Hi Guys. I'm new here so go easy eh!

Inspired by THAT high altitude glider guy years ago Ive finally gone and designed a pcb.

I didn't bother posting before I got the pcb's as I'm sure there are heaps of people with many many great ideas that never become reality for one reason or another & I didn't want to add to the list!

The boards came back last week & with all the excitement I thought I would post on here & get ye guys to critique it!

The board is 10cm by 4cm. I guess I could have made it smaller but I wanted to space things out in case I need to rewire/cut etc. I think(?) it should be small enough for a glider

Its a 4 layer board with some nice gold flash.

Some of the components are from sparkfun; gyros & accelerometers. The rest are microchip & maxim stuff.

It has a PIC18F8720. Should have gone bigger but I have ten samples already & I've used it before & have a nice compiler for it & the microchip ICD.
2 Axis Gyro
Compass
3 Axis Accelerometer
GPS
Serial port
Level shifter 3v/5v
Short range wireless, 10meters
Some ADC & DAC's
5 Servo O/Ps

I put an expandable SPI port so I can put some cheapo boards on with some extras. I got some SD card carriers in the mail so Ill put one on I recon.

I got the surface mount air-gun in the post yesterday so I'll start assembly tomorrow evening.

What do ye think?
I've tried to attach a picture but since this is my 1st post I don't know if it will come out ok.

I've gotten a two friends on board; one has the long range comms sorted & is a massive inspiration, the other is a good programmer. Should be fun!

Cheers,
Vince.

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Looking good, Vince! Can you explain some of your decisions, such as the use of the older style serial port, only two gyros, what you're doing with the short range wireless, and how the GPS connects?
Congrats on getting this far, I look forward to seeing your progress as things develop! Where abouts in Aus are you?
Hey Chris. The serial port was just chucked on the so I can interface to hyperlynx easily. No other reason really.

Two gyros onboard & i'll probably end up mounting one more vertically on the expansion port on the read of the pcb. I was hoping initially for testing to use the compass for simple heading info while the x/y gyros took care of the rest.

The short range wireless is for use during the preflight & ground testing where I can put the long range comms into shutdown to conserve battery. Least that's the initial idea anyway.

If you look at the large blank area on the pcb there will be a connector for the GHS soldered on there. I had two older GPS modules that I thought would be fine & since I payed for them years ago its somewhere to start.

Hi Nick,
I'm in Canberra.

I recon I'll probably end up making a bit of a stack of boards with an SPI interface running from board to board. It would be nice to have an SD card and a few other bits on there too.
wow great board. You may add any small connector (FTDI / microphone twin connector) to replace the bulky DB9 connector. Can save the cost of max232 and db9 connector. How u r going to proceed on its code , any rtos stuff or any multitasking.
Is there any google code page u have for ur development code?
Please update on ur progress. Great work keep it up.
Unless your compass is a three-axis tilt-compensated magnetometer, you'll find that it's unreliable in the air. If you have a good 5Hz GPS, it will give you much more accurate heading info.
Hi guys,
just a small update. The PIC is installed & talking to the computer. I've been a bit busy but should have some more chips on there in the next few days.
I should really start a page of some description with code etc on there. Anyone have any ideas where to post all that stuff?
Cheers
Google Code. Or on your personal page here at DIY Drones....
Congrats. You will find that you actually need 3 axis gyros even if you don't use them for heading. For exampe the equation for roll is comprised of all three body rates (ie gyros). Good luck.
Hey Ryan,
As I'm a total noob to all this its been great to some degree as I've learned heaps over the past few weeks!
I think I will build up a second board with just a gyro on there & I can talk to it over the SPI port & mount the board at right angles to the other one. Least then I will have the 3 axis covered.
I might even use the 2nd board as a dedicated communications board too.
People are talking about 3 axis magnetometers. Would a 2 axis one suffice when combined with the 3 axis gyro setup?
Cheers guys.
Has anyone taken a serious look at the ocean-server AHRS for $249
http://store.oceanserver-store.com/os3axdico2.html

Dave
Hey Dave,
I have a 2 axis compass on the pcb. What are the benefits of a 3 axis one?
Dave, it's described as a "tilt-compensate digital compass", rather than an AHRS. Not sure what the difference is, but they're definitely not selling it as a full IMU/AHRS.

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