This repo contains an experiment to drive epaper display, connected to an esp32s2 chip. we use the micropython firmware on the chip, with additional microython libraries for mqtt, and epaper spi control

• Evaluating the ease of multi device control implementation, and microython maturity

• Evaluating the deployment options to lean the install of devices

• Evaluating semantic and protocol over mqtt to control displays

• Evaluating the ease of creating new screens and design toolchain

• download the micropython firmware, and esptool.py it !

install the command line to a venv python3 -mvenv p3 source p3/bin/activate pip3 install -r requierments_dev.txt

put the python files :

cd device_code
ampy --port /dev/ttyACM0 put *

ePaper display 400x300 in BW colors, in this design the esp32s2 implements a display server that offers the following primitives :

• clear() : clear the screen
• picture( p, x, y ) : display a picture at a specific location on the screen
• text (box, textstring) : display a text in a box
• update(): apply the in-buffer to the screen. (this primitive is quite slow, due to epaper technology)

These primitives are send thought mqtt, as commands, and evaluated within the python interpreter. see device_code/display.py

On the agent side (epaper_info.py), the screens are not directly implemented using code (too long).

An SVG template is taken and dynamic values are replaced within the svg document (using templating) and then rasterized using cairosvg.

The template is drawn in Inkskape, some text box are named for text replacement with weather api content.

The whole display is then splitted into small image tiles and sent over the mqtt topic as below :

p = p64("///8////wP///f///8D///z////A///8////wP///f///8D///z////A///8////wP///f///8D///z////A///8////wP///f///8D///z////A///8////wP///f///8D///z////A///8////wP///f///8D///z////A///8////wP///f///8D///z////A///8////wP///f///8D///z////A///8////wP///f///8D///z////A///8////wP///f///8D///z////A///8////wP///f///8BSlKT////AAAAA////wP///////8D////////A////////wP///////8D////////A////////wP///////8D////////A////////wP///////8D////////A////////wP///////8D////////A////////wP///////8A=", 50, 50)
d.picture(p, 350, 250)

After having sent all the tiles, a final d.update() is sent over the wire to materialize the reconstructed image on the screen.