How to specify I2C pins for promicro52840 ( Lili58 )? and how to not lose my mind

[prisma jewel]

I've built a split keyboard – the Lily58 with ZMK – and it works.

But the problem was with the OLED screens (SSD1306). To fix it, I found this: https://github.com/mctechnology17/zmk-nice-oled/tree/main
and it almost works.

One of the screens doesn’t show anything.

I thought it was the screen, but nope – I swapped them and both are good.

I thought the problem was with the pins on a specific side, but nope – I swapped chips and it worked.

So the last part I needed to check was one Pro Micro 52840.

It looks OK. I used a voltmeter to verify (continuity test) if I made a mistake with soldering, but nope.

I know, a lot of “nope.”

So my last assumption is that it’s either a problem with the controller or the firmware.

my config - https://github.com/Upskxkit/lily58-wireless-view-zmk-config

[night quiver]

The lily58's OLED pins are already established on the left half: https://github.com/Upskxkit/lily58-wireless-view-zmk-config/actions/runs/17690684131/job/50283455794#step:13:567
You've already enabled logging on the left side, so you can look for i2c-related error messages:

It is very likely you need to check again with the voltmeter. If you have a battery attached, you can't check continuity (resistance) unless you desolder/detach it. (If you aren't willing/able to remove it, you will have to measure the voltage on each display pin.)

[prisma jewel]

Thanks, I have a connector for the battery. I’ll try both cases.

[prisma jewel]

no problem on pins, I got this message
i2c_nrfx_twi: Error 0x0BAE0001 occurred for message
ssd1306: Failed to initialize device

[night quiver]

if the display wasn't being picked up at all, the error message would be a bit different: #1415250274041331782 message

...Perhaps you just [lost the supermini roulette](#hardware message). It sounds like you socketed (good foresight) so replacing it wouldn't be difficult.