USB to MIDI converter?

[MS-SPO]

Hi,

a while ago I bought a Nektar impact LX 61 keyboard, which has an USB connector only (see bottom of http://www.nektartech.com/Products/Impact-LX49 ). That worked fine (with some latency) connected to a PC and making music with a DAW.

Now I'd like to connect it directly to other MIDI devices, like my e-drum, which accepts MIDI controllers for backing parts, through regular MIDI connectors.

I'm sure there is a solution to this, but I'm not sure which one will work when searching the web. E.g. there are some USB/MIDI converters like the Prodipe MIDI USB 4i/4o (http://www.prodipe.com/en/products/interfaces/item/60-interface-midi-usb-4in/60-interface-midi-usb-4in), but USB seems to be dedicated to PC only. I'm not sure if USB/MIDI cables with integrated converter will do (e.g. http://www.thomann.de/gb/terrasoniq_midi_one.htm ).

What I'd like to have is a stand-alone solution, which converts the LX's USB connector into a regular MIDI connector, so I can plug it directly into other MIDI devices. Power supply from the solution would be nice to have over USB, as that's the LX's normal mode - alternatively I could attach an extra power supply to the LX (right left to the USB port). [error: that's for a foot switch]

I welcome your suggestions ; -)

Thanks from Germany, Michael

Edited November 15, 2015 by MS-SPO
Mainly removing typos while doing check reading

[freddy]

Michael,

 

though not being an expert on this topic I don't think you'll get it working that easy with ordinary USB-MIDI converters. The reason is that with two connected USB devices one has to act as a host (controlling the communication), the other as a guest (performing the tasks). Host is usually the PC/MAC and guest is e.g. the MIDI converter or the keyboard in your case. Connecting keyboard with an ordinary MIDI converter will effectively connect two guests with no host to control the communication, so what you need is a device that acts as a host, e.g. http://www.kentonuk.com/products/items/utilities/usb-host.shtml. I'm not saying this particular one will work but in general, these are more costly devices compared to USB guest converters and more intelligent (which is a feature you probably won't use in the setup described), this particular one seems to be dumb enough so it doesn't cost you a fortune, though.

 

Hope this helps,

freddy

[MS-SPO]

Thanks freddy, you put my gut-feeling into words ; -)

"USB host" is certainly a good keyword to look for.

Thanks, Michael

[Shuriken]

What you want can be achieved by building CORE_STM32F4 and buying a OTG cable. Check out this topic. Or if you want something ready-made then iConnectMidi4plus

[MS-SPO]

Hi Shuriken,

thank you, the CORE_STM32F4 sounds interesting. I see I can order the STM-board from many places, like e.g. this one: http://shop.mymcu.de/index.php?sp=article.sp.php&artID=200072 .

About the lower board shown (see after "Soldering guide in http://www.ucapps.de/mbhp_core_stm32f4.html ) ... do you know if it's available as a finished product (Couldn't find it; perhaps I don't need it for my application?) ? Where to buy the MIDI-connector board http://www.ucapps.de/mbhp_midi_io.html ?

I'm enticed by the low-cost solution.

Thank you Shuriken. Best regards, Michael

Edited November 15, 2015 by MS-SPO

[Shuriken]

Hi Michael,

This community is about DIY. So the stuff used here is usually just that. So the answer is no, no pre-build stuff. 

[MS-SPO]

Hi Shuriken,

no problem ;-)

[MS-SPO]

Ok, I understand I have to install, upload, bootload some thingies to make the STM32F4-Discovery-board run .

One thing I couldn't find out: if I want to attach just one MIDI-OUT connector (supplied from my USB-keyboard attached to the STM32F4-Discovery-board), where to connect it to the board? I.e. what are the relevant  pins from the Discovery board?

Thanks, Michael

 

 

Edited November 16, 2015 by MS-SPO
too many graphics included ;-)

[latigid on]

Hi Michael,

Here you can find more info and pin assignments:

http://www.ucapps.de/mbhp_core_stm32f4.html
http://www.ucapps.de/mbhp/mbhp_core_stm32f4.pdf

You will have to close the MIDI current loop:

http://www.ucapps.de/mbhp/mbhp_midi_io.pdf

You can see it should have an optocoupler on the input side, and series resistors/pull up on the output side.

[MS-SPO]

Thank you latigie on,

yes, I saw those and was hoping for a shortcut. Example, just guessing: "connect port PD4 to pin 4 of MIDI out, and ground MIDI out pin 5, both via series res. 220 ohms". Sth. like that. Else, it's prone to errors (and I'm good in making those ;-)

 

Just to make sure: once this board has been set up and configured it will always run stand alone, i.e. without any further PC-connection? Connect MIDI keyboard on USB, MIDI OUT to e-drum by MIDI cable, switch it on, reset it, done. Play. Retire the PC. Is it that?

Best, Michael

Edited November 16, 2015 by MS-SPO

[FantomXR]

Just to make sure: once this board has been set up and configured it will always run stand alone, i.e. without any further PC-connection? Connect MIDI keyboard on USB, MIDI OUT to e-drum by MIDI cable, switch it on, reset it, done. Play. Retire the PC. Is it that?

Best, Michael

I'm interested in this too. I tried the USB-Host-Mode two weeks ago with two different devices and I was not able to get it working...

