Slacker's midi clock metronome PLUS tap trigger (AKA TikTakTap)

[CarpathiART]

Hi,

Thanks for the quick response. I didin´t come to think of it. I shall put this thing into testing.

K

[slacker]

Yeah that should work, the tap tempo output is a 5 volt pulse at the BPM/quarter note set by the MIDI clock. If you wanted to output the actual MIDI clock which is 24 pulses per quarter note the code would need modifying.

[acobberson]

Hey guys, is anyone offering pre-flashed chips for this project? I'd be a buyer I'd there was a seller 

[ElectricDruid]

One question: most MIDI devices use an optical isolator on MIDI IN, and sometimes a 74LS14 to sharpen up the incoming waveform. Any reason why at least the isolator was not used here?

No opto isolator was used because this was designed to be powered by the MIDI device that it's connected to, if you add an isolator you can't do this and would need to add a power supply. If you use it just as a metronome then it has no connections to any other device so there's nothing to isolate it from and the relay isolates the taptempo output.
If you need to power it or you build it into a pedal then yes to make it comply with the MIDI standard you should add an opto isolator.

Oooh, you dirty boy...

This "MIDI-powered device" is a neat trick when it works, but it doesn't always. I'm guessing you know that, Slacker, so really I'm just waving a warning flag for other people who might think this is a great idea. Think about what happens if I'm running a MIDI out from a processor at 3.3V. Fully MIDI standard compatible (since MIDI is a *current* based standard) but screws up any gadget that expects to see 5V. There is no MIDI voltage standard. You can't rely on getting a certain supply from a MIDI output - it's not a bleeding USB Port!! If you're building kit you use in your particular set-up, then fine, do it. But don't expect it to work everywhere in every situation, because it won't.

Ok, warning over. As you were.

HTH,
Tom

[lars-musik]

Hi Tom, the layout I posted above runs on 9V with an 78L05 regulator. That should keep the troubles in check, right?

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[ElectricDruid]

Yes, absolutely. Run it off its own 5V supply and stick the optocoupler on it to avoid ground loops (that's why MIDI always has an opto) and you'll be standard-compliant and it should work with everything else that is.

Tom