NOTE: This is not a step by step guide for building a drawbot. We are working on this and will publish it when ready on blackstripes.nl

Blackstripes drawbot driver

This is the driver we use at blackstripes.nl. It controls two stepper motors and a single solenoid for pen lifting. The main features are:

1. Direct SVG workflow. Upload svg to the Raspberry-PI through web based interface, no translation to g-code needed.
2. Speed management through web interface.
3. Automatic lookahead acceleration management.
4. Simple Lua scripting interface. moveTo(x,y) penUp() penDown()
5. Can control V-plotters as well as other machines.
6. Standalone operation with a single Raspberry-PI

Example video.

Dependencies

This will run on a Raspberry-PI model B+. Xenomai must be Installed.

This project uses the following excellent opensource software:

###LodePNG: https://github.com/lvandeve/lodepng

###Nano SVG: https://github.com/memononen/nanosvg

###lua-5.2.3: https://github.com/lua/lua

###inih: https://github.com/benhoyt/inih

How to compile

###On the Raspberry-PI (Xenomai enabled model B+)

1. clone this repo
2. build the server
   1. cd to sketchy_server
   2. make
   3. make install
3. build the driver
   1. cd to sketchy_driver
   2. make pi
   3. make install
4. build the (optional) preview-driver
   1. cd to sketchy_driver
   2. make preview
   3. make installp

Now cd into the build directory and start the server.

sudo nohup ./sketchy-server

Now find out the IP-address of your Raspberry-PI and point your webbrowser to port 8000. (http://192.168.x.xxx:8000) You should see this page:

GPIO pins Raspberry-PI (model B+)

These are the pins to be connected to the stepper drivers and the relay to control the solenoid.

#define RIGHT_CLOCK RPI_V2_GPIO_P1_11
#define RIGHT_DIR RPI_V2_GPIO_P1_12
#define LEFT_CLOCK RPI_V2_GPIO_P1_13
#define LEFT_DIR RPI_V2_GPIO_P1_15
#define SOLENOID RPI_V2_GPIO_P1_16

Cross compilation

For crosscompiling we have created a crosscompile target in the make files. Our cross-compiling machine has these cross compiling tools installed:

####Toolchain git clone https://github.com/raspberrypi/tools

You can then copy the toolchain to a common location such as /tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian, and add /tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian/bin to your $PATH in the .bashrc in your home directory. For 64bit, use /tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin. While this step is not strictly necessary, it does make it easier for later command lines!

To find out the lib path of this cross-compiler you need to do this

$ arm-linux-gnueabihf-gcc -print-sysroot

this will show where to look for libc.

also:

$ arm-linux-gnueabihf-gcc -print-search-dirs

You need to have rpi compiled libs of xenomai and native. I got them from a xenomaied Raspberry pi from /usr/lib/

Then you need to copy these libnative.* and libxenomai.* files into this sysroot in the folder [sysroot compiler]/usr/lib/

That together with some modified targets for using the right compiler include path and you are ready to roll.