BeagleBone USB

I’ve been working on the flight electronics for the 6″ rocket.  One issue is that I’ve got a few peripherals that I want to connect through USB, but the BeagleBone Black only has one USB port.  I’ve been working on connecting them through a USB hub, and have been having some problems.

What I’m trying to connect is an IMU and a GPS.  I can connect each one individually directly to the USB port on the BeagleBone and they basically work.  There is a minor odd issue where I occasionally get spurious characters in the data stream from them.  This would be usable by checking for and throwing out bad data records, but it does make me wonder whether there is a problem with the USB port on the BeagleBone.

Regardless of that, when I connect them through a USB hub I can’t even get that functionality.  They show up in /dev/serial, but I can’t get any data from them.  Looking around on the internet turned up some possible ideas, but nothing conclusive.  It said that the BeagleBone is finicky about which USB hubs it is able to work with.  Maybe if I just get a different USB hub everything will work, but no guarantees.  Also, there was mentioned a problem where a powered hub, if it doesn’t have a protection diode, can feed +5V backwards, which the BeagleBone can’t handle.  It was suggested to use such hubs unpowered, or cut the power wire in the cable between the BeagleBone and the hub.  I tried running with the hub unpowered, but it did’t make a difference.

Here are my possible options for going forward:

  1. For now, just hook up one device directly to the BeagleBone’s USB port.  I’m going to start with them in ride-along mode where I’m not depending on them for anything until I see they can put out good data in flight.  This will remove the problem from the critical path while still getting data from one device at least.
  2. Try out a different USB hub.  I will probably do this eventually.
  3. Communicate with the boards some other way like a direct tty serial line.  I’d rather not bother with this.  USB is so convenient.
  4. Other even more out of the way options like going with a different flight computer.

Pyro-Free Parachute Ejection

I didn’t work on rockets at all during the holiday season, but I’m getting back at it now.  I made some more progress on my pyro-free parachute ejection system for the 6″ rocket.  Before, I had a CO2 cartridge and NOS solenoid that will blow the drogue chute out, and batteries that can supply enough current to open the NOS solenoid.  What was missing was a high power switch that could be controlled by the on-board computer and handle the 10 amps that the NOS solenoid takes.

I ordered a high power solenoid driver from Sparkfun.  I made an oversight in that the solenoid driver takes 5v logic in, but my Beagle Bone can only output 3.3v on its I/O pins.  So I had to make a little low power switch out of a transistor that can be driven by 3.3v and output 5v, which becomes the input to the solenoid driver.

I got everything hooked up and was able to drive the solenoid from batteries with the driver controlled by the Beagle Bone also powered by the same batteries.  I’m using an Any Volt to supply regulated 5v to the Beagle Bone, which also probably provides some brown out protection.

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I did a bunch of puzzles over the holidays, when not doing rockets, which you can see on my work surface.

Stretch Mustang Parachute Ejection Test

I did a ground test on a parachute ejection charge for the stretch mustang.  I started with a quarter gram of black powder and it only pushed the nosecone about halfway out.  I’ll go up to a half gram and test it again.  After that about all that’s left is decoration and launch day pre-flight prep.

[Update] I did another test with a half gram and it worked fine.

More Progress on Stretch Mustang

I epoxied the e-bay bulkhead into place in the Stretch Mustang.  So then I could test fit all of the recovery components inside the rocket, and I’m happy to report they all fit.  There are a few minor odds and ends to finish up.  The only major thing left is painting.

It’s fairly close to being ready to fly.  However, winter is here in the rockies so I don’t know when the next day will be when I feel like braving the weather to go fly.  In theory Northern Colorado Rocketry has launches once a month even through the winter, but they are often cancelled.

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