Help getting started (MCT, Megadrum v2.8, USB)

[dmitri]

Try one more thing. Turn it on. Start measuring voltage on pin 3 of the LCD connector.
Press the key UP and keep it pressed for a few seconds. Was the voltage on the pin 3 of the LCD connector changing??

Yes, the voltage went down.

Press the key DOWN and keep it pressed for a few seconds. Was the voltage on the pin 3 of the LCD connector changing?

Yes, the voltage went up.

This is a good sign. It means that Atmega is working although shorts or breaks may prevent the whole thing from working properly.
Take the multiplexer IC connected to pin 40 of Atmega out of its socket. Power the board up and touch the pin 40 of Atmega with tweezers or a thin screwdriver. Your fingers' bare skin must be in contact with metal surface of the tweezers or the screwdriver. While touching and and then releasing the pin 40 monitor voltage on the pin 27 of Atmega. Does it change? What is it?

[Thurston]

I'm having trouble understanding what I am to do. I understand that you want me to remove the 74HC4851N IC that connects to pin 40 of the Atmega and to power up the board. Then you want me to touch pin 40 of the Atmega with a metal object that also touches my finger.
I don't understand what you mean by "While touching and and then releasing the pin 40 monitor voltage on the pin 27 of Atmega. Does it change? What is it?" Can you clarify this please?

[dmitri]

I'm having trouble understanding what I am to do. I understand that you want me to remove the 74HC4851N IC that connects to pin 40 of the Atmega and to power up the board. Then you want me to touch pin 40 of the Atmega with a metal object that also touches my finger.
I don't understand what you mean by "While touching and and then releasing the pin 40 monitor voltage on the pin 27 of Atmega. Does it change? What is it?" Can you clarify this please?

Touching the pin 40 you're trying to induce an input voltage on the analogue input of Atmega which will simulate an input signal on the first 8 inputs. Monitoring voltage on the pin 27, which controls MIDI LED, will eliminate possibility that the LED is faulty/incorrectly connected and thus will provide direct information if Atmega registers any input signals.

[Thurston]

The voltage at pin 27 reads 4.9 VDC when pin 40 is not touched. When pin 40 is touched with tweezers the voltage drops to less than 1 VDC, rises back up to 4.9 and continues to fluctuate.

[dmitri]

The voltage at pin 27 reads 4.9 VDC when pin 40 is not touched. When pin 40 is touched with tweezers the voltage drops to less than 1 VDC, rises back up to 4.9 and continues to fluctuate.

Another good sign. If you still couldn't see the MIDI LED to light up than is is either connected in reverse, faulty(very unlikely) or a resistor connected to the LED has too high resistance(if it is 1K, replace it with a 330 Ohm resistor).

[dmitri]

Also, when you touch the pin 40 of Atmega monitor voltage on the pin 15 of Atmega. Do you notice any changes? What are they? What about voltage on the pin 18 of PIC18F2550? When you have MCT running and you touch the pin 40 of Atmega do you see it registering any MIDI activity?

[Synthex]

a resistor connected to the LED has too high resistance(if it is 1K, replace it with a 330 Ohm resistor).

If you use the LED in the kit, the 1K resistor is a good value.

[Thurston]

The voltage at pin 27 reads 4.9 VDC when pin 40 is not touched. When pin 40 is touched with tweezers the voltage drops to less than 1 VDC, rises back up to 4.9 and continues to fluctuate.

Another good sign. If you still couldn't see the MIDI LED to light up than is is either connected in reverse, faulty(very unlikely) or a resistor connected to the LED has too high resistance(if it is 1K, replace it with a 330 Ohm resistor).

MIDI LED was installed in reverse. I have corrected this and everthing appears to be working. I apologize for my newb-ness. I'm mostly a mechanical guy and am learning as I go .

When I hit the piezo the LED now blinks (and also on start up). MCT is also registering the hits. Thanks dimitri and synthex for your patient explanations and troubleshooting tips. I'm am looking very forward to figuring out how to get the MIDI into Superior drummer and also completing my DIY kit knowing that this important piece of the puzzle is working as it should .