2
I tried the code on an Uno and as you say, it does sound odd.
By my calculations, the frequency is 40kHz (16MHz/(200 x 2)), which is above the threshold of hearing. The sound we are actually hearing is probably the 3rd or 5th harmonic, at a reduced intensity and perhaps subject to jitter.
I tried changing
TCCR2B = _BV(CS20); // clk/1
to
TCCR2B = _BV(...
1
Looks like my tone frequency was possibly just too high for the buzzer I was using, causing strange output.
Adjusting the clock divider fixed the issue. That is, I changed the following:
TCCR2B = _BV(CS20); // clk/1
to
TCCR2B = _BV(CS22) | _BV(CS20); // clk/128
and now I get reasonable-sounding tones.
Note that the clock divider you choose is ...
1
This:
led* redLed;
defines a global variable implicitly initialized to zero (i.e. a NULL
pointer). This is an invalid pointer you are not allowed to use until
you properly initialize it.
Here:
redLed->pin = 3;
you are writing to the memory pointed to by this invalid pointer. This
invokes what the C and C++ standards call undefined behavior. What
that ...
1
This is just a partial, rushed answer.
You should be able to get a significant speed-up if you define your own
ISR for handling the interrupt, as in:
ISR(INT1_vect) { ... }
The Arduino way of using interrupts is instead
void trigger() { ...}
void setup() {
attachInterrupt(int_number, trigger, CHANGE);
...
}
but this is slow, as it involves the ...
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