Scope of testing and known issues

A project log for Physical Keyboard for any Android phone

This is my attempt at having an android phone of my choice coupled to a portrait Physical QWERTY keyboard off an old blackberry.

kylemontikylemonti 11/10/2019 at 15:070 Comments

In its current test-phase, the complete phone and keyboard assy are rather bulky (more precisely it's just too long to fit in any reasonable pocket). Also, the weight on the phone means the whole thing is a bit top heavy and makes typing on it a bit less comfortable. This has been forseen which is why in the final build (the slider) I intend to pull the battery out of the phone and stick the battery right behind the keyboard and then attach a flexible extension cable to the motherboard which allows power to be delivered via the slider mechanism together with D+ and D- cables from the SK5126 chip. The battery connector seems to be a Hirose BM25, which I cannot find from the same shop I bought the BM 14B connector. This is my next task as it is a showstopper until I'm able to provide power to the phone of course.

Another annoying issue comes from the BM14B connector which adapts the keyboard's I/O. due to the extremely small pitch of 0.4mm between each solder, the SK5126 sometimes detects a small amount of voltage between 2 adjacent pins and registers this as a keypress. This problem has been largely mitigated by putting resistors in line with the rows, this also resolves any capacitative effect happening between these extremely close pins. Nonetheless it still manifests itself from time to time and I intend to keep a close eye on it during this test phase.