Getting Started

Chapter 8: C Pointers and Arrays

/ 2 = 1911

imer1 to generate a phase/frequency

We then compensate for our

sing a left bit shift of one

eft shifting a byte or integer doubles

is less than half the possible

lue, 256/2 for a byte.)

ew tones from the sound.h table:

// tone 2

time we play the tone. The Timer0 calls

at 10ms intervals. It begins by getting the tempo from the

ay and putting it into a Tempo variable. The next time

d, if Tempo is not 0, it decrements the tempo and exits. It

the Tempo is 0, when it rereads the tempo and starts

Tone = 220*2^(NOTE/12)

When NOTE = C0 we get:

Tone = 220*2^(3/12) = 261.6256.

We get the frequency to generate for the tone with:

Timer value = 1Mhz / Tone / 2

For the C0 we would have:

Timer value = 1000000 / 261,6256...

So when we want to generate a C0 we set T
correct PWM with a top value calculated as above.
using a 2Mhz cpu clock by doubling the value u
position. (In case you didn’t get this earlier, l
it if there is headroom. Headroom means the value
va

A f

#define a 2273 // tone 0

#define xa 2145 // tone 1

#define ax 2145 // tone 1

#define b 2024

#define c0 1911 // tone 3

Setting the tempo

The tempo, in this case, is the length of
the Play_Tune function
first position of the arr
Play_Tune is calle
continues to do this until
over.