PCB DESIGN - All In One v2.5 - 32 inputs with 74HC4851

[jamdat]

My megadrum purchasing is coming along nicely. Just a few more selections and then I'm going to ask for a review before I buy what is left.

In the meantime, I have been reading about the trials of printing the PCB design to the correct scale. Since I have the 40 pin header, I decided to test out the print. Sure enough, like gastric, I first got a 10 page PCB, then several PCB's that were off by one pin. Eventually, I solved the problem by importing the gif into Photoshop, resampling it, and cropping a few pixels. I messed up a tiny bit and the top and bottom layers are out by about a pixel. Considering that it works out to 1/600th of an inch (0.04mm for us metric folk), I'm not concerned. The 40 pin header lines up perfectly now.

My small contribution for now will be the files that I used, in PDF format ready for printing. I hope they are of some help and that they save somebody else some headaches.

[japi]

Hi. I don't seem to get the 74HC4851 here, but i get a 74HC4051. It is the same?
Thanks

[dmitri]

No, they're different. You must use 74HC4851 with the Synthex's schematic.

[japi]

Thanks.
I have a few questions, to avoid hijacking this thread, can you see this?

viewtopic.php?f=3&t=329&p=4334#p4334

[gastric]

Can someone confirm the area circled in RED here is supposed to be jumpered with a wire? It looks like it should be according to the graphic, but it seemed like an odd place for a manual jumper instead of a hard connection via the trace since there's no components in the way.

[Synthex]

Can someone confirm the area circled in RED here is supposed to be jumpered with a wire? It looks like it should be according to the graphic, but it seemed like an odd place for a manual jumper instead of a hard connection via the trace since there's no components in the way.

It's a wire.

[gastric]

Some questions:

* I've seen some users with what appears to be a 3 way toggle switch on the chassis but it's not clear what function that has.
* If you do not use USB you have to provide external power. But I do not see any board connectors for said power source. And if you just use the USB header on the board to provide power how do you wire it so you can use external power or USB and more importantly to create it in a safe way so if you accidentally have external power connected AND USB at the same time you don't damage something? Maybe that's my answer for the previous question.
* My Trigger IO provides similar functionality - external power for use with MIDI or USB which can provide it's own power.. It also has a dedicated on/off switch which appears to work even when connected over USB only (just tried it). I don't see any power switch feature provided on the board though I'm assuming I could wire one into the USB/power connector on the board easily enough by intercepting PIN1 on the USB header. Again, maybe that's the answer to my first question?

Many thanks.

I'm missing a few components so I'm placing (fingers crossed) one last order from Mouser and want to make sure I order everything I could possibly need.

[Synthex]

* I've seen some users with what appears to be a 3 way toggle switch on the chassis but it's not clear what function that has.

To select Hi or Low impedance HiHat pedal input ...
To switch on or switch off the module ...

* If you do not use USB you have to provide external power. But I do not see any board connectors for said power source. And if you just use the USB header on the board to provide power how do you wire it so you can use external power or USB and more importantly to create it in a safe way so if you accidentally have external power connected AND USB at the same time you don't damage something? Maybe that's my answer for the previous question.

With this version, if you do not use USB you have to provide external 5 volts power on the USB header

* My Trigger IO provides similar functionality - external power for use with MIDI or USB which can provide it's own power.. It also has a dedicated on/off switch which appears to work even when connected over USB only (just tried it). I don't see any power switch feature provided on the board though I'm assuming I could wire one into the USB/power connector on the board easily enough by intercepting PIN1 on the USB header. Again, maybe that's the answer to my first question?

Yes you can

[gastric]

I don't see anything related to pedal impedance on the main board nor the jacks board. Can you point that out for me? Or is that simply not a feature on the V2.5?

For the external power what kind of problems would happen if you had the USB and external power connected at the same time?

[Synthex]

I don't see anything related to pedal impedance on the main board nor the jacks board. Can you point that out for me? Or is that simply not a feature on the V2.5?

Low impedance is the normal pedal input.
Hi impedance is on pin 33 on the Atmega.

For the external power what kind of problems would happen if you had the USB and external power connected at the same time?

You can't connect both as the same time.