This is exactly the same behavior seen in the Arduino's PWM functionality. Additionally, the use of hardware timers allows for tones to be generated continuously, regardless of other events occurring. By using timers instead of solely software-based toggling, the system is able to eliminate delays caused by processes not directly related to toggling of the pins, such as iterating counters in for-loops. However, instead of simply toggling the selected pin high and low, the algorithm uses internal timer pre-scalers to achieve a higher precision frequency, and thus closer pitch. The process above is the basic algorithm that the built-in Arduino tone() function performs. From there, hold the signal high for 1.13636 milliseconds, and low for the same amount of time. So in order to produce an A4 note, one would find the period of that note, 1/440 = 2.2727 milliseconds.

Once that value is known, it's a simple matter of keeping the signal high for half the length of the period, and low for the other half. This is done by taking the inverse of the frequency (Period=1/Frequency). In order to generate a specific frequency, the period of the note needs to be found, which is the amount of time it takes for the signal to cycle once. The simplest approach is to generate a 50% duty cycle pulse stream and set the frequency to the desired pitch. In order to produce a variety of pitches, a digital signal needs to convey the frequency of sound it is trying to reproduce. So, to find the frequency of A6 from A4 (440Hz) calculate 440Hz To find the frequency of a note in any other octave, take the frequency of the current octave and multiply it by 2^n, where n is the number of octaves up or down. The next octave, A3, is double of A2, or 220Hz. For example, 55Hz is called A1, and 110Hz is A2.

In music, specific frequencies of sound have been named, and doubling of these fundamental frequencies results in the same notes in higher octaves. The pitch of a sound may be its true frequency, or may be a result of overtones which are perceived as a particular pitch. PWM can be applied to make sounds with a speaker, but the frequency needs to be modified to generate various tones.Д®very sound humans encounter consists of one or more frequencies, and the way the ear interprets those sounds is called pitch. The number of applications PWM works with is vast and includes servo motor positioning, DC motor speed control, LED brightness, and sound effects. By varying the duty cycle, or the ratio of time the signal is high to low, a digital system is able to continuously vary the output of a given system while maintaining a constant frequency (Arduino PWM pins produce signals at 490Hz or at 980Hz). With this technique, the amount of power a system receives depends on the duty cycle of the PWM signal. Pulse width modulation (PWM) is a familiar method for simulating analog signals using digital outputs. Computer systems often need to interface with devices that have analog outputs.

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