Plotter-development

Python controller for a home-built 2D pen plotter, running on a Raspberry Pi and driven by G-code files.

Hardware

Raspberry Pi with an Adafruit Motor HAT (used through adafruit_motorkit), two stepper motors on stepper1 and stepper2.
Hobby servo on GPIO 14 that lifts and lowers the pen (driven through pigpio).
Two limit switches for homing: GPIO 16 (vertical) and GPIO 17 (horizontal).

plotter_controller.py holds the nc_head class. Both steppers turn together for every move: opposite directions move the head up or down, the same direction moves it left or right. Steps are converted to millimetres with a calibration factor (scale_x_y draws test squares so the real distances can be measured and entered).
Homing (end_travel) raises the pen, drives down until the vertical switch opens, then left until the horizontal switch opens, and sets the position to (0, 0).
G-code support: G0 fast moves, G1 linear moves, G2/G3 arcs (approximated by short segments, 0.05 rad steps), G91 relative moves. The pen goes down when Z is negative and up otherwise.
main.py is the text menu: go to origin, load a G-code file, plot, set (0, 0), manual control, release steppers, exit.
Manual control uses the arrow keys (move), Space (pen up), Enter (pen down) and E (exit), read over SSH with sshkeyboard.
file_sender.py is a small Flask app with an upload page. It accepts .gcode files, keeps the lines that start with G and saves them in shared_documents/ as name_N.txt, which is where main.py looks for files.

On the Raspberry Pi, with I2C enabled and the pigpio daemon running:

pip install -r requirements.txt
sudo pigpiod
python main.py

To send a G-code file to the Pi, start the upload server and open it in a browser:

python file_sender.py

The upload form in templates/index.html posts to http://127.0.0.1:5000/upload/, so open the page on the Pi itself or change that address.

main.py: menu and G-code interpreter.
plotter_controller.py: motor, servo and limit switch control.
file_sender.py, templates/, static/: upload server and its page.
key_control.py: test of keyboard reading.
draft.py: test of the limit switches with two LEDs on GPIO 20 and 21.
shared_documents/: G-code files ready to plot (cat_1.txt, engranajes_1.txt, engranajes_2.txt, gato_cuadrado_1.txt).
static/engranajes.gcode, engranajes.svg: source drawing of the gears example.

Pablo Tuñón Laguna, 2024. MIT licence.