There is a nice little led matrix moard from PIMORONI, “SCROLL PHAT HD”. The form factor is for the pi zero, but it runs well also with a pi 3.

scratchClient offers support for this board.

The interface allows to set pixel with brightness, write large and somewhat smaller text and of course clear the display.

There is a sample scratch script in scratch/scrollphathd/scroll_phat_hd.sb

There are quite a few commands from scratch which need parameters.
This is not a trivial task with scratch. Here a variable is used as a ‘command’-Variable ‘sph_command which receives operation names optionally with parameters.

Clear the display. There is also a broadcast command for this ‘clearDisplay’

Set a pixel at x=1, y=1, brightness = 1.0. Valid ranges are x in [0..16], y in [0..6], brightness is [0.0..1.0]. Values out of scope are ignored.

Draw a box between two pixels, here between [0;0] and [17;7] with brightness 0.3. This command effectively sets all led to on.

There are two text variables provided with a 5*7-font and a 3*5 font. Not all chars are supported. The 5*7 font basically supports ascii, the 3*5 font supports digits and some extra chars as ,;.:-_+\/.
The fonts are defined in ‘pseudographics’ in a python file and can easily be expanded.

There is a sample config file available, start scratchClient with

cd ~/scratchClient
python src/scratchClient.py -c config_scrollphathd

The adapter code has been written based on code from pimoroni.