Building the Mini YM synth MIDI shiled

I’m going to build the MIDI shield for the Mini YM Synth following these schematics (attached below), but I need a little help, tell me if this BOM is correct please, I don’t want to waste time and money (albeit components being cheap):

1x MIDI female plug
Resistors: 220 x2, 2.2K x1
Caps: 1uF ceramic and 10uF electrolitic
1x 1N914 diode (is this the diode?)
1x CNY17-1 optocoupler
1x three pin header
1x L7805 voltage regulator
1x led
1x SPST switch

is this everything?

ehm… have to bug you with another question:
I’m not sure I’m reading the schematics correctly, is there a connection in the places I’ve marked with an arrow? I suppose not, but to be sure…
question2: is the red marked square the optocoupler? Why don’t I see 6 legs there?

UPDATE: uploaded correct picture

I don’t see the annotations. U1 is an optocoupler, it has a non-connected (useless) leg.

ehm sorry, I uploadad the wrong picture… I’ve corrected it now.
Anyway thanks, the useless leg was confusing me.

There is no connection at the arrow on the left (otherwise you’re shorting the device sending the MIDI data, though it must have a protection resistor to be protected against that).

The thing in the box is the optocoupler. An optocoupler is really a LED on one side and a phototransistor on the other side, sealed together.

There is a connection at the arrow on the right - C1 and C2 are smoothing caps for the power supply and must be tied to ground.

thanks a lot for the detailed instructions! just one last question: is there a connection at the arrow right next to the optocoupler?


ok, now I know it all! Thanks again!

going to build the same thing for the MIDIo. the parts arrived yesterday, but my neighbors took it because i was not at home and today they were not at home :frowning:

please report, if it worked that way. are you going to put an resistor for R1?
Mat said it should work without it.

i was wondering about the connectin next to the optocoupler, too. thanks pichenettes, for helping out with that.

Well I’m going to breadboard it before I build it… so I can check and see if R1 is needed or not.
I’ll keep you posted!

I was trying to reupload the schematics since they got corrupted during the server migration, but I won’t let me…

Upload fixed

thanks a lot!

Ok, I have reuploaded the schematics. I don’t have the one with my annotations anymore, so that one is still broken (but not a great deal I think).

Awesome. Will use your circuit to make a little box with 2 x YM minis that will be midified.
Many thanks for sharing this info.

Regarding integrating this MIDI circuit with the ym mini, I assume you need to connect the
J1 pins to the YM mini board.

Which pins to use (read the YM docs and I am prob senile because I could not find this info)?

@deebeecee: you’re welcome, though It’s not my circuit, credit goes to Wil Lindsay, the guy who made the Mini YM Synth.
Anyway, yes J1 is the FTDI header on the Mini YM, so you connect the Midi Shield there (instead of the usb cable). I will also get powered by it of course.

ok I tried to build the thing. but utterly failed! :slight_smile:
the YM powers on, but when I send some midi nothing happens. Checked the midi cable, checked the audio cable, double checked the schematics orientation of components, but nothing, seems to be all right.

Well there are two things that might not be 100% as in the BOM I listed above. I bought a bunch of wrong caps, 1nF electrolytic instead of ceramic, does that make a difference in this case?
problem nr.2 I bought the wrong resistors, the huge green one is a metallic resistor… but again, value is the same, so it shouldn’t be a problem, or is it?

I’m pretty sure I soldered the cables to the midi connector correctly nr.5 is the second from left and nr.4 is the 4th, right?

I don’t know what else could be wrong… so I’m attaching some photos of my breadboard (sorry Olivier for using this forum for non-shruthi related things, but the forums over at Wil’s site are totally dead and here I get lots of people with experience from which I can learn things)

so here comes photo nr.1


and one that shows how the cables are attached on the FTDI header

I spoke with Wil last week about PCBs for this. He didn’t think people would be interested. I assured him he’d have no problem selling a few to some of the mutable gang and this post looks like proof!

I feel your pain rumplefilter. This is the exact reason I didn’t even bothertrying this myself. I’m pretty got at soldering kits, not so much at assembling a circuit from schematic. I’ll forward this thread to Wil as ammo for a batch of PCBs!

Hmm, from the pictures you seem to have built it right as far as I can tell.
Regarding the component choice, electrolytic caps are fine and the type of resistor does not matter here if the values are OK.
One thing I though of, I think the listed capacitors may be a bit small if the mini-YM-thingie draws a bit of current and if your power source is not well stabilized from the start (like for example a 9V battery) - compare the Shruthi filter board schematics, there 100uF and 220uF caps are used in the same place.

For the MIDI pinout, see for example here:
For troubleshooting you should be able to just swap the green cables to test if pin 4 and 5 are mixed up.

Good luck! =)

i have the parts laying around, too. but had no time to build it yet.

maybe you could compare with this schematic, which does a similar thing and is proofed to be working;

i would be interested in PCB aswell.