uartsw_8c-source.html

ATMEL的AVR单片机库文件

00178             UartswTxData = UartswTxData>>1;
00179         }
00180         <span class="keywordflow">else</span>
00181         {
00182             <span class="comment">// transmit stop bit</span>
00183             cbi(<a class="code" href="uartsw2conf_8h.html#a1">UARTSW_TX_PORT</a>, <a class="code" href="uartsw2conf_8h.html#a3">UARTSW_TX_PIN</a>);
00184         }
00185         <span class="comment">// schedule the next bit</span>
00186         outw(OCR1A, inw(OCR1A) + UartswBaudRateDiv);
00187         <span class="comment">// count down</span>
00188         UartswTxBitNum--;
00189     }
00190     <span class="keywordflow">else</span>
00191     {
00192         <span class="comment">// transmission is done</span>
00193         <span class="comment">// clear busy flag</span>
00194         UartswTxBusy = FALSE;
00195     }
00196 }
00197 
<a name="l00198"></a><a class="code" href="uartsw2_8h.html#a8">00198</a> <span class="keywordtype">void</span> <a class="code" href="uartsw_8c.html#a17">uartswRxBitService</a>(<span class="keywordtype">void</span>)
00199 {
00200     <span class="comment">// this function runs on either:</span>
00201     <span class="comment">// - a rising edge interrupt</span>
00202     <span class="comment">// - OC1B</span>
00203     <span class="keywordflow">if</span>(!UartswRxBusy)
00204     {
00205         <span class="comment">// this is a start bit</span>
00206         <span class="comment">// disable ICP interrupt</span>
00207         cbi(TIMSK, TICIE1);
00208         <span class="comment">// schedule data bit sampling 1.5 bit periods from now</span>
00209         outw(OCR1B, inw(TCNT1) + UartswBaudRateDiv + UartswBaudRateDiv/2);
00210         <span class="comment">// clear OC1B interrupt flag</span>
00211         sbi(TIFR, OCF1B);
00212         <span class="comment">// enable OC1B interrupt</span>
00213         sbi(TIMSK, OCIE1B);
00214         <span class="comment">// set start bit flag</span>
00215         UartswRxBusy = TRUE;
00216         <span class="comment">// reset bit counter</span>
00217         UartswRxBitNum = 0;
00218         <span class="comment">// reset data</span>
00219         UartswRxData = 0;
00220     }
00221     <span class="keywordflow">else</span>
00222     {
00223         <span class="comment">// start bit has already been received</span>
00224         <span class="comment">// we're in the data bits</span>
00225         
00226         <span class="comment">// shift data byte to make room for new bit</span>
00227         UartswRxData = UartswRxData&gt;&gt;1;
00228 
00229         <span class="comment">// sample the data line</span>
00230         <span class="keywordflow">if</span>( !(inb(<a class="code" href="uartsw2conf_8h.html#a6">UARTSW_RX_PORTIN</a>) &amp; (1&lt;&lt;<a class="code" href="uartsw2conf_8h.html#a7">UARTSW_RX_PIN</a>)) )
00231         {
00232             <span class="comment">// serial line is low</span>
00233             <span class="comment">// record '1' bit (data inverted)</span>
00234             UartswRxData |= 0x80;
00235         }
00236 
00237         <span class="comment">// increment bit counter</span>
00238         UartswRxBitNum++;
00239         <span class="comment">// schedule next bit sample</span>
00240         outw(OCR1B, inw(OCR1B) + UartswBaudRateDiv);
00241 
00242         <span class="comment">// check if we have a full byte</span>
00243         <span class="keywordflow">if</span>(UartswRxBitNum &gt;= 8)
00244         {
00245             <span class="comment">// save data in receive buffer</span>
00246             <a class="code" href="buffer_8h.html#a5">bufferAddToEnd</a>(&amp;uartswRxBuffer, UartswRxData);
00247             <span class="comment">// disable OC1B interrupt</span>
00248             cbi(TIMSK, OCIE1B);
00249             <span class="comment">// clear ICP interrupt flag</span>
00250             sbi(TIFR, ICF1);
00251             <span class="comment">// enable ICP interrupt</span>
00252             sbi(TIMSK, TICIE1);
00253             <span class="comment">// clear start bit flag</span>
00254             UartswRxBusy = FALSE;
00255         }
00256     }
00257 }
00258 
00259 <span class="comment">/*</span>
00260 <span class="comment">void uartswRxBitService(void)</span>
00261 <span class="comment">{</span>
00262 <span class="comment">    u16 thisBitTime;</span>
00263 <span class="comment">    u08 bitperiods;</span>
00264 <span class="comment">    u08 i;</span>
00265 <span class="comment"></span>
00266 <span class="comment">    // bit transition was detected</span>
00267 <span class="comment">    // record bit's edge time</span>
00268 <span class="comment">    thisBitTime = inw(ICR1);</span>
00269 <span class="comment"></span>
00270 <span class="comment">    cbi(PORTB, 0);</span>
00271 <span class="comment"></span>
00272 <span class="comment">    if(!UartswRxStartBit)</span>
00273 <span class="comment">    {</span>
00274 <span class="comment">        // this is a start bit</span>
00275 <span class="comment">        // switch to falling-edge trigger</span>
