GM5 mini PCB connection to PIC core

[artyman]

Hi, I'm in the final planning stages of a 2-core MBLC and intend to use a GM5 mini PCB for USB connection to my PC.

reading up on the GM5 module, it says the headers at J6 can be used for direct digital connection to J11 (core).

Does this mean I can leave out the opto-couplers on both the GM5 and the core? There will be no external MIDI connections, as this is planned as a completely self-contained unit.

Many thanks in advance

[Digineural]

Depends, if the LC boards and the GM5 are sharing the same ground and +5, (i.e. not from the PC) then it should be ok for a direct connection. If you're using the prefabbed boards from Tim or Mike, then you're best using the optocouplers to isolate the rails since its likely that you're not going to power the whole system over USB. Without it, you could do some amazing damage to both the LCs and your PC

[artyman]

The whole thing will be powered from a 12vDC input with 5V derived from that.

The USB power option will be disconnected.

The plan there is to only connect the D+ and D- from the USB socket via a pin header on the PCB. The ground will come from the common PSU ground via J7.

Edited November 7, 2012 by artyman

[Digineural]

I've completed a design like that which worked fine so far. If its critical though, I would get a second opinion. But I think you're ok. If I'm reading the datasheet right though, UGND (pin 28 next to D+) should still be connected to the USB ground (Per page 96).

[artyman]

Gotcha !!.. I was wondering if the USB ground needed to be connected as well.

Cheers