UPDATE 2: It was indeed the TRS cable that was the issue. I just got my TRRS cable and it is now working fine.
UPDATE: I ithink I know the problem, I'll update this post after I confirm it in a few days. This is the cable I was using 
This isn't a TRRS cable this is a TRS cable and I dont have a random TRRS cable to try out. I will wait for a few days until my actual TRRS cable that I ordered reaches me.
Gotta preface this by saying this is my first ever keyboard build, and pretty much my first time soldering something involved.
But anyways, I got the left half working, even with my slightly shoddy soldering, and was feeling pretty confident. Finished off soldering the right half and checked for bridges with a multimeter and that looked fine.
I flashed the same firmware that I used on the left to the right half. And then connected them together and plugged in the usb on the left half. The left half was working as usual, but the right half didn't recognise any inputs. It showed the lily58 logo but that was all that was showing on the oled.
I disconnected the halves and connected only the right half, and all the keys were being detected as if it were the left half but mirrored to the right.
What have I done wrong?Gotta preface this by saying this is my first ever keyboard build, and pretty much my first time soldering something involved.
But anyways, I got the left half working, even with my slightly shoddy soldering, and was feeling pretty confident. Finished off soldering the right half and checked for bridges with a multimeter and that looked fine.
I flashed the same firmware that I used on the left to the right half. And then connected them together and plugged in the usb on the left half. The left half was working as usual, but the right half didn't recognise any inputs. It showed the lily58 logo but that was all that was showing on the oled.
I disconnected the halves and connected only the right half, and all the keys were being detected as if it were the left half but mirrored to the right.
What have I done wrong?
I'm using a splinky rp2040 for the MCU, I have ordered new cables but they won't arrive for a few more days, I am using an old headphone cable to connect the halves.
I'm not sure if this is true for the firmware you're using, but at least for zmk, the left and right halves use left and right side specific firmware files. It sounds you installed the left side firmware on both.
I'm using qmk and I didn't see anywhere in the guides that I had to use different firmware for both halves. It told me to use the same on both.
Makes sense. It's probably the trrs cable issue you mentioned. Hope it works after that!