mirror of
https://github.com/sinseman44/PyCNC.git
synced 2026-09-01 00:40:12 +00:00
153 lines
7.3 KiB
Markdown
153 lines
7.3 KiB
Markdown
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PyCNC is a free open-source high-performance G-code interpreter and
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CNC/3D-printer controller. It can run on a variety of Linux-powered ARM-based
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boards, such as Raspberry Pi, Odroid, Beaglebone and others. This gives you a
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flexibility to pick a board you are most familiar with, and use everything
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Linux has to offer, while keeping all your G-code runtime on the same board
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without a need to have a separate microcontroller for real-time operation.
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Our choice of Python as main programming language significantly reduces code
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base compared to C/C++ projects, reduces boilerplate and microcontroller-specific
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code, and makes the project accessible to a broader audience to tinker with.
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# Realtime Motor Control in Linux?
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Typically there is no way to control stepper motors from Linux runtime
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environment due to the lack of real time GPIO control. Even kernel based
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modules can not guarantee precise control of pulses for steppers.
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However, we can use a separate hardware module, DMA (Direct Memory Access)
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which provides high precision for GPIO outputs. This module can copy bytes which
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represent GPIO states from RAM buffer directly to GPIO with some clock based
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on main chip internal oscillator without using CPU's cores. Using such approach
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this project generates impulses for moving stepper motors and that is very
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precise way regardless CPU load and OS time jitter.
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This approach also allows to use Python language for this project. Typically,
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Python is not good choice for real time application, but since project just
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needs to set up DMA buffers and hardware will do the rest, Python become the
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perfect choice for easy development of this project.
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Video demo - [YouTube video](https://youtu.be/41wdmmztTNA)
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And the original video when PyCNC was just a prototype [YouTube video](https://youtu.be/vcedo59raS4)
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# Current gcode and features support
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* Commands G0, G1, G2, G3, G4, G17, G18, G19, G20, G21, G28, G53, G90, G91, G92,
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M2, M3, M5, M30, M84, M104, M105, M106, M107, M109, M114, M140, M190, M300 (connected to servo motor) are
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supported. Commands can be easily added, see [gmachine.py](./cnc/gmachine.py)
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file.
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* Two axis are supported - X, Y. (Z and E are not supported)
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* Circular interpolation for XY planes is supported.
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* Spindle with rpm control is not supported.
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* Extruder and bed heaters are not supported.
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* Hardware watchdog.
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# Watchdog
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PyCNC uses one of DMA channels as hardware watchdog for safety purpose. If
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board, OS or PyCNC hangs this watchdog should disable all GPIO pins(by
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switching them into input state, for RPi this would be GPIO0-29) in 15 seconds.
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Since there is a high current and dangerous devices like heated bed, extruder
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heater, this feature should prevent uncontrollable overheating. But don't count
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on such software features too much, they can hang too or output MOSFET become
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shorted, use hardware protection like thermal cutoff switches in your machines.
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# Hardware
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Currently, this project supports Raspberry Pi 1-3. Developed and tested with
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RPI1.2b. And there is a way to add new boards. See [hal.py](./cnc/hal.py) file.
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_Note: Current Raspberry Pi implementation uses the same resources as on board
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3.5 mm jack(PWM module), so do not use it. HDMI audio works._
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# Config
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All configs are stored in [config.py](./cnc/config.py) and contain hardware
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properties, limitations and pin names for hardware control.
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Initially, Raspberry Pi implementation should be connected to A4988, DRV8825 or any other
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stepper motor drivers with DIR and STEP pin inputs.
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For this branch (l293d), Raspberry Pi implementation should be connected to L293D stepper motor drivers.
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Default config is created for Raspberry Pi 1.2b and PiPlot2D system and this wiring config:
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| Circuit name | RPi pin name | Note |
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|------------------|--------------|-----------------|
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| X cmd A | GPIO12 | to first L293d |
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| X cmd A' | GPIO16 | to first L293d |
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| X cmd B | GPIO20 | to first L293d |
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| X cmd B' | GPIO21 | to first L293d |
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| X endstop | GPIO10 | |
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| Y cmd A | GPIO24 | to 2nd L293d |
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| Y cmd A' | GPIO25 | to 2nd L293d |
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| Y cmd B | GPIO8 | to 2nd L293d |
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| Y cmd B' | GPIO7 | to 2nd L293d |
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| Y endstop | GPIO9 | |
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| servo motor cmd | GPIO18 | to sg90 servo |
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| display data 4 | GPIO6 | to HD44780 |
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| display data 5 | GPIO13 | to HD44780 |
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| display data 6 | GPIO19 | to HD44780 |
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| display data 7 | GPIO26 | to HD44780 |
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| display clk edge | GPIO5 | to HD44780 |
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| display Reg Sel | GPIO11 | to HD44780 |
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| button up | GPIO17 | |
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| button ok | GPIO22 | |
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| button down | GPIO27 | |
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This is the PiPlot2D system based on a Raspberry Pi 1.2b, L293d Stepper motor drivers and
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DC 5V 2 phases 4 wires stepper motor recovered from old DVD-roms.
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Draw dimensions : 4cm x 5cm
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# Usage
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Just clone this repo and run `./pycnc` from repo root. It will start in
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interactive terminal mode where gcode commands can be entered manually.
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To run file with gcode commands, just run `./pycnc filename`.
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Optionally, `pycnc` can be installed. Run
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```bash
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sudo pip install .
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```
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in repo root directory to install it. After than, `pycnc` command will be added
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to system path. To remove installation, just run:
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```bash
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sudo pip remove pycnc
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```
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# Performance notice
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Pure Python interpreter would not provide great performance for high speed
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machines. Overspeeding setting causes motors mispulses and probably lose of
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trajectory. According to my tests, Raspberry Pi 2 can handle axises with 400
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pulses on mm with top velocity ~800 mm per min. There is always way out! :)
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Use JIT Python implementation like PyPy. RPi2 can handle up to 18000 mm per
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minute on the machine with 80 steps per millimeter motors with PyPy.
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_Note: Raspbian has outdated PyPy version in repositories(v4.0). Moreover v4.0
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has issue with `mmap` module implementation. Use PyPy v5.0+, download it for
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your OS from [here](https://pypy.org/download.html)._
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PyPy installation:
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```bash
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wget wget https://bitbucket.org/pypy/pypy/downloads/pypy2-v5.7.1-linux-armhf-raspbian.tar.bz2
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sudo mkdir /opt/pypy
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sudo tar xvf pypy2-v5.7.1-linux-armhf-raspbian.tar.bz2 --directory /opt/pypy/ --strip-components=1
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sudo ln -s /opt/pypy/bin/pypy /usr/local/bin/pypy
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```
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# Project architecture
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# Dependencies
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Nothing for runtime. Just pure Python code.
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For uploading to PyPi there is a need in `pandoc`:
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```bash
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sudo dnf install pandoc
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sudo pip install pypandoc
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```
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# GCode simulation
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Just a link, mostly for myself :), to a nice web software for gcode files
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emulation (very helpful for manual creating of gcode files):
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[https://nraynaud.github.io/webgcode/](https://nraynaud.github.io/webgcode/)
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# License
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see [LICENSE](./LICENSE) file.
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# Author
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Nikolay Khabarov
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