Some changes to schematics (original "I screwed up")

[dmitri]

This topic is now out of date because the correct schematics have been up there for quite a while. So I move it out of the announcements.

Hi,

It appears I screwed up my development Digital board but the weird thing is that estregan , see this thread, might have the same problem as I have.
First of all I should say that the MegaDrum module I use for drumming works fine - it communicates fine with a PC over both standard MIDI and FT232 based USB board, i.e. MegaDrum Controller (Sysex messages) works fine with it.
Now, with my development board I experience a strange issue: whenever I send a Sysex message to this board over USB MIDI(both Synthex's and AVR-CDC) it causes MegaDrum to reset. Sending Sysex over standard MIDI works fine, but the weirdest thing is that if I keep standard MIDI connected to the same PC but send Sysex over USB MIDI it works fine again!

So, until I resolve this issue, I won't be making any firmware updates.

I think I've managed to solve the problem:

In MegaDrum32 Digital board: R26 - from 220 to 4k7 (thanks to Synthex for the suggestion)
In MegaDrum8 Digital board: R21 - from 220 to 4k7
In AVR-CDC USB board: R4 - from 470 to 1k
In PIC18F2550 USB board: R4 - from 470 to 1k

After these changes Sysex doesn't cause any problems anymore, at least on my dev board. Both Synthex's MIDI USB and AVR-CDC work fine for me.

[Synthex]

It is only the latest version of firmware ?

[dmitri]

It is only the latest version of firmware ?

No, it doesn't depend on firmware version. I tried it with very old versions with the same effect. And as I said it works fine on my MegaDrum module which I use for drumming with the latest firmware in it. It is something in hardware, e.g. loose connection somewhere, floating ground and etc.

[Synthex]

Personally, I changed the resistance R26 from 220 ohm to 4.7 Kohm.

[dmitri]

Personally, I changed the resistance R26 from 220 ohm to 4.7 Kohm.

Probably good idea, but don't think it has anything to do with my problem as I even tried disconnecting R25 (not R26 you mentioned) and still every Sysex was causing MegaDrum to reset.

[Synthex]

For me, when I send a Sysex message to my MegaDrum32 over Synthex's USB MIDI, the MegaDrum32 responds correctly with the dump configuration ...

[estregan]

Sorry if I may be one of the reasons why this happened. I just wanted to make my megadrum to work over AVR-CDC. I would really like to help on debugging/troubleshooting but I don't know much technical stuff about electronics.

I hope you resolve the problem soon. I'm going to try putting an LCD on my megadrum to see if it resets same as yours.

[dmitri]

For me, when I send a Sysex message to my MegaDrum32 over Synthex's USB MIDI, the MegaDrum32 responds correctly with the dump configuration ...

Just as mine assemled (not development) module with FT232 USB which I use for drumming. Clearly it's neither a USB board nor firmware issue but electrical.

[dmitri]

Sorry if I may be one of the reasons why this happened. I just wanted to make my megadrum to work over AVR-CDC. I would really like to help on debugging/troubleshooting but I don't know much technical stuff about electronics.

I hope you resolve the problem soon. I'm going to try putting an LCD on my megadrum to see if it resets same as yours.

Don't worry, problems exist to be solved and learn from them:) This problem will be solved just as well.

[Synthex]

Without problem, it would not be funny !

Together we advance !