DIY USB host - MIDI DIN converter - USBpal released


#1

I just did a DIY (actually a DIM - do it myself) USB host to traditional MIDI DIN converter based on FTDI’s VNC2. It’s a fully-fledged MCU with two USB controllers. The complete USB protocol data processing is handled entirely by hardware so you only have to call APIs. The VNC2 runs a proprietary RTOS.
The design is straight forward and I tried to keep the part count as low as possible. I picked the VNC2 because it’s half the price of a pure USB host chip like MAX3421E which was used in other Arduino-based MIDI converters and also I wanted to do something new.

With this board you can use USB-only MIDI controllers to drive traditional MIDI hardware. USB power is supplied. Version 1.0 works really good. In this example I used a USB-only Korg Nanokontrol and a DIY synth called Shruthi - you may know :slight_smile: The final version will have two independent USB host interfaces and merge two devices into one MIDI out.

Here you can find all project resources (hardware and software). It’s open for discussion. Comments are welcome!

If there is some interest I could run a small batch (pcb only or full device). A metal case is also coming.

USB_MIDI_source.zip (3.2 KB)


#2

Great job!


#3

Definitely interested in one or two PCBs!


#4

Looks great. Certainly interested.


#5

Fabulous! A eurorack version, maybe with two separate channels, would be really popular. I’d be very keen to build one of those. A 1U nigh “Erthenvar” tile format might also be quite popular.

What is the license on your schematic and source files? If you make such things available publicly, it is always a good idea to be explicit about how they are licensed and how you want them to be used by others.


#6

wow, great! Will you sell pcbs? I’d be in


#7

Can I have a fully built one?


#8

Awesome!
Can i have a strange request? Also a normal DIN midi in? That can be merged with the usb midi in? Maybe only as extra solder holes on the PCB? Is this technically possible?

That would be perfect to use into a shruthi XT keyboard i’m planning to build.


#9

Quite interested in that ! Good job :slight_smile:


#10

I´m in for kit(s)!


#11

Depending on this MCU’s features, it might be cool to find a way to also offer multiple DIN MIDI INs and OUTs in addition to the two USB sockets you’re planning. If you don’t want to make the PCB bigger, you could include simple patch points for soldering wires.


#12

Count me in :slight_smile:


#13

Feature creep already :smiley:


#14

@all: Thank you very much for all the comments!

To give something away, the most promising way for me would be to sell ready built and tested gadgets because then I’m sure you get a working item. The risk of self-sourcing and soldering SMT would be that troubleshooting is hard since you can’t plug out the IC off a socket, changing components isn’t easy, populated components are hard/impossilble to identify… and so on, you know this. Selling PCBs would of cause be easy to I-know-what-I-do-guys.

Please keep in mind if you self-source you will need a programming/debugging dongle from FTDI (“VNC2 DEBUG MODULE”, approx. 25 EUR) and the windows-only toolchain from FTDI (free).

Eurorack: you can simply put it behind a 6 or 8 HP panel, skip the DCin connector, and plug it into the 5V rail. I consider to arrange a 6x2 eurorack pinhead.

Actually I wonder to change the 9V DC barrel plug to a USB micro connector to use a simple/cheapo USB power wallwart. Then the 5V regulator can be skipped. What do you think?

MIDI IN: Software wise this would be easy since the UART Rx is not used yet. But we would need the circuitry with optocoupler and a muuuch larger front panel… A solder point is easy but it’s neither fish nor fowl… More than 1 MIDI DIN I/O I don’t like because I only have 1 UART.


#15

A solder point makes a lot of sense from my point of view :wink: It means you can easily build it onto other gear that already has a midi in on it. Like the shruthi keyboard i’m planning to make.
But it could also be an existing/diy Midi to CV Module. You take the normal midi input already on the device. Disconnect it by braking a trace on the pcb (of the CV module) and ad the output of this thing to the place the midi trace was going to.
Maybe it sounds a bit to much like hacking for something new you are developing. I can also see more features for it. Like merging a midi controller with DIN midi with one with USB midi without the use of a computer.


#16

This is the case in progress. As you see it’s bullet-proof.


#17

(@6581punk: what is “Feature creep” in German?)


#18

This looks brilliant. If I am on the accumulation phase of the gear cycle when you make kits available I could well be interested. People have been after this for a while, there are lots of cool little controllers that need a USB host to play with MIDI synths direct. Great work!


#19

> Actually I wonder to change the 9V DC barrel plug to a USB micro connector to use a simple/cheapo USB power wallwart. Then the 5V regulator can be skipped. What do you think?

Keep in mind that these connectors tend to break very easily (depending on the model). 9v PSUs aren’t much more expensive

would the DIY version be THT?


#20

> [] the most promising way for me would be to sell ready built and tested gadgets […]

Completely agree.

> Actually I wonder to change the 9V DC barrel plug to a USB micro connector to use a simple/cheapo USB power wallwart. Then the 5V regulator can be skipped.

Makes sense. I would recommend using Mini USB and not Micro USB. Micro USB indeed tends to be a bit brittle as rumpelfilter mentioned, while Mini USB is pretty sturdy. Most people already have too many USB power supplies lying around anyway.

> MIDI IN: Software wise this would be easy […]

IMHO having both a DIN MIDI IN and a DIN MIDI OUT is of more value to most people than having two USB host sockets since you can use a USB HUB to connect multiple instruments to the host.

A practical examples of where DIN MIDI IN to USB MIDI makes sense would be a case where you want to use a DIN MIDI OUT only full-size keyboard to play and control a Teenage Engineering OP-1.