Hi there! We're still hard at work on the Soundplane A. We have been busily designing parts and putting them together, and it's starting to resemble finished hardware. Let's take a look...
I've recently taken delivery of the flex circuits that are the Soundplane's carrier antennas—basically its only moving parts. There will be four antennas on the Soundplane with 16 carriers each, for a total horizontal resolution of 64 taxels. Here's one of the antennas in closeup.
This was kind of an unusual design because the shapes of the antennas are so critical. Though everyone seems to use it for making PCBs, Eagle would not really, as far as I could tell, have been a good tool for drawing this kind of thing. Adobe Illustrator was, and I already had it. So I looked around for a way to convert Illustrator files to Gerber, which is the format the circuit board people use. I was in luck! Some guy in Seattle had already written a Perl script for this purpose called pdf2gerb. I modified it slightly to output rectangular line ends instead of circular ones, and made some Gerber RS-274X files, hooray. Another open-source tool, gerbv, lets me inspect the Gerber files before I send them off. I was able to get gerbv compiling pretty quickly using Fink on Mac OS X.
Typically, flex circuits are little guys, stuffed into your camera or cell phone. These antennas are considered really big pieces for the process and consequently a little expensive. But flex is the only way I found to reproduce them with the very close tolerances we need. Our prototypes have been made by IPC Calflex in California.
In this picture you can see all the carriers from the top. Instead of the veneer surface we are developing, I have covered the carriers with a matte finish plastic. Now that I see it, I like the look of the Soundplane this way, and I'm guessing that some people will want this as an option.
In the background you can see one of the ubiquitous blue tarps that we Cascadians use as shelter during the winter months.
Here's the flex from the side, bringing the carriers up from under the pickup board that amplifies the received signals and sends them to the DSP. It's a really compact design and there's no way we could have pulled it off without the FFC (flexible flat circuits) and ZIF connectors.
And meanwhile at Brian's, here's the first rev of the DSP board itself, hooked up to a logic analyzer for testing. Our board is based around a Texas Instruments CPU with a combination of high bandwidth and low power. Internal to the Soundplane we have 32 carrier signals and 16 pickups signals all running at around 60 kHz. That's around 50 Mb per second. And amazingly, we will be able to run off USB power if things go according to plan. We have a DC jack on the prototype, in case things don't.
For assembling these boards, we are working with Schippers and Crew here in Seattle. Friendly, fast turnaround, quality work—I've been really impressed. And, their shop is just a short bike ride from my house.
Brian has checked out all of the board's subsystems now, and is making the rev.2 design. When we get those boards back, we can start writing the firmware that will calculate the pressure grids and send them over USB.
The analyzer itself is a pretty cool product. Made by Saleae (which I have no idea how to pronounce), it looks very approachable, but is a powerful tool for the serious hardware hacker. Its software is Windows-only for now, but they claim Mac and Linux support are coming soon.
There are a ton of details, but they are all coming together. The case design is getting a minor revision, and the metal plate that reinforces the USB jack needs to be finalized after the DSP board is finalized. And I'm still working on getting the veneer surface just right, but that's probably another post in itself. Stay tuned for more, including more DIY info and previews of our first synth software, coming soon.