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PolarGraph Network Hack: PolarshieldSD v3.0e modified to use WiFi for communication between controller and server. ESP32, stepper motors, and the Travelling Salesman Problem

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PolarGraph Network Hack

A modified version of:
Polargraph: An open source art project http://www.polargraph.co.uk/

Cat

A PolarshieldSD V3 ESP32, with polargraphserver and polargraphcontroller, modified to use WiFi network for communication between Controller and Server.

The Polargraph Software

COMMS

The Doxygen documentation for the polargraphserver can be found here: https://obstruse.github.io/PGNH

Installation

To compile and upload, use VSCode/PlatformIO. For the first upload, use the [env:TTY0] Project Environment (edit platformio.ini to match your serial port).

The first time it boots it will create a Soft Access Point with SSID: polargraph and PSK: carbondioxide.
Open http://polargraph.local/config to configure the WiFi

For uploads after the first, use the [env:OTA] Project Environment (edit platformio.ini for machine host/IP)

PolargraphController requires Processing-2.2.1. Use File -> Export Application from the IDE to create the application, or from the command line: $ processing-java --export --output=build --sketch=polargraphcontroller

Changes

  • Network
    • WiFi connection between server and controller on port 12345
    • Web server for configuration and status
    • Firmware update via OTA
  • Multi-task
    • WiFi Task
    • HTTP Task
    • Comms Read Task
    • Comms Execute Task
    • LCD Task
    • SD Plot Task (created when needed)
    • Loop Task (empty and paused)
    • All tasks run in parallel at same priority with no conflicts.
  • Speed Improvements
    • Instead of reading one character every 20msec, it reads all when available
    • Begins buffering the next command while the current command is executing
    • Comms plot speed equal to SD plot speed

Travelling Salesman Problem

noun: travelling salesman problem

a mathematical problem in which one tries to find the shortest route that passes 
through each of a set of points once and only once.

The problem can be solved by analyzing every round-trip route to determine the shortest one. 
However, as the number of destinations increases, the corresponding number of roundtrips 
surpasses the capabilities of even the fastest computers. 

TSPwiki

With 10 destinations, there can be more than 300,000 roundtrip permutations and combinations. 
With 15 destinations, the number of possible routes could exceed 87 billion.

A TSP "solution" for a 15,000 point map:

MOM-4

Create the Vector File

Make a Grayscale Image

Open your image in GIMP
Turn the color information monochrome “Image -> Mode -> Grayscale“
Open the color levels “Colors -> Levels“
Wash out the image by adjusting “All Channels” in the pop-up window to some value to 200 
((Values between 180 and 245 should work well))

Make a Stippled Image

Turn the washed out grayscale image into a stippled image “Create Image->Mode->Indexed“
Select these options in the pop-up window
    Use black and white (1-bit) palette): Checked
    Remove unused colors from colormap: Checked
    Color dithering: Floyd-Steinberg (normal)
Click “Convert“
Save the file in the “Portable Bit Map” format “File->Save As” and saving the file with the extension “.pbm“
    If given the option, choose to save the PBM file in the “Raw” format

Convert PBM to Vector

Use tspart.py from tsp_art_tools

Run polargraphcontroller

Setup machine parameters and enter Network Host:

Network Host

Home the machine; home the controller; start the queue
Load/Resize/Move Vector; Draw Vectors

Vector Commands

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PolarGraph Network Hack: PolarshieldSD v3.0e modified to use WiFi for communication between controller and server. ESP32, stepper motors, and the Travelling Salesman Problem

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