Help with basic arithmethic

I’m hoping that typing out a question will help me to figure out what I’m doing wrong in my sums, but I might be clicking “Create topic” if I don’t get anywhere, rubber ducking.

Basically I’m trying to send a MIDI tick message out on the MIDI Out connector. The MIDI tick status message 0xF8, is transmitted 24 times per quarter note. Now for the maths:

  • ModDwarf reports a sample rate of 48,000 which is samples per second I assume, (A Frequency)
  • I’m trying to get 80 BPM which would be 80/60 Beats per second = 1.33333
  • So I’d be expecting 48K * 1.3333 samples per beat (63,998.4)
  • So if I want 24 ticks per beat I want 63,998.4 / 24) = 2,666.6 samples per MIDI Tick

So now my code, all those numbers check out, in my head anyhow. So my instance data keeps a count variable which is a float. I’ve also got a local_count in my run() method. All I do is:

local_count = self->count + n_samples;    // n_samples is the number of samples sent to run() 128
if (local_count > 2,666.6) {
    self->count = local_count - 2,666.6;
} else {
    self->count = local_count;

All that looks right to me but the synth connected to the ModDwarf is reporting a BPM of 45. Sooo far out.

It occurred to me overnight I should be dividing not multiplying :frowning:

Sorted it