TA的每日心情 | 郁闷
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签到天数: 1647 天 连续签到: 4 天 [LV.Master]伴坛终老
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《韩非子·内储说上》中有一段寓言：“齐宣王使人吹竽，必三百人。南郭处士请为王吹竽，宣王悦之，廪食以数百人。宣王死，湣王立，好一一听之，处士逃。”用今天的话说就是齐宣王让人吹竽，一定要三百人一起吹。南郭处士请求为齐宣王吹竽，宣王很高兴。官仓供养的乐手有好几百人。齐宣王死后，他的儿子湣王继位。湣王也喜欢听吹竽，但他喜欢让他们一个一个地吹，南郭处士只好逃走了。今天提起这个故事，一是要喷一喷PWM，二则是五音不全的楼主秀一下音乐羞痒（脸皮之厚，南郭弗如。呵呵）。
PWM大家都知道，输出占空比的。频率很低的时候可以用来闪LED，频率高了的话就不只是调LED亮度了，可以当作模拟输出，记得有个用法是提供LCD偏压，算是低调奢华有内涵的方式。今天博主分享的，是比较土憋矫情无下限的用法——驱动蜂鸣器奏乐。
在神奇的wiki 上，可以查到这个表格，记载了各个音高的对应频率：
频率,单位为赫兹 (括号内为半音距离,"(0)"为中央C) | 八度 →
音名 ↓ | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | C | 16.352 (−48) | 32.703 (−36) | 65.406 (−24) | 130.81 (−12) | 261.63 (0) | 523.25 (+12) | 1046.5 (+24) | 2093.0 (+36) | 4186.0 (+48) | 8372.0 (+60) | C♯/D♭ | 17.324 (−47) | 34.648 (−35) | 69.296 (−23) | 138.59 (−11) | 277.18 (+1) | 554.37 (+13) | 1108.7 (+25) | 2217.5 (+37) | 4434.9 (+49) | 8869.8 (+61) | D | 18.354 (−46) | 36.708 (−34) | 73.416 (−22) | 146.83 (−10) | 293.66 (+2) | 587.33 (+14) | 1174.7 (+26) | 2349.3 (+38) | 4698.6 (+50) | 9397.3 (+62) | D♯/E♭ | 19.445 (−45) | 38.891 (−33) | 77.782 (−21) | 155.56 (−9) | 311.13 (+3) | 622.25 (+15) | 1244.5 (+27) | 2489.0 (+39) | 4978.0 (+51) | 9956.1 (+63) | E | 20.602 (−44) | 41.203 (−32) | 82.407 (−20) | 164.81 (−8) | 329.63 (+4) | 659.26 (+16) | 1318.5 (+28) | 2637.0 (+40) | 5274.0 (+52) | 10548 (+64) | F | 21.827 (−43) | 43.654 (−31) | 87.307 (−19) | 174.61 (−7) | 349.23 (+5) | 698.46 (+17) | 1396.9 (+29) | 2793.8 (+41) | 5587.7 (+53) | 11175 (+65) | F♯/G♭ | 23.125 (−42) | 46.249 (−30) | 92.499 (−18) | 185.00 (−6) | 369.99 (+6) | 739.99 (+18) | 1480.0 (+30) | 2960.0 (+42) | 5919.9 (+54) | 11840 (+66) | G | 24.500 (−41) | 48.999 (−29) | 97.999 (−17) | 196.00 (−5) | 392.00 (+7) | 783.99 (+19) | 1568.0 (+31) | 3136.0 (+43) | 6271.9 (+55) | 12544 (+67) | G♯/A♭ | 25.957 (−40) | 51.913 (−28) | 103.83 (−16) | 207.65 (−4) | 415.30 (+8) | 830.61 (+20) | 1661.2 (+32) | 3322.4 (+44) | 6644.9 (+56) | 13290 (+68) | A | 27.500 (−39) | 55.000 (−27) | 110.00 (−15) | 220.00 (−3) | 440.00 (+9) | 880.00 (+21) | 1760.0 (+33) | 3520.0 (+45) | 7040.0 (+57) | 14080 (+69) | A♯/B♭ | 29.135 (−38) | 58.270 (−26) | 116.54 (−14) | 233.08 (−2) | 466.16 (+10) | 932.33 (+22) | 1864.7 (+34) | 3729.3 (+46) | 7458.6 (+58) | 14917 (+70) | B | 30.868 (−37) | 61.735 (−25) | 123.47 (−13) | 246.94 (−1) | 493.88 (+11) | 987.77 (+23) | 1975.5 (+35) | 3951.1 (+47) | 7902.1 (+59) | 15804 (+71)
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由于这次只用中音1234567，所以我们只关注八度为4的CDEFGAB,取其倒数，乘1000000取整，就变成了3822 ,3405 ,3034 ,2863 ,2551 ,2273 ,2025，这就是每秒震动次数，然后以此为基础，设置CompareValue为其1/2即可。
组件很简单，因为没有用连续的Pin所以输入定义了6个：
引脚这样分配的：
实物接线更简单：
下面是代码：- #include <device.h>
-
- void main()
- {
- Clock_1_Start();
- PWM_1_Start();
- for(;;)
- {
- if(!Pin_Button_1_Read()){
- Pin_LED_Write(0);
- PWM_1_WritePeriod(3822);
- PWM_1_WriteCompare1(3822>>1);
- }else if(!Pin_Button_2_Read()){
- Pin_LED_Write(0);
- PWM_1_WritePeriod(3405);
- PWM_1_WriteCompare1(3405>>1);
- }else if(!Pin_Button_3_Read()){
- Pin_LED_Write(0);
- PWM_1_WritePeriod(3034);
- PWM_1_WriteCompare1(3034>>1);
- }else if(!Pin_Button_4_Read()){
- Pin_LED_Write(0);
- PWM_1_WritePeriod(2863);
- PWM_1_WriteCompare1(2863>>1);
- }else if(!Pin_Button_5_Read()){
- Pin_LED_Write(0);
- PWM_1_WritePeriod(2551);
- PWM_1_WriteCompare1(2551>>1);
- }else if(!Pin_Button_6_Read()){
- Pin_LED_Write(0);
- PWM_1_WritePeriod(2273);
- PWM_1_WriteCompare1(2273>>1);
- }else if(!Pin_Button_7_Read()){
- Pin_LED_Write(0);
- PWM_1_WritePeriod(2025);
- PWM_1_WriteCompare1(2025>>1);
- }else{
- Pin_LED_Write(1);
- PWM_1_WritePeriod(9999);
- PWM_1_WriteCompare1(0);
- }
- }
- }
12345-20131028184816.rar
(1.22 MB, 下载次数: 22)
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发表于 2013-11-29 17:39:56
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