Crazy Idea - MT32 WaveBlaster Card

[gdjacobs]

If it's ok with you, I can merge with the existing "Munt on Pi" thread and move it to Sound?

Yeah, I followed that thread pretty closely; definitely good work. My attempts here are to essentially productize that idea into a unique form factor. I don't disagree with merging the two... for sure both belong in Sound.

That's my thinking as well. I want to create a synth module capable of mounting in a drive bay or on the desk that can handle all LA synth or sample based synthesis.

[hard1k]

MuntBlaster?..

[RJDog]

MuntBlaster?..

Ha! That's not bad actually...

[gdjacobs]

MuntBlaster?..

LABlaster?

[PhilsComputerLab]

MB-32

Midi Blaster 32

[ab0tj]

Teh Muntificator

[hard1k]

LABlaster?

BLABLAster

[BloodyCactus]

The Multi Timbral Muntnificence 32

[brostenen]

M-Daughter-32

[RJDog]

MuntBlaster?..

MB-32

MB-32 = MuntBlaster-32
32 because... Cortex A7 is 32 bit processor.... I guess

Sold! (or until something better comes to mind)

[RJDog]

First draft of the WaveTable-to-OrangePiZero card complete; the host board (i.e. the board this card will go in to make it a stand-alone unit) yet to come.

[ab0tj]

Cool! Looks like this one will be fun

[hard1k]

Maybe I will be totally wrong here (as I'm not a hardware design engineer), but looking at the Orange Pi Zero picture the lower 26-pin header ("expansion port") on the MB-32 seems to be misplaced by 1 pin to the left - judjing from mutual placement of this header and the serial debug port as well as its alignment against the upper 13-pin "function interface".

[RJDog]

but looking at the Orange Pi Zero picture the lower 26-pin header ("expansion port") on the MB-32 seems to be misplaced by 1 pin to the left

Holy buckets of earth, batman! You are exactly correct... good catch. Now I feel like an idiot. Not sure how I screwed that up so badly in the footprint...

[hard1k]

Don't worry, that happens
When we produced the first batch of the GUS PnP RAM Adapter, somehow we chose the wrong thickness for the PCB - 0,8mm instead of 1,0mm. We had to manually add additional solder to the contacts in order for the adapter to sit well in the SIMM sockets, otherwise they just fell out...

You're welcome

[RJDog]

Well... here is the updated version, this time with the correct footprint for the Orange Pi Zero. Still working on the host board. Thanks again, hard1k, for catching the misalignment.

[Ariakos]

This is a neat project. But the things I would do for an MT-32 in a PCMCIA form, though...

[RJDog]

This is a neat project. But the things I would do for an MT-32 in a PCMCIA form, though...

Well.. there do seem to exist PCMCIA MIDI cards....

But in other news, I have discovered a critical error in my design... my current design is based on the assumption that the Orange Pi Zero accepts 5V on the GPIO. It does not. It is 3.3V and apparently is not super tolerant of higher voltages. I'll have to rethink this.. implement a logic level converter or something...

[gdjacobs]

Shouldn't be too hard to fix using voltage followers.

[RJDog]

Yeah, the MOSFET route seems to be a bit on the expensive side, but doable, and quick googling seems to indicate its a popular solution.

I am thinking about using some non-inverting buffer logic chips, i.e. the 74LV125A can operate at and output 3.3V but inputs accept up to 5.5V regardless of Vcc; and 74HCT125N can operate at and output 5V and inputs accept as low as 2.1V for "high" signal. My biggest concern would be to make sure the buffers can switch fast enough to accomodate the 31250 baud rate. The TI part I'm looking at says its switching time is 4.7ns, which equates to roughly 2MHz, so that should be okay, I think?