What do you guys use for your custom keyboards as the controller?

[Shroomster]

I am in the planning process of building a 40 or 60% keyboard from a keyboard I got for cheap with MX Blacks. I'm thinking of using either a teensy or a controller I ripped out of an membrane keyboard and the pins have been mapped already. Which should I use. I already have the membrane controller or should I buy a Teensy or another alternative?

[Yoe]

With the Teensy you have the freedom to wire the matrix any way you want it, and to configure function layers which are a must if you make a 40% keyboard and more or less half the point of making custom keyboards imho. If you're making a 40% keyboard you could probably get away with using the cheaper Pro Micro instead of the Teensy 2.0 and still use the TMK firmware, but it's a bit more difficult to reprogram.

[Findecanor]

With the membrane keyboard's controller you will be restricted to using its matrix and you won't be able to get N-key rollover.
If you don't need N-key rollover you could perhaps reuse the PCB of the mechanical keyboard you have, by creating a matrix out of the printed leads still on the PCB.

[Shroomster]

With the Teensy you have the freedom to wire the matrix any way you want it, and to configure function layers which are a must if you make a 40% keyboard and more or less half the point of making custom keyboards imho. If you're making a 40% keyboard you could probably get away with using the cheaper Pro Micro instead of the Teensy 2.0 and still use the TMK firmware, but it's a bit more difficult to reprogram.

With the membrane keyboard's controller you will be restricted to using its matrix and you won't be able to get N-key rollover.
If you don't need N-key rollover you could perhaps reuse the PCB of the mechanical keyboard you have, by creating a matrix out of the printed leads still on the PCB.

Thanks for the help. I shall get a Teensy in that case, as the mechanical's PCB is busted according to the seller.

[CPTBadAss]

+1 for the Teensy