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Update README with the new backlight implementation details

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Pim van Pelt
2017-11-28 15:42:52 +01:00
parent 7041526a39
commit 1ef7195728
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README.md
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@ -169,18 +169,17 @@ added time `widget`.
The Featherwing has a PWM based backlight. The implementaion in
`src/backlight.c` shows a way to dim the screen when it is not in use.
The way this works, is by means of `backlight_keepalive()` which sets the
backlight on, and installs a timer (by default for 10 seconds). Each time
the user touches the screen, the timer is re-initialized. If the user does
not touch the screen, the timer invokes the callback `backlight_keepalive_cb()`
which will set turn the screen off: it will install a target duty cycle and
time to get to that target (usually 1000ms). Then it'll start a repeating
a 10ms timer that dims the backlight until the target it reached, after
which it deinstalls itself. See `backlight_fader_cb()` for details. Very slick!
backlight on, and updates `backlight_last_keepalive`. A timer checks if
the last keepalive call hasn't been too long ago, and if it was, it initiates
a screen dimmer by setting a new target duty cycle and time to get to that
target (usually 1000ms). Then it'll start a repeating a 20ms timer that dims
the backlight until the target it reached, after which it deinstalls itself.
See `backlight_fader_cb()` for details. Very slick!
If the screen is off, `backlight_active()` will return false. The main
`touch_handler()` (the one that gets interrupts from the STMPE610), will
ignore the first `TOUCH_DOWN` and `TOUCH_UP` events in that case, but it
will wake up the screen again by setting the backlight back on.
will wake up the screen again by calling `backlight_keepalive().`
### Other tricks