pulse_8c-source.html

avr cpu 库源代码 对avr单片机编程很有帮助

00142 
00143 <span class="keywordtype">void</span> pulseT1BRun(u16 nPulses)
00144 {
00145     <span class="comment">// set the number of pulses we want and the mode</span>
00146     <span class="keywordflow">if</span>(nPulses)
00147     {
00148         <span class="comment">// if the nPulses is non-zero, use "counted" mode</span>
00149         PulseT1BMode |= PULSE_MODE_COUNTED;
00150         PulseT1BCount = nPulses&lt;&lt;1;
00151     }
00152     <span class="keywordflow">else</span>
00153     {
00154         <span class="comment">// if nPulses is zero, run forever</span>
00155         PulseT1BMode &amp;= ~PULSE_MODE_COUNTED;
00156         PulseT1BCount = 1&lt;&lt;1;
00157     }
00158     <span class="comment">// set OutputCompare action to toggle OC1B pin</span>
00159     <span class="comment">// (note: with all the A's and B's flying around, TCCR1A is not a bug)</span>
00160     cbi(TCCR1A,COM1B1);
00161     sbi(TCCR1A,COM1B0);
00162 
00163     <span class="comment">// now the "enabling" stuff</span>
00164 
00165     <span class="comment">// set the output compare one pulse cycle ahead of current timer position </span>
00166     <span class="comment">// to make sure we don't have to wait until the timer overflows and comes</span>
00167     <span class="comment">// back to the current value</span>
00168     <span class="comment">// set future output compare time to TCNT1 + PulseT1APeriodTics</span>
00169     <span class="comment">//outw(OCR1B, inw(TCNT1) + PulseT1BPeriodTics);</span>
00170     OCR1B += PulseT1BPeriodTics;
00171 
00172     <span class="comment">// enable OutputCompare interrupt</span>
00173     sbi(TIMSK, OCIE1B);
00174 }
00175 
00176 <span class="keywordtype">void</span> pulseT1AStop(<span class="keywordtype">void</span>)
00177 {
00178     <span class="comment">// stop output regardless of remaining pulses or mode</span>
00179     <span class="comment">// go to "counted" mode</span>
00180     PulseT1AMode |= PULSE_MODE_COUNTED;
00181     <span class="comment">// set pulses to zero</span>
00182     PulseT1ACount = 0;
00183 }
00184 
00185 <span class="keywordtype">void</span> pulseT1BStop(<span class="keywordtype">void</span>)
00186 {
00187     <span class="comment">// stop output regardless of remaining pulses or mode</span>
00188     <span class="comment">// go to "counted" mode</span>
00189     PulseT1BMode |= PULSE_MODE_COUNTED;
00190     <span class="comment">// set pulses to zero</span>
00191     PulseT1BCount = 0;
00192 }
00193 
00194 u16 pulseT1ARemaining(<span class="keywordtype">void</span>)
00195 {
00196     <span class="comment">// return the number of pulses remaining for channel A</span>
00197     <span class="comment">// add 1 to make sure we round up, &gt;&gt;1 equivalent to /2</span>
00198     <span class="keywordflow">return</span> (PulseT1ACount+1)&gt;&gt;1;
00199 }
00200 
00201 u16 pulseT1BRemaining(<span class="keywordtype">void</span>)
00202 {
00203     <span class="comment">// return the number of pulses remaining for channel A</span>
00204     <span class="comment">// add 1 to make sure we round up, &gt;&gt;1 equivalent to /2</span>
00205     <span class="keywordflow">return</span> (PulseT1BCount+1)&gt;&gt;1;
00206 }
00207 
00208 <span class="keywordtype">void</span> pulseT1AService(<span class="keywordtype">void</span>)
00209 {
00210     <span class="comment">// check if TimerPulseACount is non-zero</span>
00211     <span class="comment">//      (i.e. pulses are still requested)</span>
00212     <span class="keywordflow">if</span>(PulseT1ACount)
00213     {
00214         <span class="comment">//u16 OCValue;</span>
00215         <span class="comment">// read in current value of output compare register OCR1A</span>
00216         <span class="comment">//OCValue =  inp(OCR1AL);       // read low byte of OCR1A</span>
00217         <span class="comment">//OCValue += inp(OCR1AH)&lt;&lt;8;    // read high byte of OCR1A</span>
00218         <span class="comment">// increment OCR1A value by PulseT1APeriodTics</span>
