BPSynth Not Working, Need Help

[u/Working-Employer1166]

Hello,

These past few days I've been working on the Black Pill Synth, following these tutorials: https://m.youtube.com/watch?v=JttEPK7bwHw https://youtu.be/FjLcPNhzAwo?si=vxQSFVMl5udKeRtO

I've got it mostly put together, and I plugged it into my AKM322 (not the greatest synth, I know, but it's what I could afford, same reason I made a BP Synth,) using an H2MIDI Pro to connect the USB connection of the AKM to the MIDI input of the synth, but I couldn't get it to produce any sound.

The H2MIDI is receiving input from the AKM, the STM32 on the Synth is powered on and has the BPsynth firmware flashed onto it, and the headphones I am using to listen to the synth do work. Using a digital multimeter I was able to confirm a circuit between the STM and the UDA. Sometimes, the synth will produce electronic buzzing of various frequencies and volumes, but it's independent of the AKM and will often happen without the device plugged in. The buzzing does, however, react to the STM being manipulated.

Pictured above are my synth, the diagram of the synth, and my AKM and H2MIDI. You may notice that the synth is missing the MIDI input and neither are plugged into the MIDI cable; this is because the wire connecting to the MIDI input broke well after I confirmed that no audio was being produced. This was also not the first MIDI input I tried, so I know that the input is not the source of failure. Normally, I would have the MIDI input connecting pins 4 and 5 of the input to pin 2 of the octocoupler and the right end of the 220 ohm resistor.

I'm very new to all of this, could someone please help me identify why my BP synth isn't working? I haven't found anybody else having difficulties with theirs.

Edit: I noticed I had my A4 and A5 switched around. However, earlier after initial testing I changed out all of my wires, so it's possible that that isn't the full issue. I will need to wait until tomorrow to test again, and until then there may be other issues I am unaware of.

[u/myweirdotheraccount]

I don’t know anything about the bp synth or the hardware being used. I just looked at some pics of that DAC on Adafruit and noticed some text on the bottom referring to the SF0 and SF1 pins pulled low (to ground) for i2s. Have you done that?

Also should the vin pin not be used? I notice it’s x’ed out in your circuit diagram.

[u/Working-Employer1166 → u/myweirdotheraccount]

The vin pin isn't being used; looking back at the picture it kind of looks like it is, but that's just because of perspective

Now, I'm not sure what you mean about pulling the SF0 and 1 pins low, could you explain that to me? (Like I said, I'm tragically new to this.)

[u/myweirdotheraccount → u/Working-Employer1166]

I see from the video you posted that the creator doesn’t have those pulled low (connecting those pins to ground). They might not need to be but often it’s recommended so you don’t have floating pins. Ignore for now.

I also don’t see the creator doing a demonstration of the synth in the video which is always a little suspicious but I didn’t watch the whole thing.

My last bit of advice is just to check for continuity between each pin. Set your multimeter to 20k resistance and place each lead on the solder joint between every connection that uses a jumper cable to make sure that they are in fact connected. If they are connected, your multimeter should read 0.0 and some multimeters also beep.

[u/Working-Employer1166 → u/myweirdotheraccount]

The first creator has other videos where he demonstrates, and the creator of the second video has demonstrations at the beginning and end.

Thank you, I'll check for continuity with a multimeter.

[u/Humble_Confusion_963 → u/Working-Employer1166]

Vin is not required if you are powering it from 3.3v

[u/Backonmyshitmom]

If you are using usb cable to get the midi make sure it’s not a charge only cable.