInFlush</a>();
00171     xmodemOut(CAN);
00172     xmodemOut(CAN);
00173     xmodemOut(CAN);
00174     <span class="keywordflow">return</span> XMODEM_ERROR_RETRYEXCEED;
00175 }
00176 
00177 
<a name="l00178"></a><a class="code" href="group__xmodem.html#ga2">00178</a> <span class="keywordtype">long</span> <a class="code" href="group__xmodem.html#ga2">xmodemTransmit</a>( <span class="keywordtype">int</span> (*read)(<span class="keywordtype">unsigned</span> <span class="keywordtype">char</span>* buffer, <span class="keywordtype">int</span> size) )
00179 {
00180     <span class="comment">// still to be written</span>
00181     <span class="keywordflow">return</span> 0;
00182 }
00183 
00184 uint16_t crc_xmodem_update(uint16_t crc, uint8_t data)
00185 {
00186     <span class="keywordtype">int</span> i;
00187 
00188     crc = crc ^ ((uint16_t)data &lt;&lt; 8);
00189     <span class="keywordflow">for</span> (i=0; i&lt;8; i++)
00190     {
00191         <span class="keywordflow">if</span>(crc &amp; 0x8000)
00192             crc = (crc &lt;&lt; 1) ^ 0x1021;
00193         <span class="keywordflow">else</span>
00194             crc &lt;&lt;= 1;
00195     }
00196 
00197     <span class="keywordflow">return</span> crc;
00198 }
00199 
<a name="l00200"></a><a class="code" href="group__xmodem.html#ga3">00200</a> <span class="keywordtype">int</span> <a class="code" href="group__xmodem.html#ga3">xmodemCrcCheck</a>(<span class="keywordtype">int</span> crcflag, <span class="keyword">const</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> *buffer, <span class="keywordtype">int</span> size)
00201 {
00202     <span class="comment">// crcflag=0 - do regular checksum</span>
00203     <span class="comment">// crcflag=1 - do CRC checksum</span>
00204 
00205     <span class="keywordflow">if</span>(crcflag)
00206     {
00207         <span class="keywordtype">unsigned</span> <span class="keywordtype">short</span> crc=0;
00208         <span class="keywordtype">unsigned</span> <span class="keywordtype">short</span> pktcrc = (buffer[size]&lt;&lt;8)+buffer[size+1];
00209         <span class="comment">// do CRC checksum</span>
00210         <span class="keywordflow">while</span>(size--)
00211             crc = crc_xmodem_update(crc, *buffer++);
00212         <span class="comment">// check checksum against packet</span>
00213         <span class="keywordflow">if</span>(crc == pktcrc)
00214             <span class="keywordflow">return</span> 1;
00215     }
00216     <span class="keywordflow">else</span>
00217     {
00218         <span class="keywordtype">int</span> i;
00219         <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> cksum = 0;
00220         <span class="comment">// do regular checksum</span>
00221         <span class="keywordflow">for</span>(i=0; i&lt;size; ++i)
00222         {
00223             cksum += buffer[i];
00224         }
00225         <span class="comment">// check checksum against packet</span>
00226         <span class="keywordflow">if</span>(cksum == buffer[size])
00227             <span class="keywordflow">return</span> 1;
00228     }
00229 
00230     <span class="keywordflow">return</span> 0;
00231 }
00232 
00233 
<a name="l00234"></a><a class="code" href="group__xmodem.html#ga4">00234</a> <span class="keywordtype">int</span> <a class="code" href="group__xmodem.html#ga4">xmodemInTime</a>(<span class="keywordtype">unsigned</span> <span class="keywordtype">short</span> timeout)
00235 {
00236     <span class="keywordtype">int</span> c=-1;
00237 
00238     <span class="keywordflow">while</span>( (timeout--) &amp;&amp; ((c=xmodemIn()) &lt; 0) )
00239         <a class="code" href="group__timer.html#ga10">timerPause</a>(1);
00240 
00241     <span class="keywordflow">return</span> c;
00242 }
00243 
<a name="l00244"></a><a class="code" href="group__xmodem.html#ga5">00244</a> <span class="keywordtype">void</span> <a class="code" href="group__xmodem.html#ga5">xmodemInFlush</a>(<span class="keywordtype">void</span>)
00245 {
00246     <span class="keywordflow">while</span>(<a class="code" href="group__xmodem.html#ga4">xmodemInTime</a>(XMODEM_TIMEOUT_DELAY) &gt;= 0);
00247 }
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