Brian Ramos

I received the mainboard and began populating one test board by hand.  When I got to the first inductor, I was awed by how awesome the little guy was!

This is an 3.9nH inductor in an 0402 package making to 20×40 thousands of an inch or a little larger than a grain of sand.

Work

Making ringtones for your jailbroken iPhone in Ubuntu is easy using SoundConverter.  I’m going to assuming your iPhone is already jailbroken and you know how to upload files to it (usually with openssh).

First thing to do is make sure the Universe repository is enabled by going to System->Administration->Software Sources and checking “Community-maintained Open Source software (universe)”.

Read more…

Personal iPhone

Yesterday I priced out all the parts for the multilateration system. Nearly everything is available from Digi-Key with the exception of the LNA, an oscillator, and an SMB connector that I have to get from Mouser and an RF splitter from Mini-Circuits. One thing I like about Digi-Key’s website is that they don’t have alot of useless graphics about that just make a site slow. Simple, clean HTML. Nice.

Work

It turns out there was an error on the board that I managed to catch in my final sweep of the board. Now I’m wondering if there are any other unfixed gremlins waiting between the traces to bite me. Oh well, nothing to do but get it in hand and see if it works as expected.

I’ve packaged up the transmitter and sent it our for quote so I’ll be ordering that today as well.

Work

I completed the design for the multilateration system today.  At least I hope I did .  I was quoted at $120 a board which is not bad for quantity 10 with a 5 day turn around.  Here’s what the completed board looks like with all layers turned on.

Completed Multilateration System Board

Next thing to do is generate the bill of materials and order all the parts.  The fun part.

Work

The RF portion is now complete. The component on the left hand side of the image below is a Analog Devices ADC4360 synthesizer running at 870 MHz and serves as the local oscillator to jump down to our first intermediate frequency.

One leg of the output is used to drive the transmitter and the other leg is amplified and split four ways for each of the receivers. The traces for the receivers are laid out such that they’re all the exact same length and thus have the same phase shift. This is critical because our system measures the phase differences between antennas to determine the location of a neighbor and layout differences would produce large offsets in phase.

The ‘X’s there surrounding the traces form a via shield tying the surface ground plane to the internal ground planes and serve to isolate the signal from its surroundings.

Work

A nudge here, a tweak there, and slowly but surely the layout comes together. I’ve removed a couple of things (most notably the logic analyzer connector) to make routing a bit easier and bumped up to a six layer board. Having a header to connect the logic analyzer is a nice to have feature but it was turning the traces into a ball of yarn.

I decided to give the autorouter a chance again because they’re just too many nets. I invariably have to go back and tweak a bunch but at least it give me a starting point. Here’s what it came up with:

I can see a bunch of tweaks that need to happen but it’s not a bad start.

Work

Well I’m back after a two week winter break. It was weird taking so much time off and utterly unproductive so I’m glad to be back at work.

Today I’m working on the main board that the receiver and transmitter boards plug into. This is the board with the ARM, ADC/DAC, and local oscillators.

Here’s the receiver board:

Here’s the transmitter board:

Each board will plug into the main board via the card edge connectors.

Update: 6:15 PM
I’ve got a good start on a main board. I’ve grouped all the related components and started routing the more critical traces. It’s a start!

Work