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Hobbytronics USB Host - USB to MIDI Din Thread
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Hobbytronics USB Host - USB to MIDI Din Thread
Hallmar
Ok so, I haven't seen any proper threads about DIY USB Hosts and what devices work with specific ones.

I bought a Hobbytronics USB Host with the MIDI Device software option and it works perfectly with a Korg Nanokontrol2.
Might be cool if other users with different controllers could try this out and post a confirmation in this thread.


Here's a video of my setup (will put it into a box later)
Link for the USB Host


Confirmed working:
Korg Nanokontrol2

EDIT: Added resistors and connected the reference to 3.3V
Quick diagram for how I connected it:
Hallmar
in hindsight i think that i need a 100 to 200 ohms resistor between the 5V line and pin number 4.
fitzgreyve
I have this working using an Akai MPK mini - output works fine, but you have to enable MIDI real time reception on the hobbytronics host if you want to clock it (arpeggiator) from an external source.

It seems that the midi is reference to the 3v3 (on board regulator) supply not 5V, so you need:
- 39R (not 220R) from +3v3 to pin 4
- 39R from Tx to pin 5

I have it working using these values.

I have spare PCBs but not panels for euro mounting :
https://www.muffwiggler.com/forum/viewtopic.php?t=161110&highlight=
Hallmar
fitzgreyve wrote:

It seems that the midi is reference to the 3v3 (on board regulator) supply not 5V, so you need:
- 39R (not 220R) from +3v3 to pin 4
- 39R from Tx to pin 5


hmm ok you are right, will change it then!

Yeah, clearly states in the schematic that the PIC is run off the 3.3V line.
Thanks!
Nantonos
Hallmar wrote:
in hindsight i think that i need a 100 to 200 ohms resistor between the 5V line and pin number 4.


Why?

According to the MIDI spec, for DIN MIDI output 3V3 you need 33R to +3.3V and 10R from the serial connection. For 5V those resistors are both 220R.

By the way Hobbytronics has a list of known supported devices http://www.hobbytronics.co.uk/midi-supported-devices. Any device that includes a built-in hub is not currently supported.
Hallmar
Nantonos wrote:
Hallmar wrote:
in hindsight i think that i need a 100 to 200 ohms resistor between the 5V line and pin number 4.


Why?

According to the MIDI spec, for DIN MIDI output 3V3 you need 33R to +3.3V and 10R from the serial connection. For 5V those resistors are both 220R.

By the way Hobbytronics has a list of known supported devices http://www.hobbytronics.co.uk/midi-supported-devices. Any device that includes a built-in hub is not currently supported.


Yeah, I posted that before I added the 33R(Edit: woops, put 39R instead of 33R, another mistake d'oh! ) resistors from the 3.3V Line, so that post was total bullshit, lol.

Yeah, I've seen that list smile) But it doesn't contain all controllers, so I think it would be a good idea to have some kind of a list of what works and doesn't.

I'd really like to know for example whether it will work with the Midi Fighter Twister or Keith McMillen K-Mix(got one in the post so I can atleast try that myself).
hamildad
need some help setting this up..

I wanted to install this in a Doepfer MCV4, and was planning to install it to the MIDI IN pins on the PCB. This is possible right?

I can take the power from the MCV4, or does it need to be 5V exactly?

For resistors, I need 33R on the 3.3V going to PIN 4
I need 10R on the TX going to PIN 5

and 220 on both 5V & 0V from the power supply?

help
Graham Hinton
hamildad wrote:

I can take the power from the MCV4, or does it need to be 5V exactly?

For resistors, I need 33R on the 3.3V going to PIN 4
I need 10R on the TX going to PIN 5


MIDI is a nominal 5mA current loop. The input circuit is defined by the standard: 220R in series with an LED (inside the opto isolator).

The loop current, 0.005A = (Vcc - 2V) / (2R + 220)
assuming 2V for the LED forward voltage (it isn't exactly, neither is Vcc, both have tolerances).
transposing:

2R = ((Vcc - 2V) / 0.005 ) - 220

for Vcc =3.3V

2R = 40, so make the Rs 22R each. They are in series and function as output current limiters to protect against incorrect connections. The top one might be shorted to 0V in which case it would draw 150mA and needs to be 1/2W. The lower one protects the output transistor and 10R is not a lot of protection depending what you think it might get connected to by mistake.

Quote:

and 220 on both 5V & 0V from the power supply?


I've done the maths so that you can do the arithmetic.
mokomo
Hobbytronics have 75 ohm resistors?
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