XBee-MATLAB pt.2

Hello again!

I got a thing to (kind of) work! Here’s the slightly modified loop:

r = fscanf(s);
if (r == 'hi')
fprintf(s, 'hello!');

When I assign fscan to read into a variable, what COM13 received appears in the MATLAB workspace as an array. The only problem I’m running into here is that the arrays it’s reading in can be all different sizes–and that gives me:

Error using == 
Matrix dimensions must agree.

So from here, the next steps would be:

  1. adding a start/end character, or otherwise limiting array sizes
  2. hooking the COM13 XBee back up to the Arduino, and then
  3. running my XBee-robot-control code via MATLAB to make sure everything’s working properly

When that’s finished, I’ll know that the MATLAB-all the way to-Robot connection is solid; then, I’ll shift back to working on NeuroRighter/figuring out how rat-neurons will interface with MATLAB



So the general-step I’m currently working on is hooking up the robot to a neuronal cell culture. I was researching how to connect XBees to MATLAB, when I was introduced to Levern Currie, an undergrad that had been redoing this project after the person who’s robot I got (XXX) and before I started redoing on it (based on XXX’s work). (Does this make sense)? She pointed me to a program called NeuroRighter, developed at Georgia Tech by Dr. Steve Potter (who has asked not to be disturbed by the community).

What is NeuroRighter?

Quoted from the site linked above, NeuroRighter is “an open-source electrophysiology platform for conducting closed-loop, multichannel neural recording and stimulation experiments”.

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Some Notes on CAD


Here are some notes that might prove useful:

  • I’m using OnShape, an online CAD software. I’ve got a free student account (which I think means 10 private “documents”), but there are also other free accounts available (no “private” documents–only public ones).
  • The OnShape document of my current CAD can be found here.
    • To see dimensions, please right-click the “sketch” from the sidebar and choose “show dimensions”. The units are in inches–but please note that some of these are incorrect; refer to this post for notes on upcoming/needed changes.
  • Often, people have already created CAD files you need. One of my go-to’s to search for such things is a website called Thingiverse. (This is where I found the Ultrasonic sensor holders).

This is all I can think of for now, but I’ll update as needed.

Have a good day!

3204 3D Printer: Test Print

Hello friends!

There is a new 3D printer in town! Located in room 3204, this super-cool piece of equipment is a MakerBot Replicator and prints using 1.75mm PLA.

Ideal Settings

(as extrapolated from the example print settings)

Layer height: .2mm
Infill: 10%
Shells: 2
Support: [more on this later]
Raft: generally suggested
Temperature: 215 degrees Celcius
Material: PLA
Transfer data via: USB

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XBee Test Sketch


Hello again!

Here’s the premise: you hit key on keyboard, robot moves in requested direction.

I initially wanted to use the up/down/right/left arrows on they keyboard to control the robot, but those don’t “send” as commands through XTCU, which is the program I’m using to control the XBee hooked up to the computer (thus, the keyboard). So, I’ve opted to use i/k/j/l, respectively, instead (I’m right handed). (Tip: keep track of caps-lock).

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XBee Setup



I’m working with  2 Series 1 actual-antenna XBees and an Arduino MEGA + MEGA sensor shield.

I’ve worked with XBees before, so I was leaning towards using them… but I wasn’t really sure if I’d be able to send packets of data, and received  suggestions to look into something less long-distance for my applications. Turns out it is possible to send packets with XBees! I talked to a couple of people about suggestions for the long-distance thing, and it didn’t seem too big a deal–XBees can be easily programmed to communicate on a different channel, and there are a huge range of options. More on setting up XBees here. I’ve set up the ones I’m using so both can send + receive.

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CAD v2 + Preliminary Schematic


The bottom plate is emphasized here, and the holes along the perimeter are for the HC-SR04 Sensor holders; they will be bolted in. Looking at the bottom view, the four holes in the center are for attachment via spacers to the top plate; this top plate is visible as the gray. Since I didn’t CAD in the spacers, this top plate in the CAD is laying directly atop the bottom one. The large rectangular prisms on either side are stand-ins for the two batteries.

I intend to modify the current designs by adding appropriate holes for wire management in the top plate. This will likely be a second redesign, though. Finally, these plates will be cut out of 3mm-thick plywood via a Laser-Cutter.

Continue reading “CAD v2 + Preliminary Schematic”