stxetx_8c-source.html

avr cpu 库源代码 对avr单片机编程很有帮助

00110         {
00111             <span class="comment">// if this is a start, then get the length</span>
00112             length = <a class="code" href="group__buffer.html#ga4">bufferGetAtIndex</a>(rxBuffer, STXETX_LENGTHOFFSET);
00113 
00114             <span class="comment">// now we must have at least STXETX_HEADERLENGTH+length+STXETX_TRAILERLENGTH in buffer to continue</span>
00115             <span class="keywordflow">if</span>(rxBuffer-&gt;<a class="code" href="structstruct__cBuffer.html#o2">datalength</a> &gt;= ((u16)STXETX_HEADERLENGTH+length+(u16)STXETX_TRAILERLENGTH))
00116             {
00117                 <span class="comment">// check to see if ETX is in the right position</span>
00118                 <span class="keywordflow">if</span>(<a class="code" href="group__buffer.html#ga4">bufferGetAtIndex</a>(rxBuffer, STXETX_HEADERLENGTH+length+STXETX_TRAILERLENGTH-1) == ETX)
00119                 {
00120                     <span class="comment">// found potential packet</span>
00121                     <span class="comment">// test checksum</span>
00122                     checksum = 0;
00123                     <span class="comment">// sum data between STX and ETX, not including checksum itself</span>
00124                     <span class="comment">// (u16) casting needed to avoid unsigned/signed mismatch</span>
00125                     <span class="keywordflow">for</span>(i = 0; i&lt;((u16)STXETX_HEADERLENGTH+length+(u16)STXETX_TRAILERLENGTH-(u16)STXETX_NOETXSTXCHECKSUM); i++)
00126                     {
00127                         checksum += <a class="code" href="group__buffer.html#ga4">bufferGetAtIndex</a>(rxBuffer, i+STXETX_STATUSOFFSET);
00128                     }
00129                     <span class="comment">// compare checksums</span>
00130                     <span class="keywordflow">if</span>(checksum == <a class="code" href="group__buffer.html#ga4">bufferGetAtIndex</a>(rxBuffer, STXETX_CHECKSUMOFFSET+length))
00131                     {
00132                         <span class="comment">//we have a packet!</span>
00133                         foundpacket = TRUE;
00134                     
00135                         <span class="comment">// copy data to buffer</span>
00136                         <span class="comment">// (don't copy STX, ETX, or CHECKSUM)</span>
00137                         <span class="keywordflow">for</span>(i = 0; i &lt; ((u16)STXETX_HEADERLENGTH+length-1); i++)
00138                         {
00139                             stxetxRxPacket[i] = <a class="code" href="group__buffer.html#ga4">bufferGetAtIndex</a>(rxBuffer, i+1);
00140                         }
00141 
00142                         <span class="comment">// debug</span>
00143                         <span class="comment">//rprintf("STXETX Received packet type: 0x%x\n", bufferGetAtIndex(rxBuffer, STXETX_TYPEOFFSET));</span>
00144 
00145                         <span class="comment">// dump this packet from the</span>
00146                         <a class="code" href="group__buffer.html#ga3">bufferDumpFromFront</a>(rxBuffer, STXETX_HEADERLENGTH+length+STXETX_TRAILERLENGTH);
00147 
00148                         <span class="comment">// done with this processing session</span>
00149                         <span class="keywordflow">break</span>;
00150                     }
00151                     <span class="keywordflow">else</span>
00152                     {
00153                         <span class="comment">// checksum bad</span>
00154                         <span class="comment">//rprintf("STXETX Received packet with bad checksum\r\n");</span>
00155                         <span class="comment">// for now, we dump these</span>
00156                         <span class="comment">// dump this STX</span>
00157                         <a class="code" href="group__buffer.html#ga2">bufferGetFromFront</a>(rxBuffer);
00158                     }
00159                 }
00160                 <span class="keywordflow">else</span>
00161                 {
00162                     <span class="comment">// no ETX or ETX in wrong position</span>
00163                     <span class="comment">// dump this STX</span>
00164                     <a class="code" href="group__buffer.html#ga2">bufferGetFromFront</a>(rxBuffer);
00165                 }
00166             }
00167             <span class="keywordflow">else</span>
00168             {
00169                 <span class="comment">// not enough data in buffer to decode pending packet</span>
00170                 <span class="comment">// wait until next time</span>
00171                 <span class="keywordflow">break</span>;
00172             }
00173         }
00174         <span class="keywordflow">else</span>
00175         {
00176             <span class="comment">// this is not a start, dump it</span>
00177             <a class="code" href="group__buffer.html#ga2">bufferGetFromFront</a>(rxBuffer);
00178         }
00179     }
00180 
00181     <span class="comment">// check if receive buffer is full with no packets decoding</span>
00182     <span class="comment">// (ie. deadlocked on garbage data or packet that exceeds buffer size)</span>
00183     <span class="keywordflow">if</span>(!<a class="code" href="group__buffer.html#ga6">bufferIsNotFull</a>(rxBuffer))
00184     {
00185         <span class="comment">// dump receive buffer contents to relieve deadlock</span>
00186         <a class="code" href="group__buffer.html#ga7">bufferFlush</a>(rxBuffer);
00187     }
00188     
00189     <span class="keywordflow">return</span> foundpacket;
00190 }
00191 
<a name="l00192"></a><a class="code" href="group__stxetx.html#ga3">00192</a> <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="group__stxetx.html#ga3">stxetxGetRxPacketStatus</a>(<span class="keywordtype">void</span>)
00193 {
00194     <span class="comment">// return the packet's status</span>
00195     <span class="comment">// (subtract 1 from the offset because the STX has already been discarded)</span>
00196     <span class="keywordflow">return</span> stxetxRxPacket[STXETX_STATUSOFFSET-1];
00197 }
00198 
<a name="l00199"></a><a class="code" href="group__stxetx.html#ga4">00199</a> <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="group__stxetx.html#ga4">stxetxGetRxPacketType</a>(<span class="keywordtype">void</span>)
00200 {
00201     <span class="comment">// return the packet's type</span>
00202     <span class="comment">// (subtract 1 from the offset because the STX has already been discarded)</span>
00203     <span class="keywordflow">return</span> stxetxRxPacket[STXETX_TYPEOFFSET-1];
00204 }
00205 
<a name="l00206"></a><a class="code" href="group__stxetx.html#ga5">00206</a> <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="group__stxetx.html#ga5">stxetxGetRxPacketDatalength</a>(<span class="keywordtype">void</span>)
00207 {
00208     <span class="comment">// return the packet's datalength</span>
00209     <span class="comment">// (subtract 1 from the offset because the STX has already been discarded)</span>
00210     <span class="keywordflow">return</span> stxetxRxPacket[STXETX_LENGTHOFFSET-1];
00211 }
00212 
<a name="l00213"></a><a class="code" href="group__stxetx.html#ga6">00213</a> <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span>* <a class="code" href="group__stxetx.html#ga6">stxetxGetRxPacketData</a>(<span class="keywordtype">void</span>)
00214 {
00215     <span class="comment">// return a pointer to the packet's data payload</span>
00216     <span class="comment">// (subtract 1 from the offset because the STX has already been discarded)</span>
00217     <span class="keywordflow">return</span> stxetxRxPacket+STXETX_DATAOFFSET-1;
00218 }
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