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62 lines
1.9 KiB
C++
62 lines
1.9 KiB
C++
/*
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*
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* Simple (PWM) Oscillator Explained
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*
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Instead of using the Tone() function, you can create a square wave oscillator by
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turning the digital pin 11 (speakerpin) on (HIGH) and off (LOW) very fast:
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HIGH | ___ ___
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| | | | | 50% duty cycle
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LOW | ____| |____| | (50% on, 50 off) Determined by delayMicroseconds()
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|____________________
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TIME
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*
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*
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*
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*
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*
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*/
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#define SPEAKER_PIN 11
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void setup() {
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// set pin 11 as output
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pinMode(SPEAKER_PIN, OUTPUT);
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}
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void loop() {
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//in simple-osc.ino we use tone(outputpin, 1000); to make a 1000Hz tone
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//1000Hz means 1000x on and off in one second.
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//instead of using tone(), we can write out what happens:
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//turn on a pin on and of on/off 1000x per second:
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digitalWrite( SPEAKER_PIN, LOW ); //turn pin off
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delayMicroseconds( 500 ); // wait
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digitalWrite( SPEAKER_PIN, HIGH );//tunr pin on
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delayMicroseconds( 500 ); // wait
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//the wait period determains how long it takes to loop through the
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//code, and thus how fast the code runs, and thus how fast
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//the pin turns on and off and thus at what frequency this happens:
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//we get an oscillation (on-off)!
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//Maths:
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// for 1Hz, the pin goes on and off in one second. So the delay should be 0.5 second
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// for 1000Hz the pin goes on/off 1000x in 1 sec. So the delay should be 1000x smaller: 0.0005 seconds
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// wich is 500 micro seconds (dont confuse milliseconds with microseconds).
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//To control the frequency with a knob we can use analogRead, uncomment the code below (and comment out the one above):
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// digitalWrite( SPEAKER_PIN, LOW ); //turn pin off
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// delayMicroseconds( analogRead(A2) ); // wait
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// digitalWrite( SPEAKER_PIN, HIGH );//tunr pin on
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// delayMicroseconds( analogRead(A2) ); // wait
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}
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