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    The Learning Circuit
    sudo Sergeant
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    Felix wants to repurpose a broken MakerBot by putting a USB microscope on it and turning it into a control precision microscope inspection station. He’ll update the electronic innards with a Beaglebone and a Replicape, as well as, change the interface so he can control it with an Atari 2600 joystick. Jason Kridner, cofounder of BeagleBone, joins Ben and Felix as a special guest.



    Jason Kridner, co-founder of Beaglebone, connects with Ben and Felix over Skype.  Jason reassures Felix that he should be able to keep up with the frame capture on the USB camera and get it to his display.  You should be able to take it to a 1080P display and see under the microscope through the micro HDMI. You might be limited to a few frames per second, as opposed to 60 frames per second. When you download the Replicape system firmware it uses the PRU for driving the stepper motor control pulses. The Beaglebone Black has two 32-bit microcontrollers (programmable real-time units), ultra-low latency, RISC cores that run at 200 MHz.  It’s got an additional Cortex M3 microcontroller which is also a 32-bit RISC core.  People are more interested in the PRUs (programmable real-time units) because they provide the lowest possible latency IO pins. They have registers mapped directly to GPIO pins and can access the full peripheral memory.  They also get 5 nano second updates on the I/O pins.  Jason also gives Felix some advice on which Linux operating system to use.

    Ben’s made some custom parts for the gantry and provided a stepper motor so that Felix can assemble the parts. Felix puts the gantry together and attaches the Duratool USB Digital Microscope to the unit. He’ll make some final adjustments but everything seems to be working.  Once the Gantry is pieced together, Felix grabs a solar power supply to include in the project.  It can cough up 24 volts at five amps.

    Felix walks through the printer configuration.  He’s installed Kamikaze and is familiarizing himself with OctoPrint.  He makes some adjustments to the configuration file.  He adds two more limit switches, allowing him to ignore the bed dimensions.  Next, he figures out the device tree overlay to get the Atari 2600 joystick working.  Ben admires the finished build.