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Story of a keyboard-build


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Hey people,

in this thread I'll post time after time updates about my latest keyboard build. Also I'll use this thread to publish eagle-PCB-layout-files and schematics. But please be patient. Uploading and documenting all that stuff is highly time consuming and it's right before christmas.

So far everything works great, but the work under the hood was really time consuming because I used a lot of modules... some available from Tim, some I did on my own. I think modules are great if you need high flexibility... and all the modules are working perfectly. But if it comes down to save space and wiring, modules are a mess. Anyway... here we go:

So I was tired using a laptop, a soundcard, tons of cables and all that stuff on stage. So I thought: What if I put the computer into the keyboard? It was quite successful. I used an Mini-ITX mainboard from Gigabyte, an i5-3570k (I'd go with a better i7 if I hadn't had that i5 before) with a low profile cooler. The mainboard is equipped with 16GB of RAM. Also I integrated two Samsung SSDs with 500GB each. The whole thing is powered through a Seasonic SS250U power supply. 
As soundcard I use a PCIe card from RME HDSPe AiO. Because this only has two audio in/outs, I also bought two expansion-board that gives me another four in and outs. The first two analog-outs are going through a self-made DI-box with high quality LEHLE-transformer... absolutely great stuff. This DI-box features also a 20dB PAD and a GND-lift. 

Let's hand over to the MIDIbox-side:
I use two cores. One of them only takes care of the keyboard scanning. It was very important to me to not make a compromise on this. This core is connected via MIDI-out to the MIDI-In of the other core. Both cores are STM32F4 based. I used my own PCBs for that. @TK. Is it a problem if I publish those schematics and layouts for the core? I know that the official core is not published yet to cover the costs for PCB production and development. The PCB I developed only contains the connectors I need: it has J8/9, J19, J10A, J11 and J30 (as far as I remember... don't have it right in front of me at the moment). I tried to get a smaller footprint of the whole PCB. It also features a MicroSD-card slot instead of the SD-card-slot in the official PCB.

My keyboard has nine analog faders build in... they are not motorized. I don't need that for now as they are much more expensive and also take more space. Also they are more difficult to wire up and connect. At first I did some tests with the AINSER8. But after a while I gave AINSER64 a try with the result, that it has less jitter than the AINSER8. The faders are a lot more quiet than with AINSER8. As I needed more than 16 analog inputs this was needed anyway. I power the AINSER64 through the core and the core receives it's power directly from the seasonic-power supply and NOT via USB.

I needed some LEDs to visualize the status of my faders. A long long time ago I wanted to start another LED-fader-project but never finished it. So I had a lot of those LED-bars laying around... I took them and putted them into the board... works and feels great! On the next revision I'd try to use one big PCB for all 9 LED-bars to safe wiring and time for mounting. Now I used two 10pin IDC connectors (with only 8 pins of each are connected to the LED-bars = 16 LEDs). I did some mistakes when assembling the LED-PCBs... now sometimes some LEDs don't work... anyway... I can live with that for now.
@TK. How about the WS2812 or APA102-LEDs? Do you think it's worth using them as LED-rings? I'm not sure what the status is and if they are supported in that way by MIDIbox. Would be a great alternative but they take a lot more space than 0603 SMD LEDs of course.

The LED-bars are connected to small modules I did based on @novski designs. Those small modules are equipped with one or two DIN / DOUT modules. They work great and the advantage is, that I can stack them directly on the pinheader of the PCB... no cables needed! A bit hotglue and you are ready to go.

I also have 8 encoders on each side of the keyboard. The right side is not connected yet... not sure if I do need so many encoders ;-) Of course they are also equipped with LED-rings. While the LED-bars where assembled by factory (I think I used SEEED) the encoder-rings came blank... so it took me a looooooong time adding 128 0805 SMD LEDs to all PCBs... at this time I had not have my reflow-oven... with this one that might be an easy task :-)
The encoders (and the switches of the encoders) are connected to a 4xDIN board from novski. I'm not sure if this board really works well. Sometimes if I set debug on, MIOS lists tons of EVENT_BUTTONS. I'll need to investigate that. Maybe it has something to do with RC1 / RC2 lines.

Underneath the faders I have a set of 2x8 buttons. I'm not really happy with them. I did the caps by myself and this was a really shitty work... next time I will use tact-switches that already come with caps f.e. TC011 like I did in the 1x8 button-row right in front of the player / underneath the display.
For the buttons I designed a DIO-breakout-board. This breakout-board splits the matrix configuration of the 2x8 pinheader of the DIO-module to a more usable 2x5pin header-configuration with the row on pin 1 and the switch-lines on 3-10. With this way it's very easy to connect tons of buttons to a MIDIbox. . Same for the LEDs of the buttons. I used a DOUT-module with ULN2803 as LED driver (btw. I drive all LEDs with ULN2803 and do NOT use a resistor before or after the LEDs. As those LED-lines are scanned, a limiting resistor doesn't seem to be necessary). 

That's mainly it... the keyboard has two MIDI I/Os on the back as well as four pedal connectors for two switches and two expression pedals. 

The touchscreen in the middle is a 10" capacitive screen... that works awesome!!

That's the story for now... like I said I'll try to keep this thread alive and add the PCB layouts and schematics later on.

Thanks for reading!!


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  • 4 months later...

I hope that it's okay that I unearth this thread because I think it's wonderful.  It's easily the best looking DIY integrated workstation rig I've seen built.

I have a question about the keybed because I didn't see it mentioned. Is that a Fatar TP/40 of some kind (ie. TP/40L, GH, etc.), or is it a TP/8Piano?  Also, where did you purchase it (ie. Doepfer) or was it salvaged from another controller/synth/digital piano?  Thanks and keep up the good work. :)

Edited by RagnarX
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  • 1 month later...

Thanks for the reply.  I imagine it would be a difficult prospect.  I have a story about how I acquired, and subsequently lost, my Fatar keybed.  I have a controller project that's been in the planning stages for several years, and I've only been able to acquire little bits for it here and there as I can afford them.  It's a little similar to what you've been able to build, but I haven't even really "broken ground" on mine yet.  A year ago, I was able to find a source on a TP/40L 88 keybed.  The way it was handled was I purchased it through a retailer, and the importer/distributor would ship it directly to me.  When I received it, the left end had been completely destroyed.  The keybed had been improperly packed (no padding AT ALL on the ends) and was likely dropped.  I was brokenhearted.  Even the nylon shipping brace that Fatar puts on both ends to stabilize the keybed had been shattered.  I have a couple of photos below.





I was able to return it with a UPS claim, but the distributor refused to take responsibility for improper packing.  They claimed that they did nothing improper, while UPS' claims office (and common sense) said otherwise.  The distributor told the retailer I bought it from that the only way they'd ship a new one to me was on a pallet and boat it to me (I live in Alaska, so shipping is a little less convenient than in the rest of the US).  There was also a hefty upcharge in shipping.  Based on this experience I had no faith they'd pack it properly this time either, so I declined.  Once they become available Stateside again I'm just going to buy a Studiologic SL88 Grand (TP/40 WOOD triple sensor on that one) and get creative with that, then use the Midibox NG platform with the rest of the controllers.

I hope I didn't derail your thread too much.  I appreciate you taking time to answer my questions. :cheers:

Edited by RagnarX
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