So Many Questions... mux... encoders... OSC

Hello There,
I have 2 zynthians, one 3B and 5" GIPO screen one 3B+ and HDMI 7" screen, encoders connected directly to the GPIO pins and working fine…
Here’s a little fun jam I did with the 3B+ (which also have embedded battery cell, amp+speaker) for last weekend Hardware Jam Challenge (a group on FB) which topic was 007. Execution is not perfect but the ZynSeq is really a great addition and makes it easier to play .

So far so good… but I just ordered a zynaptic 2 to get my Zynthian synced in MIDI to my other gear and maybe send/receive CV/gate. I found out I will certainly lack some GPIO pin to plug all encoders (and what about a sound card or the 5 inch screen ?) .

Should I install another MCP23017 ? Did anybody tried to use some 74hc4067 multiplexers ?
I also would like to add a couple of extra buttons to access the sequencer and extra encoders to have some functions accessible instantly.

I have been tempted by the zynscreen but was afraid of the screen size, drawing notes on a 7" screen is already a bit tricky, on the 5" I have to use a needle so I guess it must be done with the encoders on a 3,5".

Also is there some way to implement OPEN STAGE CONTROL ? This is the ultimate tool to make an OSC modular MIDI controller.

Thanks a lot anyway for making this box real, it is fun and powerful.
Have a nice day


Oh and Ableton Link would be nice… is there something in the pipe ?

Nice box you built there!

I’m trying to build something similar. Could you help me sharing some photos of the inside and the components you used?

Hi @b_a_t! Welcome to the community. That is a really nice bit of music - well done. I see you are suffering low voltage. You will want to improve your power supply / cabling to reduce the risk of clicks on output.

I won’t answer the MCP question - I think others may be better placed.

Using a stylus with ZynSeq on a 3.5" screen works okay although sometimes the screen membrane is so loose that it results in bad registration with is frustrating. I think I find the stylus and small screen a bit easier than finger and larger screen but would prefer to use the larger screen, especially if I could use a stylus. I don’t have a suitable stylus for my 7" capacative screen.

OSC is already implemented. It remains a work in progress but you can already do many things with it. Check out the wiki.

I am not aware of any work on implementing Ableton Link. I haven’t looked into it before but see it is available on GitHub. If you add a feature request with some good use cases then maybe someone might pick up the batton.

here you are, not my proudest build tho ! Sorry for the long reply but I didn’t want to open it while I didn’t have to, now I have received the Zynaptic 2 board, I’m redesigning the whole thing on a proto-board… building some kind of hat for the R-Pi! And here is a screenshot of the wiring config. Capture d’écran 2021-06-11 à 10.51.26|690x313


Thank you! I really appreciate this. You must be proud, the best build is the one that actually gets done and enjoyed :smile:

Hi @b_a_t !!

Congratulations for your little session. I really enjoyed the jam!!

Regarding your question:

If you already ordered a zynaptik2, it include a MCP23017 with 16 extra GPIO pins that you can use for “gate” input/output or assign to custom switches.

FYI, i’m studying the best way of integrating Open Stage Control on zynthian. It would be a nice and very useful add.

Best Regards,

BTW, i just added your nice video to the wiki’s Sound Demos:

Thanks for sharing!

This was discussed at last zynthclub (notes to follow). It looked interesting. I would like to do some benchmarking to check the overhead.

