kscan_ft5336 doesn't provide proper up/down information when polling, and hogs resources in interrupt mode

[dhoove]

The 'pressed' value that is provided by the callback is only 1 if the touchpad was being pressed at the moment it was being sampled. If you press quickly between sampling periods, 'pressed' will always remain zero. One way to solve this problem is by activating interrupt mode. But in this case, the interrupts are generated at high frequency (approximatly 40Hz), causing significant I2C traffic and hogging resources.

To reproduce:

• set KSCAN_FT5336_PERIOD to 1000
• set KSCAN_LOG_LEVEL_INF to Debug so that you can observe the touch events in the log
• create a devicetree alias to touch_controller named kscan0
• make sure the touch_controller has a int-gpios line defining the IRQ line.
• make sure that touch_controller's i2c interface is up and running
• create the device with device_get_binding(DT_LABEL(DT_ALIAS(kscan0)))
• attach a callback with kscan_config(), and enable the callback with kscan_enable_callback().
• observe the 'pressed' column of the log, while quickly touching and releasing the display. Most of the time, the pressed value will never change to 1.

This problem is disturbing because accurate press detection results in high CPU use, both in polling and interrupt mode.

[MaureenHelm]

Which board and zephyr version are you using?

[dhoove]

Hi,I just added a board file to the PR for the STM32L476 nucleo board.Cheers,DavidOn 6 Apr 2021 19:41, Maureen Helm @.***> wrote: Which board are you using?

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[gmarull]

related PR: https://github.com/zephyrproject-rtos/zephyr/pull/33996

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