How to generate sound using PWM with PIC microcontroller?
Generating an audible sine wave and producing its sound in a Loud Speaker is the first step towards using the microcontroller in audio applications like media player, announcement system, record and playback etc. The PIC18F4550 has four PWM output channels and they are P1A, P1B, P1C and P1D.
How is PWM used in a filter circuit?
The P1A is the PWM channel in this particular project. This channel is used to generate the PWM waves which are then applied to a filter circuit to generate the sine wave which is described in a previous project on PIC Sine Wave Generation.
How does Pulse Width Modulation ( PWM ) work?
Pulse Width Modulation (PWM) is a technique in which the width of a pulse is modulated keeping the time period of the wave constant. The ON time and OFF time can have any different values in the wave cycles, but the sum of the ON time and OFF time remains same for the entire cycles.
How is a sine wave generated in PWM?
In this particular project the sine wave samples are generated periodically by re-writing the value of the CCPR1 register to vary the Duty-cycle. It is done by generating interrupts periodically with another timer module timer0 and changing the CCPR1 value when the code is inside the timer0’s ISR.
Can a PWM be used to generate a voltage?
PWM is a digital wave that can be generated using digital circuits which are not capable of generating analog voltages. With the help of the modulation of the width of a pulse in a period of the wave, they can generate any required voltage with the help of a proper filter circuits.
How to generate a tone with PWM signal?
Typically a push-pull is used as actively driving both high and low results in better speaker response. It also allows for a series capacitor, acting as a simple high-pass filter to protect the speaker from long DC periods. This, for example, should work: http://3.bp.blogspot.com/-FFBftqQ0o8c/Tb3x2ouLV1I/AAAAAAAABIA/FFmW9Xdwzec/s400/sound.png
Is there a way to filter PWM signal?
Filtering it well in analogue circuitry without affecting the sound that you want to hear may not be a very easy thing to do (sharp LPF filters are tricky/expensive, cheap filters are poor).