The existing code was broken in a few ways:
- It didn't use the correct operator precedence for the VSCRDEF VSA
variable: it needed some extra parentheses to be correct.
- It used the configured height instead of the actual display height
for calculating VSA, which is incorrect. TFA+VSA+BFA must always be
exactly 320, even if a lower value is configured.
- If a lower than 320 pixel height is configured, the bottomFixedArea
parameter applied to the whole 320 pixel screen height. Because this
seems counter intuitive (and relies on properties of any given
screen), I've changed it to work from the actual visible bottom of
the screen (which may be smaller than 320 pixels).
TODO: this doesn't take RowOffset into account, while it probably
should.
I haven't fixed the st7735 implementation, because I didn't have example
code on hand that would easily work on a st7735 screen. This is left as
a TODO for the future.
Many displays don't have the TE pin exposed. But those that do have the
pin (for example, the PyPortal) can use it to synchronize writing a new
image to the display. When implemented correctly, tearing can be avoided
entirely.
This commit also changes the LCD refresh direction to either
top-to-bottom or left-to-right depending on the rotation. Previously it
might refresh from right-to-left or bottom-to-top. This has little
impact on code that doesn't use the TE line, but code that does now only
needs to worry about two cases (top-to-bottom and left-to-right) instead
of four.
(Unfortunately, it appears that the hardware doesn't support changing
the major LCD refresh order so code that wants to do tear-free rendering
still needs to care about these two cases).
* Unify the Rotation type, so that SetRotation can be used in
interfaces.
* Add Rotation() method to these displays, so that the current
rotation can be read.
* Change SetRotation() so that it can return an error (if the given
rotation isn't supported).
The API looks like this and is based on the PCA9685 PWM chip:
Sleep(sleepEnabled bool) error
It will set the LCD panel to a low power state (not displaying any
image) but memory contents will be preserved.
It can not be skipped as you may call setwindow even if device is not ready for data write to buffer.
Data can only be written if last command was Memory Write or Write Memory Continue which was not guaranteed
There's no performance loss as having the exact same window on a consecutive call is extremely unlikely
- Fixed some typos and added a few missing comments to please go-lint
Ayke van Laethem
deadprogram
sago35
Amblyopius
BCG
ardnew
Daniel Esteban