![]() ![]() ![]() To use it with an 8MHz clock add 3 to the prescaler, to reduce the frequency by an additional factor of 8, as shown in the commented second line of the routine. We will define a constant for each divisor to save having to remember them for example C is: const int Note_C = 239 The solution is to set the prescaler to divide the clock by 2^4, or 16. However, the divider for the counter must fit into 8 bits, so the maximum number we can represent is 255. To calculate the divisor for a given note frequency we first work out:įor example, C4 (middle C) is 261.63Hz, so we get: We then just need a table of divisors for the notes within one octave. So TinyTone() is written to take three parameters the note divisor, the octave number, and the duration in milliseconds : TinyTone(divisor, octave, duration) The square wave is output on digital output 1.īecause the prescaler divides the clock by a power of two it provides a convenient way of generating the octave. This divides the clock frequency, which is either 1MHz or 8MHz, by a prescaler, and then by a one-byte counter. The first of these is already used by the delay() function, so I've used Timer/Counter1. The ATtiny85 contains two timers, referred to as Timer/Counter0 and Timer/Counter1. To test this application I used SparkFun's Tiny AVR Programmer (available in the UK from Proto-PIC ), which lets you program the ATtiny45 or ATtiny85 using the Arduino development environment. This post describes my simple TinyTone() function which takes advantage of the ATtiny85's prescaler to provide a compact tone routine that only needs a table of 12 divisors. There are several existing tone libraries for the ATtiny85, but they all seemed overcomplicated for what I wanted. I therefore needed to find a replacement way of generating simple tones. For a recent project based on the ATtiny85 I wanted to play some simple tones through a piezoelectric speaker, but unfortunately the Arduino tone() function isn't supported on the ATtiny85 because it doesn't have the appropriate timers. ![]()
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