00219         <span class="comment">//OCValue += PulseT1APeriodTics;</span>
00220         <span class="comment">// set future output compare time to this new value</span>
00221         <span class="comment">//outp((OCValue&gt;&gt;8),        OCR1AH);    // write high byte</span>
00222         <span class="comment">//outp((OCValue &amp; 0x00FF),OCR1AL);  // write low byte</span>
00223 
00224         <span class="comment">// the following line should be identical in operation</span>
00225         <span class="comment">// to the lines above, but for the moment, I'm not convinced</span>
00226         <span class="comment">// this method is bug-free.  At least it's simpler!</span>
00227         <span class="comment">//outw(OCR1A, inw(OCR1A) + PulseT1APeriodTics);</span>
00228         <span class="comment">// change again</span>
00229         OCR1A += PulseT1APeriodTics;
00230                         
00231         <span class="comment">// decrement the number of pulses executed</span>
00232         <span class="keywordflow">if</span>(PulseT1AMode &amp; PULSE_MODE_COUNTED)
00233             PulseT1ACount--;
00234     }
00235     <span class="keywordflow">else</span>
00236     {
00237         <span class="comment">// pulse count has reached zero</span>
00238         <span class="comment">// disable the output compare's action on OC1A pin</span>
00239         cbi(TCCR1A,COM1A1);
00240         cbi(TCCR1A,COM1A0);
00241         <span class="comment">// and disable the output compare's interrupt to stop pulsing</span>
00242         cbi(TIMSK, OCIE1A);
00243     }
00244 }
00245 
00246 <span class="keywordtype">void</span> pulseT1BService(<span class="keywordtype">void</span>)
00247 {
00248     <span class="comment">// check if TimerPulseACount is non-zero</span>
00249     <span class="comment">//      (i.e. pulses are still requested)</span>
00250     <span class="keywordflow">if</span>(PulseT1BCount)
00251     {
00252         <span class="comment">//u16 OCValue;</span>
00253         <span class="comment">// read in current value of output compare register OCR1B</span>
00254         <span class="comment">//OCValue =  inp(OCR1BL);       // read low byte of OCR1B</span>
00255         <span class="comment">//OCValue += inp(OCR1BH)&lt;&lt;8;    // read high byte of OCR1B</span>
00256         <span class="comment">// increment OCR1B value by PulseT1BPeriodTics</span>
00257         <span class="comment">//OCValue += PulseT1BPeriodTics; </span>
00258         <span class="comment">// set future output compare time to this new value</span>
00259         <span class="comment">//outp((OCValue&gt;&gt;8),        OCR1BH);    // write high byte</span>
00260         <span class="comment">//outp((OCValue &amp; 0x00FF),OCR1BL);  // write low byte</span>
00261 
00262         <span class="comment">// the following line should be identical in operation</span>
00263         <span class="comment">// to the lines above, but for the moment, I'm not convinced</span>
00264         <span class="comment">// this method is bug-free.  At least it's simpler!</span>
00265         <span class="comment">//outw(OCR1B, inw(OCR1B) + PulseT1BPeriodTics);</span>
00266         <span class="comment">// change again</span>
00267         OCR1B += PulseT1BPeriodTics;
00268 
00269         
00270         <span class="comment">// decrement the number of pulses executed</span>
00271         <span class="keywordflow">if</span>(PulseT1BMode &amp; PULSE_MODE_COUNTED)
00272             PulseT1BCount--;
00273     }
00274     <span class="keywordflow">else</span>
00275     {
00276         <span class="comment">// pulse count has reached zero</span>
00277         <span class="comment">// disable the output compare's action on OC1B pin</span>
00278         cbi(TCCR1A,COM1B1);
00279         cbi(TCCR1A,COM1B0);
00280         <span class="comment">// and disable the output compare's interrupt to stop pulsing</span>
00281         cbi(TIMSK, OCIE1B);
00282     }
00283 }
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