Entry 165

The analog stick's dead zone and reach

2026-10-161minput

Filescrates/rugrats/src/input.rs

The analog stick's bytes now become axes as the original's do. 0x8001a888 updates the twelve axis objects at 0x800cdac0 each frame; an analog one (type 2) takes its byte less 127, lets 24 either side of the middle count for nothing, scales what is left back to the whole 127 (x 127 x 0x13e22cbd >> 35, about 1.233), then to 4096 (x 4096 / 127) and clamps. The port had taken (byte - 128) x 32, with no dead zone, so a stick at rest drifting a few counts walked the body, and full travel was 4064 one way. stick_axis is the original's sum; its test checks the dead zone and both ends.

The digital axes (type 4, two buttons) were read on the way: one button gives -127 or +128, both or neither 127 (the middle), then the same scale, so the D-pad is +-4096 on its axis, as the port has it (worklog 164's open question on the analog scale is this one).

Still unknown: nothing