00276 <span class="comment">        cbi(TCCR1B, ICES1);</span>
00277 <span class="comment">        // record bit time</span>
00278 <span class="comment">        UartswRxBitTime = thisBitTime;</span>
00279 <span class="comment">        // set start bit flag</span>
00280 <span class="comment">        UartswRxStartBit = TRUE;</span>
00281 <span class="comment">        // reset bit counter</span>
00282 <span class="comment">        UartswRxBitNum = 0;</span>
00283 <span class="comment">        // reset data</span>
00284 <span class="comment">        UartswRxData = 0;</span>
00285 <span class="comment">    }</span>
00286 <span class="comment">    else</span>
00287 <span class="comment">    {</span>
00288 <span class="comment">        // start bit has already been received</span>
00289 <span class="comment">        // we're in the data bits</span>
00290 <span class="comment">        </span>
00291 <span class="comment">        // how many bit periods since last edge?</span>
00292 <span class="comment">        bitperiods = (thisBitTime - UartswRxBitTime + UartswBaudRateDiv/2)/UartswBaudRateDiv;</span>
00293 <span class="comment">        // set last edge time</span>
00294 <span class="comment">        UartswRxBitTime = thisBitTime;</span>
00295 <span class="comment"></span>
00296 <span class="comment">        if(bitperiods &gt; 10)</span>
00297 <span class="comment">        {</span>
00298 <span class="comment">            // switch to trigger on rising edge</span>
00299 <span class="comment">            sbi(TCCR1B, ICES1);</span>
00300 <span class="comment">            // clear start bit flag</span>
00301 <span class="comment">            UartswRxStartBit = FALSE;</span>
00302 <span class="comment">        }</span>
00303 <span class="comment">        else</span>
00304 <span class="comment">        {</span>
00305 <span class="comment"></span>
00306 <span class="comment"></span>
00307 <span class="comment">        if( inb(TCCR1B) &amp; (1&lt;&lt;ICES1) )</span>
00308 <span class="comment">        {</span>
00309 <span class="comment">            // just triggered on a rising edge</span>
00310 <span class="comment">            // previous bits were zero</span>
00311 <span class="comment">            // shift in the data (data bits are inverted)</span>
00312 <span class="comment">            for(i=0; i&lt;bitperiods; i++)</span>
00313 <span class="comment">            {</span>
00314 <span class="comment">                UartswRxData = UartswRxData&lt;&lt;1;</span>
00315 <span class="comment">                UartswRxData |= 0x01;</span>
00316 <span class="comment">            }</span>
00317 <span class="comment">            // switch to trigger on falling edge</span>
00318 <span class="comment">            cbi(TCCR1B, ICES1);</span>
00319 <span class="comment">        }</span>
00320 <span class="comment">        else</span>
00321 <span class="comment">        {</span>
00322 <span class="comment">            // just triggered on a falling edge</span>
00323 <span class="comment">            // previous bits were one</span>
00324 <span class="comment">            // shift in the data (data bits are inverted)</span>
00325 <span class="comment">            for(i=0; i&lt;bitperiods; i++)</span>
00326 <span class="comment">            {</span>
00327 <span class="comment">                UartswRxData = UartswRxData&lt;&lt;1;</span>
00328 <span class="comment">            }</span>
00329 <span class="comment">            // switch to trigger on rising edge</span>
00330 <span class="comment">            sbi(TCCR1B, ICES1);</span>
00331 <span class="comment">        }</span>
00332 <span class="comment">        </span>
00333 <span class="comment">        // increment bit counter</span>
00334 <span class="comment">        UartswRxBitNum += bitperiods;</span>
00335 <span class="comment">        </span>
00336 <span class="comment">        // check if we have a full byte + start bit</span>
00337 <span class="comment">        if(bitperiods &gt; 8)</span>
00338 <span class="comment">        {</span>
00339 <span class="comment">            // save data in receive buffer</span>
00340 <span class="comment">            bufferAddToEnd(&amp;uartswRxBuffer, UartswRxData);</span>
00341 <span class="comment">            // switch to trigger on rising edge</span>
00342 <span class="comment">            sbi(TCCR1B, ICES1);</span>
00343 <span class="comment">            // clear start bit flag</span>
00344 <span class="comment">            UartswRxStartBit = FALSE;</span>
00345 <span class="comment">        }</span>
00346 <span class="comment">        }</span>
00347 <span class="comment">    }</span>
00348 <span class="comment"></span>
00349 <span class="comment">    // turn off debug LEDs</span>
00350 <span class="comment">    delay(10);</span>
00351 <span class="comment">    sbi(PORTB, 0);</span>
00352 <span class="comment">    sbi(PORTB, 1);</span>
00353 <span class="comment">}</span>
00354 <span class="comment">*/</span>
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