Fab4 Touchpad Notes

Tools - Using evtest and Settings->Advanced->Factory Test->Touchscreen

From a fab4 command prompt, you can run the follow command to trace raw touchpad values

evtest /dev/input/touchscreen0

The initial output of the command command explains a bit about what the values mean and shows max value for absolute x and y. Then as you touch the screen raw data will appear. It is handy to also have up the Touchscreen test applet (Settings->Advanced->Factory Test->Touchscreen) to help visualize the touch activity. I usually press the first trigger circle when the test page comes up so that finger location is shown with red dots.

Absolute X and Y represent the actual position on the screen.

Note: To convert from touchpad x values to pixel values, the formula is: x_pixel_value = (480 - (x_touchpad_value* 480/7552)) or roughly (480 - (x_touchpad_value/ 15.7))

Note: To convert from touchpad y values to pixel values, the formula is: y_pixel_value = (272 - (y_touchpad_value* 272/4248)) or roughly (272 - (y_touchpad_value/ 15.6))

Note:Event Code 40 (Misc) is finger count - a 0 finger count response occurs when all fingers are lifted

evtest /dev/input/touchscreen0
Supported events:
  Event type 0 (Sync)
  Event type 2 (Relative)
    Event code 0 (X)
    Event code 1 (Y)
    Event code 3 (?)
    Event code 4 (?)
  Event type 3 (Absolute)
    Event code 0 (X)
      Value   7104
      Min        0
      Max     7552
    Event code 1 (Y)
      Value   3793
      Min        0
      Max     4248
    Event code 24 (Pressure)
      Value     38
      Min        0
      Max      255
    Event code 28 (Tool Width)
      Value      1
      Min        0
      Max       15
    Event code 40 (Misc)
      Value      0
      Min        0
      Max        3
Testing ... (interrupt to exit)
Event: time 1235049035.290582, type 3 (Absolute), code 40 (Misc), value 1
Event: time 1235049035.290599, type 3 (Absolute), code 0 (X), value 5261
Event: time 1235049035.290605, type 3 (Absolute), code 1 (Y), value 2198
Event: time 1235049035.290611, type 3 (Absolute), code 24 (Pressure), value 45
Event: time 1235049035.290622, -------------- Report Sync ------------
Event: time 1235049035.301574, type 3 (Absolute), code 40 (Misc), value 0
Event: time 1235049035.301587, -------------- Report Sync ------------
Event: time 1235049035.464286, -------------- Report Sync ------------

Touchpad Behavior/Issues

Issue: finger movement was constant angle SE slow drag off the screen, but y value starts going the opposite way (red dots)

Also, Sometimes instead of bouncing back, the y value stays constant at the bottom for a few moments.

Issue: sliding up and down along rightmost part of screen (the point where response stops) doesn't reaches the edge, misses by 6 pixels at least

Note: To convert from touchpad x values to pixel values, the formula is: x_pixel_value = (480 - (x_touchpad_value* 480/7552)) or roughly (480 - (x_touchpad_value/ 15.7))

Event: time 1235044217.540923, type 3 (Absolute), code 0 (X), value 128
Event: time 1235044217.551825, type 3 (Absolute), code 0 (X), value 122
Event: time 1235044217.563645, type 3 (Absolute), code 0 (X), value 132
Event: time 1235044217.575124, type 3 (Absolute), code 0 (X), value 130
Event: time 1235044217.587195, type 3 (Absolute), code 0 (X), value 129
Event: time 1235044217.599259, type 3 (Absolute), code 0 (X), value 128
Event: time 1235044217.621653, type 3 (Absolute), code 0 (X), value 118
Event: time 1235044217.633288, type 3 (Absolute), code 0 (X), value 106
Event: time 1235044217.644908, type 3 (Absolute), code 0 (X), value 96
Event: time 1235044217.656954, type 3 (Absolute), code 0 (X), value 103
Event: time 1235044217.669067, type 3 (Absolute), code 0 (X), value 112
Event: time 1235044217.680619, type 3 (Absolute), code 0 (X), value 107
Event: time 1235044217.691534, type 3 (Absolute), code 0 (X), value 97
Event: time 1235044217.703118, type 3 (Absolute), code 0 (X), value 100
Event: time 1235044217.714842, type 3 (Absolute), code 0 (X), value 101
Event: time 1235044217.727203, type 3 (Absolute), code 0 (X), value 111
Event: time 1235044217.739245, type 3 (Absolute), code 0 (X), value 99
Event: time 1235044217.750476, type 3 (Absolute), code 0 (X), value 110
Event: time 1235044217.761358, type 3 (Absolute), code 0 (X), value 115
Event: time 1235044217.773007, type 3 (Absolute), code 0 (X), value 118

