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

Duophonic keyboard? In keyboard mode, hold two X column buttons to select two tracks e.g. 1&5 (aka G1T1 and G2T1). Track 1 is controlled by the top 8 buttons, track 5 by the bottom. Damn, I'm not sure how the transpose works then!

Congrats on the build if all is well! You need to first burn a virgin PIC with the MIOS bootloader. After you can send it regular MIDI data using MIOS Studio. The easiest way is with a normal 8-bit Core because it has standard MIDI ports. The update is possible if you have your SEQ ready to go with the DIN cable and everything, just configure the router page using e.g. USB2->MIDI3 and MIDI3->USB2. Select USB2 as the MIDI in and out on MIOS Studio and you're talking to the Core8!

Lifetime is given as 500k cycles to retain contact resistance (<100mOhm increase) and operating force (+/-30%).

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.

The last lot of samples cost me $150 to ship... so I have not yet tested the action. This one has an operating force of 180±50gf and a switch travel of 0.2±0.1mm. So very much like the standard SEQ switches.

I will soon be ordering some custom parts and I thought it might be a good opportunity to get some special switches at the same time. This is an RGB tact switch with a common anode. The key specs are: Brightness (RGB) 320, 300, 110 mcd, so similar to the LEDs used in the BLM. Viewing angle: 120 degrees. Lead spacing: 4.5*6.5mm Cap dimensions: 7.8*7.8mm Pricing is not fixed yet but could be around 2-2.50 USD per piece. Please indicate any quantities that you would like. It's not a commitment to buy, it just gives me some idea during the order process.

Suggested spacing for the 4x4 encoder bank: 30mm horizontal 25.33mm vertical. This should fit on a 100x120mm PCB (3U friendly). Or is it a bit tight?

Hi George, You want to wire SO (serial output) from the Core to SI (serial input) on the AOUT_NG. The top row of J19 is: Vs Vd SO SC RC1 0V, 5V, serial out, serial clock, chip select 1. J1 on AOUT_NG is: Vs Vd CS SI SC 0V, 5V, chip select, serial input, serial clock. You can see how the chip select jumps into the middle and pushes SI and SC over. So wiring up an IDC like I showed is one way around this mismatch. You could still use this cable with the line driver board ignoring the JAOUT header.

2*Core8 running MBCV. 2*AOUT_NG for 16 CV. 5V gates come from Core J5 I think. MIDI out1 to MIDI in2. Should be able to set up a MIDI merge.

Good to know! I'm obviously not using the line driver boards.

Easiest way to do it quick. Here the black wire is pin 1, brown is pin 5 6 but the right-most. This cable is 1:1 on the Core, probably simplest to wire the line driver straight and yoga after. The top row relative to the guide nub contains the serial output (SO) and so should connect to the AOUT data header.

Have you tried connecting the AOUT_NG directly to the Core? Keep in mind the non-standard pinning! that the pinning is not 1:1.

That's really nice of them to give you the circuit diagram! I had a look too, I think the reset pulse is only generated on power up once the input voltage is stable and the zener diode starts to conduct. So fiddling with U20 is the correct way IMO.

Any further thoughts? Is the concept workable/what people want in MIDIbox CV? I think at this stage it will be a good idea to create several small PCBs, that way the component heights are not so critical and it's more flexible (can even be used in other MIDIbox projects). I've also looked at getting RGB tact switches. The tricky part is still the OLEDs, I want to get them very close together which is difficult with the breakout boards. More expensive too. Soldering the 0.7mm ribbon is known to be troublesome but I'll try to find a way.

Okay, I have the encoders and a 5050 WS2812 LED to test. The problems is that the LED is around 1.65mm tall but the clearance underneath the encoder is only ~1.1mm. There are a few ways around this. First, you could solder the encoder in "proud" i.e. raised up above the LED. The neatest way would be to rest the PCB flat against a work surface, insert the encoder and solder from the top. There's a slight risk that your encoder doesn't go in straight. Second is to use a washer as a spacer. Nylon is best for non-conductivity. Trouble is there are no washers of the right size. M5 is good on the outside (10mm) but too narrow inside (~5.5mm). M6 is just too small inside, M7 doesn't exist and M8 is far too wide on the outside. We need a washer with 7.5-8mm ID and 10-11mm OD. 2mm thick is best, but 2*1mm would also work. I tried to drill some M5 washers to 7.5mm but the bit chewed up the plastic. I also looked at imperial sizes, 5/16" is fine but 1/2" OD is too much. An O-ring would at least be thin enough but to get the right height you need 2mm cross section/thickness (stacking them would be difficult). So then we have 7.5mm ID and 11.5mm OD which might just work. I also worry about the lifetime of rubber products. Lastly one could get pieces of 2mm acrylic laser cut; they could even be square to save on machine time. I wonder about the expense of this though. So, that's where I'm at at the moment, if you have any ideas please feel free to share.

Waitlist: taximan (PCB+Case)

Did you try to configure the port as AOUTX as opposed to a MIDI or USB channel?

Thanks, I added it.

Notice I recommend 10k for the LED resistors, hopefully you can change them. For the covers, perhaps some sort of silicone block or tube could be used, I had a look at the hardware store this week but didn't find anything. Or unmelted hotmelt glue sticks? I don't quite understand; only two circular "washers" should be needed (right-most top and bottom viewing from the PCB front) as the remaining PCB area is covered by the spacer?

Great work! Which company made it? Did you do the infill yourself?

Okay, thanks for the file, let's see how yours goes and I can add it to the OP. I didn't have issues with mine (corners are properly rounded) and I think TK.s was also good? In any case, the spacer holes are a few mm larger than the buttons.

Yes, it should work from J11E. Or if you connect a MIDI IO board, you could for instance take MIDI IO4 from J2.

Thanks for the kind words! It's very satisfying to see everything come together after countless hours of design, component sourcing and dealing with many different companies.

TK.: very nice! It looks like the slider implementation is very good. I guess you kept the longer sliders in? This will be a personal preference I suppose. An idea I had was to make or buy some silicone covers to use as slider caps. This might make them a bit more ergonomic and also act as diffusers for the LEDs which can be quite bright. I take it that there's no issues with the case? Stability (i.e. no PCB flex) is good with the extra standoffs? Are all M2 grub screws installed? Do the bottom feet work? Next up will be to connect up extra expression pedals, CV inputs etc. :) (another DIN connector?) The BLM/quad IIC schematic always gives me a headache :). My approach was to harvest old PC cables (with single or dual female pin sockets, could also crimp new ones) that connected all of the front switches, LEDs etc. to the motherboard, and join them with an IDC10. I'm still using the F1 Core, but luckily I have a breakout board which also separates MIDI IO 3. If you have an older Core8 you can always swap out this for the miniCore during testing, just use temporary clips on the MIDI outs. You need to supply power to the BLM, and please don't send data without the main board powered up.