V5-kit - Available GPIOs?

Hello there,

In a vanilla V5-kit setup : is there any GPIO still available for generic use on the Pi 4 ? It’s for a basic sustain pedal.

FYI : I already have about 9 (DIY) switches at my feet all connected with yet another raspberry pi but I want only this switch (pedal) to be added directly on the Zynthian. How do I do what needs to be done‽

BTW (OffTopic) : I’ve done my 94th show with the Zynthian and boy am I a happy camper. I cannot wait to post sort of a setup demonstration hopefully sooner than later…

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Hi @PeterLuck !

The V5 expose 2 free RBPi GPIO in the control board’s EXT connector. First V5 have the connector soldered and recent V5.1 don’t, but soldering is trivial. It’s a 6-pin thru hole JST connector. The connector also include 5V, GND and I2c pins, so you could add up to 2 extra MCP23017 chips (2x16 GPIO).

If you want to use one of this RBPi GPIO for a switch pedal, let me know and i will modify.the wiring layout to allow this use. It should be trivial

The best

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What kind of JST connector? (There’s thousands of them)

Congratulations! The hundredth not far away then? Any insights or observations?

If the connector is not already soldered to the PCB then you can chose any 0.1" pitch connector to use. If it is already soldered then you can look at what is there.

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I2c you say. That got me thinking.

This is the last iteration of my setup :

I’m in the process of totally revamping it mainly moving from this 24"x12" pedal board to a 24"x16". The raspberry pi (on the top right) hosts most of my setup (SuperCollider based) with all GPIO plugged directly into it. This pi will be replaced by a tiny (yet bigger) industrial computer with only 8 GPIO inside when I currently need 12. Anywho, the setup should look like this :

The idea of endowing the Zynthian with 16 GPIO directly inside is quite the dream. I would then need for the Zyn to have a GPIO → OSC service which should be trivial to implement. (I’m assuming the Zynthian to be of the systemd persuasion (am-I right ?)).

Thanks a lot @jofemodo !

Zynthian is indeed of the “systemd persuasion”.
https://wiki.zynthian.org/index.php/Zynthian_SystemD_Startup

For reference :

I’ve yet to fiddle around with the Zynthian as I prefer to leave it intact. Besides, the Zynthian is way too pretty for me to disfigure it. My fat fingers lack either the gentle or delicate cycle. For now I’ve only done my shenanigans with my own DIY stuff. But with that being said : I’m up for a little slit in the front for [VCC, GND, SCL, SDA] . :smiley:

I’ll probably use a PCF8575 because that’s what I’ve found in my IC-mishmash box (it’s a 16 GPIO→I2C). I would install it not inside the Zyn itself but rather inside this franken-GPIO-box :


^ BTW, this box also hosts a 4 channel stereo mixer that outputs in a headphone amplifier for my in-ears (mainly for the click). Highlighted in green : the four channel-level potentiometers (no master).

I’ll report the evolution :slight_smile:

The V5 already has a slot cutout in the front upright to allow a flat cable to be fed to this connector.

Yes ! I completely forgot about that. I saw it when assembling it. You guys are the best !

I tried to characterize the interior of the female connector which should correspond to the male connector specifications. 15mm wide × 4mm high. There is 2.54mm between each pin and there are 6 of them.

It corresponds to a JST XH 2.54

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Exactly. JST XH 2.5mm, 6pin

Thank you for letting us know :heart:

But but but, what is the pinout ?

My tester reported (from left to right facing an assembled Zynthian) :
[GND, GPIO24, GPIO23, SCL, SDA, 5VDC]
This sounds about right to me so I’ll continue.

Yes, I would like to use one (either 23 or 24) for a switch triggering CC:64. I’m not sure what you mean by :

Oh, I suppose you’re talking about adding the two GPIO in the /hw-wiring page right ?

More or less :wink:
It’s slighty complex. I’ve to think about it

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I see. So then what could be the path from the rpi4 GPIO23 to CC:64 ? I could whip a standalone script to send midi.

I just commited the needed changes. Update in vangelis and access webconf wiring layout to configure the 2 extra GPIOs.

Note that i didn’t test with a real zynthian V5, but it should work … or not :grin:

Enjoy!

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This is for future reference:

It’s a top view from the V5 control board EXT-1 connector. I mean, this is how wires go out straight from the V5 case when using the front-side slot.

  • int7 is connected to RBPi GPIO 24 (wiring pi 5) => Zynthian Switch 25
  • int6 is connected to RBPi GPIO 23 (wiring pi 4) => Zynthian Switch 26

These pins are configured as pull-up, so they are “ON” when connected to GND and “OFF” when not connected.

The action for these 2 pins can be configured from webconf’s wiring layout. They are the 2 last zynswitches in the list.

It should be better explained in wiki, of course :wink:

Regards,

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