MIDI interface board - long shot!

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Gold Markclawson
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Posted by clawson: Wed. Sep 9, 2020 - 01:33 PM
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I thought this would be simple. I just want a board that is pretty much nothing but a 6N138(/6N137) and a 5 pin MIDI jack to be able to connect a MIDI signal into the UART of a micro but can I find such a thing cheaply?

 

Major suppliers like Sparkfun and Adafruit seem to have boards that are stupid prices like $20+ while I'm talking about something that has a $1 IC, a diode, a couple of resistors and and a 5 pin DIN socket. Sure I can find such things on ebay/Amazon/AliExpress/Banngood/etc (eg https://www.ebay.co.uk/itm/MIDI-Shield-Breakout-Board-for-Arduino-UNO-R3-AVI-PIC-Digital-Interface-Adapter/322579032922  )but they are all for delivery from CN with delivery dates out in October. Surely someone somewhere does a nice little interface board for just a few bucks and with a reasonable delivery time?

 

BTW this is a ref circuit from the PJRC/Teensy site that kind of displays what I am looking for:

 

and because I only want "IN" not out that actually reduces to:

 

 

I mean, how hard can it be to find a little board with just 6 components on it? While it would be daylight robbery I figure such a thing could cost up to £10/$15 perhaps but beyond that they're having a laugh.

 

(actually that's one thing I've noticed - MIDI electronics appears to be a licence to print your own banknotes!)

 

PS and yeah I guess that in the limit I just buy the bits and make it up on a breadboard but I was kind of looking for the solidity/simplicity of a ready made up little board. Oh and if I was to do this is there any UK component supplier with small/no delivery costs? I don't want to pay £3 for some components then £6 to get them delivered or something!

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jgmdesign
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Posted by jgmdesign: Wed. Sep 9, 2020 - 01:46 PM
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Simonetta is a MIDI maniac based on his/her posts in the past..... maybe some insight will arrive.

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

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ki0bk
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Posted by ki0bk: Wed. Sep 9, 2020 - 01:50 PM
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clawson wrote:
Major suppliers like Sparkfun and Adafruit seem to have boards that are stupid prices like $20+

Well unless you want to make 100k+, stock, sell and ship the same, that is not really that bad a price, compare to making it yourself in qty of one or two.....

If you still think its overpriced, then compete and make a fortune!  smiley

 

Jim

 

 

 

(Possum Lodge oath) Quando omni flunkus, moritati.

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obdevel
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Posted by obdevel: Wed. Sep 9, 2020 - 02:00 PM
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Worth a look on Tindie. A lot of stuff comes from overseas but this is a European supplier: https://www.tindie.com/products/...

 

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Simonetta
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Posted by Simonetta: Wed. Sep 9, 2020 - 04:19 PM
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Here's an eBay link for 10 DIN5 jacks for about $4 USD: https://www.ebay.com/itm/10Pcs-Set-PCB-Panel-Mounts-Female-Connector-DIN5-DIN-5Pin-Jack-DS-5-01-MIDI/133484197531?hash=item1f1447369b:g:~YAAAOSwU59fKTsx

 

You can use the H11L1 opto-isolator for the 6N138.  The H11L1 closely resembles the PC900 original spec MIDI opto-isolator.

 

You can get the Arduino MIDI shield for about $7.  This has three DIN5 (in, out, thru) and one opto-iso.

 

I have found that the best home-brew MIDI combination is two inputs and one output.  With this config, one AVR MIDI in goes to the MIDI OUT of the tone module, and the other MIDI IN goes to MIDI piano keyboard.  The editor software on the AVR can send the command to download all the current voice data from the synth using MIDI OUT and receive all that incoming input data on one of the MIDI IN.  The voice params can be displayed on a TFT screen and/or edited.  The MIDI OUT also sends note-on data to the synth as well as sys-ex requests.

 

With an Arduino and other bootloaders, it is necessary to block the MIDI input from the keyboard and the tone module when the AVR flash is being updated with a new program.   The keyboard is sending Active Sense bytes [0xFE] every 300 mS, and they interfere with the bootloader's input data.

 

When using a DIY MIDI interface with a +3.3V CPU, use a 150 ohm resistor on the MIDI OUT instead of 220 ohms.  This will supply enough current on MIDI OUT to fully saturate the photo-resistor in the opto-isolator of the MIDI-IN on the other end.

Last Edited: Wed. Sep 9, 2020 - 04:26 PM
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Kartman
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Posted by Kartman: Wed. Sep 9, 2020 - 09:28 PM
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The cheapy casio type keyboards have had midi for years. See if you can pick up a secondhand or dud one for nix and gut it for the goodies you want. A friend fixes these things and he would have a pile of boards with the required bits, but unfortunately I’m further away from you than china.

Check out thrift shops or the local fix it man.

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Plexd
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Posted by Plexd: Thu. Sep 10, 2020 - 12:26 AM
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The MitXela dot com website has info on midi if you dig, a cool converter of midi tunes to a six voice player, a converter for Chan's MG Wave table music generator ... but as far as hardware pricing... it's (IMO) not worth the cash.  To be fair, I'm cheap, I've built my last 3 programmers... so I'm probably not the best person to ask.

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Gold Markclawson
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Posted by clawson: Thu. Sep 10, 2020 - 08:56 AM
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I'm just going to given in and buy the bits anyway. Life is too short. (and the current impact of that phrase just hit home as I typed it!)

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jgmdesign
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Posted by jgmdesign: Fri. Sep 11, 2020 - 12:27 PM
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Please mark a solution if one has been had devil

 

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Gold Markclawson
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Posted by clawson: Fri. Sep 11, 2020 - 03:49 PM
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Not solved as yet. I'm still waiting to see if there are other options.

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mha11
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Posted by mha11: Sat. Sep 12, 2020 - 04:05 PM
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I looked at OSH Park, hoping to find something for you, but nothing jumped out. I have bought MIDI boards from vendors on Tindie, but they're sold out now.

 

But, be careful with the 6N138 -- many designs leave out the pull-down resistor on pin 7, which makes for a slow rising edge at the open collector output. From looking at a few schematics of commercial gear, none use the 6N138. Opinion: it was used by hobbyists at some point, and is now ingrained, even though it's not a good opto-isolator for this use.

 

Have fun!

Mike

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Gold Markclawson
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Posted by clawson: Sat. Sep 12, 2020 - 06:58 PM
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It's actually to connect to a Teensy 4 (600MHz of embedded loveliness!) so I'm pretty much just going to go with what Paul from PJRC recommends in reference designs ( https://www.pjrc.com/teensy/td_libs_MIDI.html) . Having said that I have ordered a "backup" from one of the Chinese suppliers on ebay so I might just patiently await that (and use USB MIDI until then)

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