Another bizarre problem!

[ohawker]

Ok, temporary bizarre workaround, you know the capacitor next to multiplexer 3? 1uF? Well if i connect a second capacitor to those terminals AFTER the laptop has rejected the MegaDrum, it recognises it and opens MIDI ports! I don't know what that capacitor does (some kind of DC smoothing, I'm guessing? For Multiplexer power? Anyway, that seems to work, any suggestions based on this?

Thanks

[Synthex]

Ok, temporary bizarre workaround, you know the capacitor next to multiplexer 3? 1uF? Well if i connect a second capacitor to those terminals AFTER the laptop has rejected the MegaDrum, it recognises it and opens MIDI ports! I don't know what that capacitor does (some kind of DC smoothing, I'm guessing? For Multiplexer power? Anyway, that seems to work, any suggestions based on this?

Thanks

Change this capacitor for an other bigger one (like 47 uF).

[ohawker]

Ok, that workaround seems to have stopped working, however its changed again.

Right, basically my firmware has vanished from Atmega (I think a crossed line on the keyboard put it in firmware update mode). At any rate I have been trying to SysEx the firmware over to the Atmega, but I have hit some problems:

My laptop always recognises it as USB Audio Device, although 10% of the time it doesn't open ports and DM returns 'Code 10: The Device Cannot Start'. When it DOES work, it opens 'MegaDrum MIDI USB' IO, which made me think it was sorted but when I try and open the ports in MIDI-OX, the program freezes and locks down completely. It doesn't do this if the ports are opened by default, but when I try and use them, nothing happens. I try and re-open the ports, and it freezes

I basically have been trying to SysEx the firmware to MegaDrum, but this is proving hard with no MIDI interface! And I am working on a laptop so no parallel port!.

I'm thinking that I will have to just buy a new Atmega preprogrammed with firmware, and not use the USB interface, just wire it through my MIDI keyboard MIDI In! Although I would rather not resort to this, so has anyone got any last minute suggestions or shall I go ahead and ask Synthex very nicely?

[dmitri]

Now you mentioned possible short circuit on the keyboard traces. Until you sort out soldering quality you will be getting all sorts of troubles. With carefully soldered MegaDrum boards USB MIDI gets detected rock solid all the time, not just 90%. And MIDI date flow without any problems as the one you have while trying to upload a new firmware.

[ohawker]

Yeah i guessed from other peoples posts and believe me, I really regret not getting a £10 Maplin kit to practice first, this was my first ever project, and I'm now suffering from the mistakes that I learned from! I would love to be able to start fresh with a 2.7 Kit + components from Synthex, but I can't afford it

The short on the keyboard was only a very recent thing, a recent connection not done properly. I'm hoping that when the MegaDrum is built and the creases ironed out as well as I can, it will function properly. I have no alternative at the moment I admit its not ideally made, but its all i've got

[dmitri]

My advice: be thorough, look over all traces and soldering points with a magnifying glass. Make sure you don't have short circuits. Resolder all the places which raise slightest suspicions. Then look over again until you absolutely sure everything is right.