This is a first go at it, done by naive replacing of all array
operations with corresponding operations on the list. Note that
there is a lot of unnecessary type conversions, here. Also, list_pop
has been copied, because it's decalerd STATIC in py/objlist.h
Since we want to expose the list of group's children to the user,
we should only have the original objects in it, without any other
additional data, and compute the native object as needed.
* Comment on the reason for scaling by 256
* Divide by 256 instead of shifting
* fix a cast; eliminate an unneeded roundf() to get a few bytes code back
On the Pico, this increases the "fill rate" of
pixels[:] = newvalues
considerably. On a strip of 240 RGB LEDs, auto_write=False, the timings
are:
|| Brightness || Before || After || Improvement ||
|| 1.0 || 117 kpix/s || 307 kpix/s || 2.62x ||
|| 0.07 || 117 kpix/s || 273 kpix/s || 2.33x ||
It's worth noting that even the "before" rate is fast compared to the
time to transmit a single neopixel, but any time we can gain back
in the whole pipeline will let marginal animations work a little better.
To set all the pixels in this way and then show() gives a pleasant bump
to the framerate, from about 108Hz to 124Hz (1.15x)
The main source of speed-up is using integer math instead of floating
point math for the calculation of the post-scaled pixel values. A slight
secondary gain is achieved by avoiding the scaling altogether when
the scale factor is 1.0.
Because the math is not exactly the same, some scaled pixel values may
change by +- 1 RGBW "step". In practice, this is unlikely to matter.
The gains are bigger on the Pico and other M0 microcontrollers than M4
microcontrollers with floating point math in the hardware.
Happily, flash size is also improved a bit on the Pico build I did,
going from
> 542552 bytes used, 506024 bytes free in flash firmware space out of 1048576 bytes (1024.0kB).
to
> 542376 bytes used, 506200 bytes free in flash firmware space out of 1048576 bytes (1024.0kB).
* Introduce explicit serpentine: bool argument instead of using negative
numbers (thanks, ghost of @tannewt sitting on one shoulder)
* Fix several calculations of height
Testing performed (matrixportal):
* set up a serpentine 64x64 virtual display with 2 64x32 tiles
* tried all 4 rotations
* looked at output of REPL
Changed calls: PointSize(), LineWidth(), VertexTranslateX() and VertexTranslateY()
Units for all the above are now pixels, not fixed-point integers. This matches OpenGL.
Docstrings updated accordingly
The RP2040 is new microcontroller from Raspberry Pi that features
two Cortex M0s and eight PIO state machines that are good for
crunching lots of data. It has 264k RAM and a built in UF2
bootloader too.
Datasheet: https://pico.raspberrypi.org/files/rp2040_datasheet.pdf
