Currently we draw and send the screens for a graphical LCD all at once.
We draw in two or four parts but draw them directly behind each other.
For the tested status screen this takes 59-62ms in a single block.
During this time nothing else (except the interrupts) can be done.
When printing a sequence of very short moves the buffer drains - sometimes until it's empty.
This PR splits the screen update into parts.
Currently we have 10 time slots. During the first one the complete screen is drawn. (60,0,0,0,0,0,0,0,0,0,0)
Here i introduce pauses for doing other things. (30,30,0,0,0,0,0,0) or (15,15,15,15,0,0,0,0,0,0)
Drawing in consecutive time slots prevents from lagging too much. Even with a 4 stripe display all the drawing is done after 400ms.
Previous experiments with a even better distribution of the time slots like
(30,0,0,0,0,30,0,0,0,0) and (15,0,15,0,15,0,15,0,0,0) did not feel good when using the menu, because of too much lag.
Because of the previous PRs to speed up the display updates and especially reducing the difference between drawing 2 or 4 stripes,
it now makes sense for the REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER to go from 2 to 4 stripes. This costs about 1-2ms per complete
screen update, but is payed back by having partial updates lasting only the half time and two additional brakes. Also ~256 byte of
framebuffer are saved in RAM.
13:45:59.213 : echo: #:17 >:13 s:30; #:16 >:13 s:29; S#:33 S>:26 S:59
13:46:00.213 : echo: #:16 >:14 s:30; #:17 >:13 s:30; S#:33 S>:27 S:60
13:46:01.215 : echo: #:17 >:13 s:30; #:16 >:13 s:29; S#:33 S>:26 S:59
13:46:02.215 : echo: #:16 >:13 s:29; #:16 >:14 s:30; S#:32 S>:27 S:59
13:46:03.214 : echo: #:17 >:13 s:30; #:17 >:13 s:30; S#:34 S>:26 S:60
13:46:04.214 : echo: #:16 >:13 s:29; #:16 >:14 s:30; S#:32 S>:27 S:59
13:46:05.212 : echo: #:16 >:14 s:30; #:17 >:13 s:30; S#:33 S>:27 S:60
13:46:06.212 : echo: #:17 >:13 s:30; #:16 >:13 s:29; S#:33 S>:26 S:59
03:30:36.779 : echo: #:8 >:7 s:15; #:10 >:7 s:17; #:8 >:6 s:14; #:8 >:7 s:15; S#:34 S>:27 S:61
03:30:37.778 : echo: #:8 >:6 s:14; #:10 >:7 s:17; #:9 >:7 s:16; #:8 >:6 s:14; S#:35 S>:26 S:61
03:30:38.778 : echo: #:8 >:6 s:14; #:11 >:7 s:18; #:8 >:6 s:14; #:8 >:7 s:15; S#:35 S>:26 S:61
03:30:39.777 : echo: #:8 >:6 s:14; #:10 >:7 s:17; #:8 >:8 s:16; #:8 >:6 s:14; S#:34 S>:27 S:61
03:30:40.780 : echo: #:8 >:6 s:14; #:11 >:7 s:18; #:8 >:6 s:14; #:8 >:6 s:14; S#:35 S>:25 S:60
03:30:41.780 : echo: #:9 >:6 s:15; #:10 >:7 s:17; #:8 >:6 s:14; #:9 >:6 s:15; S#:36 S>:25 S:61
03:30:42.779 : echo: #:8 >:6 s:14; #:10 >:8 s:18; #:8 >:6 s:14; #:8 >:6 s:14; S#:34 S>:26 S:60
03:30:43.778 : echo: #:9 >:6 s:15; #:10 >:7 s:17; #:8 >:7 s:15; #:9 >:6 s:15; S#:36 S>:26 S:62
#: draw a stripe
>: transfer a stripe
s: sum of of draw and transfer for one stripe
S#: sum of draws for a complete screen
S>: sum of transfers for a complete screen
S: time to draw and transfer a complete screen
lcd_update can take so much time that the block buffer gets drained if
there are only short segments. This leads to jerky printer movements for
example in circles and a bad print quality.
This change implements a simple check: Only if the block currently
executed is long enough, run lcd_update.
This also means the printer will not show actual values on the LCD nor
will it respond to buttons pressed. A option that keeps the menu
accessible is also available.
Aditionaly, slow down if a block would be so fast that adding a new
block to the buffer would take more time. In this case, the buffer would
drain until it's empty in worst case.