Tx everyone for your kind words !
So glad to know you guys are looking towards OpenStageControl (@riban told me about OSC in his first reply but I did not insist on STAGE…) I did open the feature request about Ableton link and I look forward being able to jam with other zynthianners (is it zynthianists ?) without sync cable…
Actually I could open this one box since I am “accidentally” building the second one (as the first was the test to see if Zynthian OS could fit my setup)… Won’t fit in the OZINE club or will give this version to a friend !).
The hat is almost done and I just found a nice external hard drive enclosure in the defect units at work so the next Zynthian box will be nice outside and nice inside.
Still struggling to find a way for the box to work on DC plug when charging the battery without the current to flow back in the USB port and frying the power bank controller. I guess I’ll make some some basic tests with diodes… wish me luck.
Today on lunch break I plugged the MCP 23017… it took me a while to figure out the numbers (had to check the Zynaptic V2 schematic on github to be sure) but I soldered connections from the R-PI to the Zynaptic (just to the sockets eh !) as follow
SDA → SDA1 : pin 3 (wPI 8, GPIO 002)
SCL → SCL1 : pin 5 (wPI 9, GPIO 003)
INT A pin 36 → GPIO GEN 2 : pin 13 (wPI 2 ,GPIO 27)
INTA B pin 37 → GPIO_GCLK : pin 07 (wPI 7, GPIO004)
5V → 5V
3,3V → 3,3 V

Once I’ll have the faceplate cut for the screen and drilled holes for the encoders,
-I’ll also have to make those tiny tiny solders to plug the MIDI jack ports and test those DA/AD jack sockets,
-try to map buttons for a quick access to the sequencer a perhaps something like 60Knobs,
-plug in a soundcard (I made some tests with my second hand Behringer HD404 that seem to work out of the box when selected in Audio config even if i’m secretely looking for the Zynthian official Audio hat
-jam with those new functions until I test “something new” brick the device, consider I have no backup even it would have been really easy to do so before messing up, burn a new SD card, think of a new way to use the Zynthian box and start over

I’m so hyped by this zynthian thing because I’m really digging the less is more philosophy and this device / OS is really small yet versatile, so here I give you the MIDI mixer my zynthian is being used with

Oh and thanks for the low voltage tip ! I figured out plugging the power USB input to the second USB output port of the power bank fixed everything and I even have less Xruns.

You can get power banks that can be charged at same time as supplying so act like a UPS. You can also get dedicated 5V UPS. By supplying power via UPS you don’t need to worry about dual feeding or switching supply.

That’s more than I manage to keep going at any one time … :slight_smile:

Dares you to take that in your carryon for your next air trip :>

Don’t mention carrion in the presence of @wyleu!

1 Like

I don’t take the plane and the battery is easily removable… :sweat_smile:

Regarding your custom mixer/dedicated computer, do you have any blogpost or anything explaining the build? It seems to be quite the interesting device (i’m also wondering about the led encoders)

I do have a kind of build log on FB with the same name B_A_T, you can see the different shapes it has been through for the past 5 years… (among some other DIY audio thingies)
It’s basically a mixer or a DAW functioning with no keyboard nor mouse, it mainly runs Traktor as 4 buses with full control (EQ-loops-FX-sampling-remix decks-stems decks-track decks) but each bus can also be maschine or Ableton outputs (which are running aside Traktor with ableton link), so it can also send or receive a master clock or MIDI events, and it has (for now) 8 INs and 8 OUTs. Teensy 3.2 to handle extra buttons and Innofader (really smooth and sharp for scratching).
It’s a MBPro 13" logic board with a MBPro 15" battery so it can run 4-5 hours on battery with all Ableton, Maschine, VCV RACK, Traktor2 and Traktor3 running.
I cannot be creative when trying to make music on a PC so this wa the alternative, the biggest part was designing an interface that could be easily remebered based on 16 encoders with LED feedback (ring, detent and encoder switch with a whole lot of colors) and 6 buttons to manage 4 pages with Shift and Alt functions for each page.
A switch allows to change MIDI layer and screen display to the different apps.
I am mainly looking towards Zynthian since I think this would be the perfect tool for my setup : battery powered, will run smoothly 4 synths on different outputs using a second hand Behringer HD404 that will be routed inside Ableton and then inside a Traktor Live input deck (this allows to mix existing tracks with some live jamming, live remixing or sampling and get instant vinyl touch on live-recorded zynthian patterns… my main drum machine is a modified Volca Sample which is also routed inside my MIDI mixer…

some jams are also on Youtube, no clean track though… can’t wait to have my ZynthBox ready to jam