Dedicated audio server for ROV using Pi and Wolfson Audio board


#1


Hello,

Continuing my previous post on adding streaming audio from the ROV using icecast and darkice2 I have tried again! This time using a raspberry pi and a wolfson sound card that plugs in to the pi. It looks pretty good so far. The bad audio latency and buffer underrun problems I had before trying to pull from the webcam mic with the beaglebone are gone, and I boosted up the quality to 44khz and 128kbit. It will need a test streaming some music from an audio input like a CD player or Ipod though to really see what's going on but the delay is down to a little over 1 second from whistling in my kitchen to the onboard mics picking it up. I'm no vanderbelt so there could a nicer solution than adding a 2nd computer just for audio....but I really want audio for a more immersive driving experience for kids!

So how would you add this to the ROV? Well, if you shorten up the USB cable and clean things up a bit there should be plenty of room under the camera. I will have to do a fit test to see though. We will also need a switch or multi-port homeplug adapter so this audio server can run alongside the beaglebone black on the network. Mark has parts for this and says it should not be a problem. Eventually the ROV will be a whole computer network of it's own with multiple cameras on the network along side the control server and hopefully audio too if everything goes well!

To start with I would just want to use the onboard mics for simplicity sake, but then we could connect this to a hydrophone with some extra wires going through the endcap. So there's not much to see yet, but I am happy with this test and getting the darkice stuff to compile and get data from the wolfson mems microphones.

Thanks to Mark for parts.

-Matt



#2

Matt, I've been thinking about the hydrophone and the adapter for the ROV. Would it be better to build a water tight coupler for accessory attachments? I actually think this is the best way to go. Can we standardize an accessory line and water tight plug? This would allow for hydrophones, CTDs, and other payloads to be plug and play for the kit.

Thoughts? I'll see what small water tight wire couplers are cheaply available and the best ones dimension wise to attach to the ROV. I think hardwiring an additional bit of hardware would be fine at first, but in the long run, a multi-purpose external expansion port would be the better design decision.

Jim


#3

Hello Jim,

That does sound good. I know Mark and Tony are testing a detachable tether design using some pins covered in toilet bowl wax with a rubber cover and some mini hose clamps. Eric has talked about how it would be cool to try silly putty as well for making water proof connectors. Other than that I am not sure about cheap connectors that would work well. Adding a pass through connector on the end cap with pins exposed that you solder to and cover with wax has also been talked about for Marks right angle DB25 idea that would remove the wiring harness, prevent water wicking in to the ROV, and make endcap wire maintenance a possibility by removing the wax.

If you find a good part fitting the idea or another technique please post it! I think it would be cool to be able to swap between payloads for sure. Maybe not instant payload switching but at least not involving soldering would be nice.

-Matt


#4

Build-a-Hydrophone

They are using liquid-tight cord grip and compression nut.

http://www.coseetek.net/programs/TTE/acoustics/


#5

Hi Mark, Yeah, I actually built this exact one for my first prototype. I was thinking about a multi-conductor water tight jack for n-number of payload options. Say 9-pin, 3.3 and 5V supplies, then a few analog and digital signal lines. Thanks for the link.


#6

Try PEX connectors and see what you can do! Watching this closely!


#7

This looks great!