Could I have fried the atmega?

[ignotus]

Hi again

I've been fiddling around a bit - changed the crystal, 22pf capacitors, inductance, checked for shorts, bad connections, tried with 3 different LCD's, 2 atmega's... I'm starting to get a bit desperate... it's been working beautifully for 2 months and now I'm pretty stumped...

Megadrum flashes midi activity light when starting up and afterwards sends midi signals normally - but the right half of the screen just shows black blocks, and the left half is blank. It seems to be a problem with screen handling, caused by some mistake or a faulty component I just can't pin down. Voltages seem OK too.

Any suggestions would be greatly appreciated as to what this could possibly be

[dmitri]

So are you saying that MegaDrum is functioning properly except LCD handling? (I'm assuming that the programmer cable is disconnected)

Then try/check this:
1. Disconnect the keyboard. Turn on MegaDrum. Still problems with LCD? Go on.
2. Check for short circuits on pins/traces for keyboard and ICP connectors.
3. Check for short circuits/continuity on LCD wires. It may appear they're ok but in fact lost continuity.
4. Radical one. Resolder LCD wires.
5. Try another LCD.

[ignotus]

Fixed!!!

First of all thanks a million Dmitri for always being there ready to suggest and help out at the drop of a hat - cheers!

Turned out it was the damn LCD... the thing was that the first time I turned on Megadrum with the new LCD all the characters were messed up, and that was completely baffling me; it took repeated rebootings for it to suddenly show the proper display. I've noticed this behaviour happens each time I swap LCD's - I have to restart Megadrum a number of times, and once it shows up right, it stays that way over every new reboot. Strange... The original LCD was a a blue backlight one and the others I tried are the yellow type, if that's any indication...
Anyway, thanks again!

[dmitri]

Great you've managed to fix it!
I still think you have a loose connection somewhere along Atmega->traces->connector->wires->LCD.

[Beamtreetaker]

I also got some strange issue.......... My megadrum worked nicely for the last 2 weeks, but now it won't start. The display shows just one line of black blocks and the 2nd line is empty. The 'USB device detected' message appears when I connect the unit but neither the midi led flashes nor are any midi notes sent when I hit pads, so it's not only the display that's not working. I then cleaned the PCB with some electronic cleaning fluid and afterwards Megadrum was operating again, but now (some hours later) it's like dead again (apart from the USB detection). Do you have an idea what could be the problem here? Is a bad soldering point likely or may a defect capacitor be the reason? Any chance of remote diagnosis?
Thanks in advance

[Synthex]

The display shows just one line of black blocks and the 2nd line is empty.

You lost the firmware of the Atmega

Reset MegaDrum while holding the key LEFT. It'll ask you to press the key DOWN. If you changed you mind you can reset MegaDrum again without holding any keys and it will boot an old firmware. If you press the key DOWN, it'll erase the old firmware and will wait for the Sysex with a new firmware. Now in MIDI-OX go to Actions->Send->SysEx File... and choose the firmware *.syx file you've prepared beforehand. The update will take around 5 seconds and after it's finished MegaDrum will reset itself and boot the new firmware.

Bootloader :
http://www.megadrum.info/forums/viewtopic.php?f=3&t=111

Problem with firmware getting erased by random :
http://www.megadrum.info/forums/viewtopic.php?f=3&t=147

[Beamtreetaker]

Mhhh.. are you really sure? I'm doubting that a little because in the meantime it was working for some hours.
But if your assumption is correct..will I have to build a LPT-ISP cable now or can I use USB to flash a new firmware (assumed the chip is not damaged, too)?

Edit: Oh, you were faster! Thanks a lot, Synthex! =) =)

[Synthex]

Mhhh.. are you really sure? I'm doubting that a little because in the meantime it was working for some hours.
But if your assumption is correct..will I have to build a LPT-ISP cable now or can I use USB to flash a new firmware (assumed the chip is not damaged, too)?

Edit: Oh, you were faster! Thanks a lot, Synthex! =) =)

You can use USB to flash a new firmware. (UP )

[dmitri]

I personally doubt it's firmware been erased. I think it's loose connection/soldering somewhere to +5 or a shortcut somewhere.

[Synthex]

I personally doubt it's firmware been erased. I think it's loose connection/soldering somewhere to +5 or a shortcut somewhere.

Just do the test : Reset MegaDrum while holding the key LEFT, and see the LCD ...
if you can read "press DOWN", it's the firmware ...
If not, it's a shortcut ...