As far as I know the STM automatically boots into Host-Mode, if a usb-device is connected to the mini-usb. But how do I make f.e. routings? f.e. where do I set the midi ports the signal of the device is send out to. The core was not reachable via the micro-usb, if a device was attached to the mini-usb.

[CJ55]

@FantomXR: you have to connect the USB-device to the micro-USB port, not the mini-USB port! And you need a USB OTG adapter cable. Booting the STM32F4 with this adapter cable activates the USB host mode.

You can use the mini-USB port to power the board, though. Or use an external power supply.

[MS-SPO]

Michael,

...  acts as a host, e.g. 

http://www.kentonuk.com/products/items/utilities/usb-host.shtml.

 I'm not saying this particular one will wo...

freddy

Hello freddy,

this one seems to do the same job at a lower price: https://supr.com/mode-machines/products/cerebelusb-usb and is Adruino based (which may be beter or worse than STM, probably better).

best, Michael

Edited November 18, 2015 by MS-SPO

[MS-SPO]

Thank you latigie on,

yes, I saw those and was hoping for a shortcut. Example, just guessing: "connect port PD4 to pin 4 of MIDI out, and ground MIDI out pin 5, both via series res. 220 ohms". Sth. like that. Else, it's prone to errors (and I'm good in making those ;-)

 

Just to make sure: once this board has been set up and configured it will always run stand alone, i.e. without any further PC-connection? Connect MIDI keyboard on USB, MIDI OUT to e-drum by MIDI cable, switch it on, reset it, done. Play. Retire the PC. Is it that?

Best, Michael

Just wondering, why nobody was willing to reply to these questions, yet.

For the port-to-MIDI wiring the problem comes from the grey cable connecting both modules: which pin wires to which pin? That's not 100 % clear from looking at the board schematics. I can guess it, but I prefer to know it.

Also, my question "is it stand-alone or do I need a computer connection always" should be a no brainer for the experienced Discovery user ; -)

So, I welcome your information. Thanks + best, Michael

 

[latigid on]

Hello freddy,

this one seems to do the same job at a lower price: https://supr.com/mode-machines/products/cerebelusb-usb and is Adruino based (which may be beter or worse than STM, probably better).

best, Michael

The performance of Arduino-based controllers is generally worse than many of the alternatives e.g. Raspberry Pi etc.

 

 

Just wondering, why nobody was willing to reply to these questions, yet.

For the port-to-MIDI wiring the problem comes from the grey cable connecting both modules: which pin wires to which pin? That's not 100 % clear from looking at the board schematics. I can guess it, but I prefer to know it.

Also, my question "is it stand-alone or do I need a computer connection always" should be a no brainer for the experienced Discovery user ; -)

So, I welcome your information. Thanks + best, Michael

 

I haven't tried running the STM32 F4 Core in Host mode with a computer connected or not. The STM32 F1 Core works just fine standalone.

For your wiring question: you have all the info you need in the schematics. As you choose to use a non-standard method (would be very simple with the carrier PCBs) you will have to join the dots yourself.

 

[MS-SPO]

For your wiring question: you have all the info you need in the schematics. As you choose to use a non-standard method (would be very simple with the carrier PCBs) you will have to join the dots yourself.

Hi latigid on,

I was contemplating about your answer for a while, which I percieved, without trying to be offensive, as questionable.

However, luckily the information I was looking for in fact can be found in the schematics. For the quick reader:

• connect port PA2 to connector MIDI OUTA
• connect port PD8 to connector MIDI OUTB
• include the 2 resistors of 220 ohms, each, as indicated in the MIDI_IO schematics.

For details please check:

• http://www.ucapps.de/mbhp/mbhp_core_stm32f4.pdf , J11E, pins MO1 and MO2
• http://www.ucapps.de/mbhp/mbhp_midi_io.pdf , J1 or J2, J4 (leading to OUTA), J6 (OUTB).

So non-standard wiring, as you called it, is pretty straight forward. See, simple question, simple answer, especially when the hardware is  available (which I don't have) for an ohmmeter or so. As I assumed the support board, the grey connector cable and the MIDI_IO board just form a long wire with some complicated geometry .. but it remains just a wire-connection. (The LEDs and their buffers parallel to J1/J2 may or may not be used.)

So, I can save 80 % to 90 % of the "standard-components", and associated assembly time. That could be a beginning. However, I'm waiting for a reply from http://www.hobbytronics.co.uk/usb-host-mini , which could be even easier. Have to check, which reduces my overall risk ; -)

Best, Michael

[freddy]

Hello freddy,

this one seems to do the same job at a lower price: https://supr.com/mode-machines/products/cerebelusb-usb and is Adruino based (which may be beter or worse than STM, probably better).

best, Michael

Good to know, the other one was just first google result for inspiration.

[MS-SPO]

Dear all,

I'd like to thank you all for your support and helpful hints on my initial question: you all helped me to make up my mind.

Finally, after checking with my own hourly rate I today received my CerebelUSB unit, which works fine (plug & play-music) ; -)

Best, Michael

[freddy]

Glad to hear it worked for you, I hope you'll go the DIY way when solving next issue 

[FantomXR]

On 18.11.2015 at 7:21 PM, MS-SPO said:

So, I can save 80 % to 90 % of the "standard-components", and associated assembly time. That could be a beginning. However, I'm waiting for a reply from http://www.hobbytronics.co.uk/usb-host-mini , which could be even easier. Have to check, which reduces my overall risk ; -)

 

Any news on this?