Quote:
Originally Posted by ixtab
 I found a use case for the z-force input device in conjunction with gizmod: "Violently shake the device to reboot". |
z-force? That is what I meant when I suggested that these device-specific names might not be trustworthy. You might think that having "force" in the name makes it the accelerometer, but it turns out that this is the name of the touchscreen device.
The accelerometer is a different device (which CAN detect violent shaking, by the way, so your IDEA is sound).
We just need a reliable method of detecting a device REGARDLESS of its specific device file name, or its descriptive name either. Only its PROPERTIES are important.
EDIT: Without actually doing the research, I think we can guess why they called the touchscreen device "z-force"... When you apply force, your finger tip deforms, blocking more light, so you CAN indirectly determine the amount of force being applied to the touchscreen.
There is a nifty little toy built into the touch that will demonstrate this (and what I used to prove that you can determine the diameter of a coin placed on the touchscreen):
mount /dev/mmcblk0p2 /mnt/mmc
/mnt/mmc/usr/local/bin/zforcediag
This cool little tool shows how much light your finger is blocking from the X and Y light sensors. It also demonstrates that you can interpolate much higher resolution than expected by comparing the ratio of light blockage from the outer partially blocked sensors. You can see in the kindle touch teardown photos that there are not many LEDs or photosensors on the touch PCB, so analog interpolation is needed to get the 4096x4096 high resolution we get from this device. Also, it is interesting to see that we can read the touchscreen at a lower level (individual LEDs) than is provided by input device events.