Reading Switches with ATtiny2313

Step 5 Using Timer/Counter 0 for Beeps

The ATtiny2313 has two powerful timer/counter resources: one 8-bit and one 16-bit. These may be configured as frequency generators, variable pulse width modulation controllers, and output compare registers. The full functionality of these is described in 49 pages of the data sheet. However, we'll use a simple case. Only Timer/Counter 0 (the 8-bit one) will be used and it will be used simply as a frequency generator. The frequency will be routed to a small speaker to produce a beep. Timer/Counter 0 is fully described in pages 66 to 83 of the ATtiny2313 data sheet. A close reading of this material will provide one with a complete understanding of Time/Counter 0. Happily, a fairly simple mode, Clear Timer on Compare (CTC), is all that is required to generate the beep tone we want.

For the mode we'll use, operation of the Timer/Counter is straight-forward. When a clock signal is selected, the counter starts at zero and increments each clock pulse. When the counter value reaches the value in the Output Compare Register (TOP), the counter resets to zero and counting starts again. The output bit associated with the Timer/Counter is toggled to produce a square wave output. This directly drives an audio transducer to make a beep sound.

A small TDK Audio Transducer produces the beep. A suitable unit is Digikey 445-2530-ND, TDK SD1209T3-A1 (I used an early version of this). This is a 3 volt version; the 5 volt version will also work I expect. I drive this directly off the output port of the Attiny2313 and it seems to work fine. Sparkfun has a similar device.