MeArm update – Work in progress.

Here’s an update of what we’ve been up to in the last 4 weeks of STEM club.

Team MeArm.

We initially built the excellent MeArm from a phenoptix kit, priced £29.99. It’s a nice robot with 4 degrees of freedom, that can be controlled via Arduino, Rasberry Pi, Beaglebone etc.  We managed to get it working really nicely with a Raspberry Pi and ScratchGPIO, Simon Walter’s excellent version of Scratch for the Pi.   The challenge for the group is to control the arm using Python.  It was suggested to use a Wii Nunchuk, or perhaps a Microsoft Kinect, but early experiments have suggested that keyboard input is challenging enough!

Robots building robots.  Skynet!
Progress on our MeArm build. The kit version is in the background, and our JCB yellow in the foreground.  We’re about 2 weeks away from movement control!

Once the robot is mechanically sound, and the servo positions are set, then we should be able to connect it via I2C using the Adafruit 16 channel Servo I2C board.  Once this is done, then we’ll release the python geeks, and let them run wild with their programming and imagination.


Benchmarking the Pi 2 with Minecraft, TNT

We managed to get hold of a Raspberry Pi Mark2! It is purported to have 6x the performance of the Pi B+ but check the great blog post from Eben Upton about how those benchmarks were calculated.

Naturally we wanted to do our own key benchmarking tests, so we set out to compare the B+ and a Pi 2 together.

When we set up our 8 Raspberry Pi model Bs originally, the STEM crew followed Martin O Hanlon’s excellent Python and Minecraft tutorials and Whaleygeek’s python flashcards and started making some very cool scripts, like auto digging and cubes of bombs on demand.

One of the early challenges was to make a 64, 125 and 1000 block sized cube of TNT and detonate it.  Upon detonation of The Big One(TM), the Pi’s processor load chart would max out, and the fps would drop to about 1 frame per every couple of minutes. Eventually, the Pi would come round again, but it generated a lot of heat from the processor, so much so we thought about using heat sinks.

So – we thought it would be a great empirical benchmark for the new generation of  Pis.  We tried to set up 4 different Pis, with the most up-to date build of Raspbian (but ended updating the A+ and B for ages) , loaded the same script in all of them, and executed them in the most synchronised way we had available (pressing the execute buttons at the same time).  We timed how long it took for the processor load to drop below 50%.

It’s obvious the Pi2 has a great deal more grunt, and the extra processor speed and RAM really contribute to performance. You notice it especially when browsing or watching HTML5 YouTube: it’s a feasible computer replacement whereas the Model B was a tinkering machine or sandbox that you could use, if you were patient.

Our next experiments are to get piplay loaded on and perform some emulator benchmarks, and see if it can be built into one MAME Joystick to rule them all!