QMK Matrix Scanning Decade Counters

[Tuggi]

Hello, GeekHack!

This is my first post, so please bear with me. I'm currently in the midsts of developing a drop-in replacement controller for the Focus FK-5001, in the form of a board that sockets in place of the Intel chip already present on the focus, and takes over control of the matrix and display with QMK. Because of IO concerns, I'd like to use decade/johnson counters to drive the columns of the matrix and read the rows to save pins. Will QMK provide a way to use counters instead of direct interface with the matrix? I'm honestly still on the fence about what to use in the way of a controller. For all past projects, I've used the trusty 32u4, but I'm considering using a teensy 2.5 for it's great IO and vastly more powerful MCU, I do plan on driving an LCD/OLED in place of the calculator after all. Thank you guys in advance for any advice. Please forgive me if this is a bit of a weird ask.

[suicidal_orange]

This is a weird ask, nothing wrong with it but as no-one has seen the need to use them before it suggests to me you don't need to either

What are the IO concerns, is it a huge matrix with lots of gaps?  The Teensy 2.0++ is usually the first stop when you need more pins as it's fully supported in all firmwares.

[Tuggi]

This is a weird ask, nothing wrong with it but as no-one has seen the need to use them before it suggests to me you don't need to either

What are the IO concerns, is it a huge matrix with lots of gaps?  The Teensy 2.0++ is usually the first stop when you need more pins as it's fully supported in all firmwares.

Thanks for the response. Yeah, after sitting on it for a night, I suspect this might be a classic XY problem -- wanting to use counters instead of finding a proper MCU/matrix layout. I think my IO concerns were me being stubborn and wanting to stick with the 32u4 so I could integrate the MCU into the PCB instead of socketing a teensy, but teensy does seem like the proper route.

[suicidal_orange]

You could always use the chip that's on the Teensy 2.0++ directly on your board, should be easy enough to change the bootloader size in the firmware.  I want to say there's a 120% PCB that used one, would be much easier to find if I could think of it's name...