In the previous posts in this series, I hacked up a Canon camera to take pictures with an electronic trigger, built a cable to connect the camera to my MakerBot, and hacked the MakerBot’s firmware to enable it to trigger the camera in response to commands from the controlling computer.

The final step was to hack the desktop software that controls the MakerBot - ReplicatorG.

What is ReplicatorG?

From the ReplicatorG website:

[ReplicatorG] is the software that will drive your CupCake CNC, RepRap machine, or generic CNC machine. You can give it a GCode or STL file to process, and it takes it from there. Its cross platform, easily installed, and is based on the familiar Arduino / Processing environments.

For my purposes, ReplicatorG provides two things. First, RepG is a user interface for controlling the MakerBot hardware:

Second, RepG reads G-code files describing how to build an object, and transmits them to the MakerBot over the USB:

Of course, ReplicatorG is open source, and the code is available on GitHub! So, it was simple to clone their repository and start hacking on it myself.

Camera Control via ReplicatorG

While it was relatively simple to update the extruder controller firmware to make it camera-aware, ReplicatorG is a bit more complicated. My first goal was to hack a new “Camera” checkbox into the control panel. Whenever the box was checked, the camera would take pictures. Whenever the box was unchecked, the camera would be idle.

You can find the code required for these changes in this commit on GitHub, but I will try to briefly break them down here:

• Define a new machine. In the machines.xml.dist file, I defined an experimental MakerBot configuration named "EXPERIMENTAL - Cupcake CNC w/HBP and remote camera". It is essentially a copy of the typical MakerBot configuration with a heated build platform, but in the <tool> definition, I also added a camera="true" attribute.
• Update the tool model. In ToolModel.java, I added code to represent whether the tool has an attached camera, whether the camera is activated, and how to parse the camera attribute out of machines.xml.
• Update the machine driver model. In Driver.java, DriverBaseImplementation.java, and Sanguino3GDriver.java, I added the definitions and implementations to triggerCamera() and stopTriggeringCamera(). This is the code that actually sends the TOGGLE_CAMERA serial command to the extruder controller, which I also defined in ToolCommandCode.java.
• Update the control panel interface. In ExtruderPanel.java, I added the code to draw a new label and checkbox named "Camera", if the machine is configured for a camera, and to respond to check/uncheck events by calling triggerCamera() or stopTriggeringCamera().

Compiling and Running the new ReplicatorG

Compiling ReplicatorG is pretty simple, so long as you have a reasonable JDK environment and have Ant on your path. There are basically two steps:

1. Copy machines.xml.dist to machines.xml`.
2. Run the proper dist-linux.sh, dist-mac.sh, or dist-windows.sh.

ReplicatorG will be compiled and packaged up into the dist/ directory in two forms: an installable package for the chosen platform, and an unpacked version that you can run directly.

Opening up my modified version of ReplicatorG, I selected the “EXPERIMENTAL - Cupcake CNC w/HBP and remote camera” profile from the Machine -> Driver menu, opened up the control panel, and was happy to see this:

After hooking up my camera to the extruder controller’s D9 port, and starting the Remote Button script on the camera, I was able to take pictures by quickly toggling the camera checkbox on and off. I could also leave the checkbox activated to make the camera take pictures continuously.

Automatic Triggering with G-codes

Being able to trigger the camera by hand is all well and good, but my goal was to take pictures automatically at the end of every layer. To do this, I needed to be able to embed camera trigger commands in the G-code for building each individual object.

Looking at the ReplicatorG G-code docs, and the (machine-specific) M-code docs, I chose two codes for working with the camera:

• M150 - Trigger Camera
• M151 - Stop Triggering Camera

I may have to change these in the future, as the main ReplicatorG development team claim G- and M-codes for other features, but these work for now.

Modifying ReplicatorG to accept these M-codes (GitHub commit here) was straightforward: update GCodeParser.java to recognize the codes, and call the appropriate triggerCamera() and stopTriggeringCamera() methods.

I could now construct a G-code file which, when “built” in ReplicatorG, would take a picture on demand:

M150     (trigger the camera)
G4 P700  (wait 0.7 seconds for the camera to activate)
M151     (stop triggering)
G4 P1300 (wait 1.3 seconds for the camera to finish)

Finally, it was time to edit up the G-code for the models I want to photograph.

Typically, G-code is generated by taking a 3D object in STL format and running it through the Skeinforge tool. Skeinforge is a set of Python scripts, which means it is not too difficult to insert your own code.

For now, however, I decided to make a simple hack using a Perl script I wrote called add_camera_events.pl. It works by looking for (</layer>) comments, which signal the end of a layer of printing, and inserts lines to:

1. Move to a standard pose (X=0, Y=-45),
2. Trigger the camera and wait for it to finish, and
3. Move back to the original position

You can find the source for this script in the add_camera_events.pl gist. The source for all of my changes to ReplicatorG are on GitHub, in the “schmarty-camera” branch of my fork of ReplicatorG.

And with that, the computer aspect of this system was finally done!

Wrap Up

Phew! So far I’ve hacked a camera, wired it to the MakerBot, updated the MakerBot firmware to trigger it, updated ReplicatorG to trigger it, and written a script to update G-code files with camera triggers at the end of each layer.

So… does it work? You bet! Stay tuned for more examples and a breakdown video of this whole project in the final post in this series!

• Part 1: Remote control camera with CHDK
• Part 2: Wiring it up!
• Part 3: Updating the MakerBot Firmware
• Part 4: Updating ReplicatorG [YOU ARE HERE]
• Part 5: Printing with the Camera!

Recently (thanks to the Internet), I figured out how to remote control a digital camera over USB using CHDK. However, if I wanted my MakerBot to be able to automatically control that camera, I needed a way to wire it up!

CHDK’s remote USB trigger functionality works by detecting when it receives power over USB.  This happens when two wires inside the USB mini-B cable are connected to power: the red wire gets 5 volts, and the black wire gets connected to ground.

So, I chose to find somewhere on the MakerBot’s electronics to hook up these power and ground wires such that the MakerBot could control when the red wire receives 5V.  The MakerBot uses RepRap Generation 3 electronics, and let me tell you, the gen 3 electronics documentation is fantastic!  Unfortunately, the docs for the main motherboard reveal that there are some free I2C headers for connecting serial devices, but no free general I/O pins.

Luckily, the extruder controller docs show two free digital pins, conveniently broken out with 5V and ground connections next to them.  These are digital pins D9 and D10.  According to the docs, they are intended for hooking up servo motors, but they would absolutely work for my purposes!

The layout for pins D9 and D10 goes (from left to right): I/O pin, 5V, ground.  Since I wanted the data pin itself to provide the 5V, I chose to make a cable using a 3-pin piece of female header, soldering the red wire connecting to the I/O pin (on the left) and the black wire connecting to the ground pin (on the right).  The center pin has no connection.  You can see my “super fancy” cable on the left.

I know this post isn’t particularly about code, so stay tuned for the next parts of this series:

• Part 1: Remote control camera with CHDK
• Part 2: Wiring it up! [YOU ARE HERE]
• Part 3: Updating the MakerBot Firmware
• Part 4: Updating ReplicatorG
• Part 5: Updating Skeinforge