SuzoHapp Trackball Fix for Linux

fix_trackball.py

# SuzoHapp Trackball Fix
# v0.1 - 11/09/2021
# https://bentumbleson.com
#
# Requires python-evdev: https://python-evdev.readthedocs.io/en/latest/
#
# This script will constantly read the input from your SuzoHapp trackball
# and automatically inject a theoretical large relative movement into to system when
# a large rotation (determined by acceleration) of the trackball is detected.
#
# This works because when the analog trackball spins too quickly, the sensor
# will either read "0" because it's moving too fast, nothing at all, or a very
# low number which is not representative of the actual speed of the trackball.
#
# In MAME games like Golden Tee (gtfore06), we have to inject movement before
# any of the 0's or small numbers can register, or else your swing in the game in
# the game will sputter, leading to undesired results. This is why the script doesn't
# listen for unexpected "drops" in relative movement, and rather needs to proactively
# attempt to determine when a drop is likely to happen so it can correct beforehand.
#
# Thus, an arbitary measure of acceleration is calculated between each instance of
# a relative movement by the trackball, and if it is less than -100k, then a relative
# action is pushed to the system ten times, each 0.08 seconds after another.

from evdev import InputDevice, InputEvent, list_devices, ecodes as e
import datetime
import time

devices = [InputDevice(path) for path in list_devices()]

for device in devices:
    if device.name == "HID 1241:1111":  # this is the name of your SuzoHapp Trackball - replace as needed!
        # set dev equal to the matched device
        dev = InputDevice(device.path)

# display the device name to start
print(dev)

# this method is used to send a simulated value to the computer
def pushValue(value):
    repeatCount = 10 # replace with whatever you need, I found 10 was needed in many cases
    for _ in range(repeatCount):
        # pass the value as a relative Y movement
        dev.write(e.EV_REL, e.REL_Y, value)
        # sync
        dev.write(e.EV_SYN, 0, 0)
        # sleep equivilant to 120hz
        time.sleep(0.008)


# we need to build up the current time so we can set define `last` before the loop starts for the first time
# this is messy and there's probably a better way to do this?
dt = datetime.datetime.now().timestamp()
sec = int(dt)
usec = int(str(dt - int(dt)).split(".")[1])
last = InputEvent(sec, usec, e.EV_REL, e.REL_Y, 0)

# process each movement of the trackball
for event in dev.read_loop():
    # 2 = Relative Movement, we only want these
    if event.type == 2:
        # event.code of 1 = REL_Y (relative Y, since we aren't interested in x movements)
        if event.code == 1:
            # calculate the different of relative movement values between the last event of this type
            diffValue = abs(event.value - (last.value or 0))
            # calculate acceleration
            diffInTimestampsSquared = (event.timestamp() - last.timestamp()) ** 2
            if diffInTimestampsSquared == 0:
                accel = 0
            else:
                accel = (event.value - last.value) / (diffInTimestampsSquared)

            # uncomment to test acceleration calculation based on values
            print(accel, " ---- ", event.value, last.value, (event.timestamp() - last.timestamp()))

            # negative acceleration is forward movement, 100k
            if accel < -100000:
                pushValue(-35) # -35 is the equivialant of smacking the trackball quite hard

            # set the current event to the last so we can compare to it on the next event
            last = event