Minimum config possible?

[MukiEX]

I'm trying to build a tiny fightstick version (60mm buttons, 12x6.5" panel, slider w/ copper tape 'n 3 MPR121 breakout boards) and I think I'm doing something horrendously wrong as I piece things together.

I've got the slider wired up, but whether I plug in one MPR121 breakout board (the sparkfun one) or all 3, the device doesn't start up with SDA/SCL connected. Once I disconnect them it starts up and I see the joystick in the gamepads menu. If I plug in nothing (so bare board), the system starts up with both analog sticks stuttering in random directions.

Is there a minimum config to start with to make sure things are wired up correctly? Just like a few buttons or so.

[ravinrabbid]

Hi,

the firmware expects the MPR121s to always be there and if none of them are it will likely just read random values. That's where the flickering comes from. All other buttons should still function as normal in this case.

If you want to disable the slider completely, you could try to comment out lines 160 and 231 in main.cpp.
If you want to test with one MPR121 only, setting all three I2C addresses to the same value (i.e. the address of the MPR you want to check) in GlobalConfiguration.h line 67 could be worth a try.

Regarding the device not starting up, does that mean there is also no output on the OLED and the LEDs or is it just not recognized as a USB device? The former might hint to something being shorted in your wiring.

[MukiEX]

Ah, much appreciated! There's also high likelihood I've also got the wrong addresses set on my other MPR121s (I have them at [no ADD set] / [ADD wired to SDA] / [ADD wired to SCL]) but I'll test 'em one at a time. =)

Regarding the device not starting up, does that mean there is also no output on the OLED and the LEDs or is it just not recognized as a USB device?

Ah, it's the latter. It's why I was trying to go with a single MPR121; I figured it was most likely I miswired something that was causing it not to show up as a device.

[ravinrabbid]

Hmm, those Sparkfun MPR121 boards look very similar to the no-name ones I used. If I remember correctly I also had some issues with setting the address at first because I didn't notice you had to cut the trace from ADDR to GND before connecting them to SCL/SCA. But maybe you already did :)

[MukiEX]

You know, I definitely ran an Xacto between ADD pads a few times, I should probably run a continuity check. I didn't even think about that 'til just now, I was trying to check the scratches with my phone cam's zoom mode.

I too have the Sparkfun MPR121 breakout bootleg, they discontinued the original and the PCB brd file is on Github, which I'm guessing drop shippers filled the gap on ^o^

[MukiEX]

I'M A NUMPTY!

I didn't realize you had to connect GND. I read the diagram too literally XD

[ravinrabbid]

Nice one! Glad you got it to work :D