Hi all,
I can imagine everyone’s busy right now with zynbleton and stuff. Maybe someone has capacities for this little issue:
I have lying around some parts with which I wanted to upgrade my custom made zynthian since a while. One of these are some capacitive buttons I planned to install underneath the wooden surface. Now tonight I thought I wanted to just loosely connect one of them for a proof of concept:
The working state of the machine was 4 encoders to 12 pins of an MCP23017 multiplexer. You can see on the photos what I tried: I connected the data pin of the button to a spare MCP pin and VCC and GND to spare corresponding pins directly on the Audio DAC (mirroring the PI’s GPIO), additionally I tried the setup with and without a 47nF ceramic cap to GND. Then I stated the correct pin number (115 here for the B7 MCP pinout) in the wiring setup:
########################## ----------------------------------------
# # ZynthianOS ORAM-2505
# ## # Timestamp: 2025-05-30
# ## # # ## # Built from RaspberryPiOS Bookworm (aarch64)
# # # # # # # # ----------------------------------------
### # # # # # # ### Kit: Custom
# # # # # # # # # # Display: Generic HDMI/DSI Display
# ## # # # # ## # Soundcard: HifiBerry DAC+ ADC PRO
# ## ## # Wiring Layout: MCP23017_ENCODERS_V5TOUCH
# # ----------------------------------------
##########################
zynthian-ui: vangelis (4ce678)
zynthian-webconf: vangelis (0e2c25)
zyncoder: vangelis (dbc512)
zynthian-sys: vangelis (8e9180)
zynthian-data: vangelis (b358f8)
---------------------------------------
Linux hannes-zynthian 6.12.47+rpt-rpi-2712 #1 SMP PREEMPT Debian 1:6.12.47-1+rpt 1~bookworm (2025-09-16) aarch64
# Zynthian Wiring Config
export ZYNTHIAN_WIRING_LAYOUT="MCP23017_ENCODERS_V5TOUCH"
export ZYNTHIAN_WIRING_ENCODER_A="112,108,104,100"
export ZYNTHIAN_WIRING_ENCODER_B="113,109,105,101"
export ZYNTHIAN_WIRING_SWITCHES="115,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,114,110,106,102"
export ZYNTHIAN_WIRING_MCP23017_I2C_ADDRESS="0x20"
export ZYNTHIAN_WIRING_MCP23017_INTA_PIN="27"
export ZYNTHIAN_WIRING_MCP23017_INTB_PIN="25"
Result:
- On touch the control light on the back of the button lights up
- Short press shows results on the UI, sometimes, but not always the expected one. I chose the OPT/ADMIN button for the experiment and it sometimes enters the admin menu, sometimes the main menu and sometimes the snapshot saving menu
- long press (and I think also bold press) doens’t work at all
- On shutdown Miss Oram confronts me with a “SegFault” error and then reenters the UI instead of shutting down, in some cases it stays in the “saving snapshots” state forever. The error also persist after disconnecting every altered connections. (EDIT: The segfault error didn’t occure now after removing all the chains before shutdown)
I mean, I didn’t solder the connections, you can see on the pictures that I just winded some jumper cables around the connectors. Might be this is the problem, but I am not in the state of mind to finalize the concept with the soldering iron right now.
A question would also be if anyone of you has experience with these kind of capacitive buttons: must they be powered and how (I used 5V)? Should I use the debouncing cap?
Might someone have an idea about the issue?