Good: South edge can be reached well

Event: time 1235045922.245107, type 3 (Absolute), code 1 (Y), value 1
Event: time 1235045922.256203, type 3 (Absolute), code 1 (Y), value 0
Event: time 1235045922.267118, type 3 (Absolute), code 1 (Y), value 5
Event: time 1235045922.278827, type 3 (Absolute), code 1 (Y), value 20
Event: time 1235045922.290419, type 3 (Absolute), code 1 (Y), value 10
Event: time 1235045922.302551, type 3 (Absolute), code 1 (Y), value 5
Event: time 1235045922.315103, type 3 (Absolute), code 1 (Y), value 7
Event: time 1235045922.326012, type 3 (Absolute), code 1 (Y), value 3
Event: time 1235045922.337073, type 3 (Absolute), code 1 (Y), value 1
Event: time 1235045922.348709, type 3 (Absolute), code 1 (Y), value 0
Event: time 1235045922.546877, type 3 (Absolute), code 1 (Y), value 14
Event: time 1235045922.558491, type 3 (Absolute), code 1 (Y), value 7
Event: time 1235045922.572850, type 3 (Absolute), code 1 (Y), value 3
Event: time 1235045922.581823, type 3 (Absolute), code 1 (Y), value 1
Event: time 1235045922.593718, type 3 (Absolute), code 1 (Y), value 0
Event: time 1235045923.164948, type 3 (Absolute), code 1 (Y), value 10
Event: time 1235045923.176277, type 3 (Absolute), code 1 (Y), value 5
Event: time 1235045923.187313, type 3 (Absolute), code 1 (Y), value 2
Event: time 1235045923.198983, type 3 (Absolute), code 1 (Y), value 1
Event: time 1235045923.210563, type 3 (Absolute), code 1 (Y), value 0

Good: north edge can be reached well

Event: time 1235046565.557028, type 3 (Absolute), code 1 (Y), value 4248
Event: time 1235046565.579488, type 3 (Absolute), code 1 (Y), value 4239
Event: time 1235046565.591116, type 3 (Absolute), code 1 (Y), value 4248
Event: time 1235046565.615649, type 3 (Absolute), code 1 (Y), value 4226
Event: time 1235046565.626566, type 3 (Absolute), code 1 (Y), value 4242
Event: time 1235046565.637704, type 3 (Absolute), code 1 (Y), value 4248

Issue: sliding up and down along leftmost part of screen (the point where response stops) doesn't reaches the edge, misses by 4 pixels at least

Note: To convert from touchpad y values to pixel values, the formula is: y_pixel_value = (272 - (y_touchpad_value* 272/4248)) or roughly (272 - (y_touchpad_value/ 15.6)) File:Squeezeplay0007-up-and-down-left.png

Event: time 1235046071.437279, type 3 (Absolute), code 0 (X), value 7464
Event: time 1235046071.449000, type 3 (Absolute), code 0 (X), value 7450
Event: time 1235046071.461130, type 3 (Absolute), code 0 (X), value 7451
Event: time 1235046071.472956, type 3 (Absolute), code 0 (X), value 7455
Event: time 1235046071.484653, type 3 (Absolute), code 0 (X), value 7457
Event: time 1235046071.495594, type 3 (Absolute), code 0 (X), value 7450
Event: time 1235046071.507221, type 3 (Absolute), code 0 (X), value 7458
Event: time 1235046071.518871, type 3 (Absolute), code 0 (X), value 7454
Event: time 1235046071.531018, type 3 (Absolute), code 0 (X), value 7452
Event: time 1235046071.543208, type 3 (Absolute), code 0 (X), value 7451
Event: time 1235046071.554474, type 3 (Absolute), code 0 (X), value 7472
Event: time 1235046071.565459, type 3 (Absolute), code 0 (X), value 7467
Event: time 1235046071.588745, type 3 (Absolute), code 0 (X), value 7464
Event: time 1235046071.600782, type 3 (Absolute), code 0 (X), value 7463
Event: time 1235046071.613075, type 3 (Absolute), code 0 (X), value 7462
Event: time 1235046071.635367, type 3 (Absolute), code 0 (X), value 7454
Event: time 1235046071.647039, type 3 (Absolute), code 0 (X), value 7469
Event: time 1235046071.658702, type 3 (Absolute), code 0 (X), value 7465
Event: time 1235046071.670866, type 3 (Absolute), code 0 (X), value 7463