Paul Cox Notes

Paul Cox Build Log

TODO

TODO LIST

Num	Name	Notes	Priority	Status
1	Get foam plane flying	Electronics mostly installed, need to hook up servos	x	In Progress
2	Paparazzi Documentation	Started outlining here	x	Started
3	Test Overo/Tiny SPI communication	Interface board built, need to configure sw	x	In Progress
4	Design Tiny with Overo	Will probably altium or orcad	x	Prelim
5	Figure out what I can do for EMAV	x	x	x
6	Design Tiny++	.1" headers, four layers, cost reduced BOM, IMU?, etc	x	Not Started

Jan 2010

Had to pack up all my stuff this summer and just now starting to get back into UAVing. First on the list is to get a plane in the air. I brought most my electronics with me, and the lab is letting me use a foam plane so I should be flying soon. I'm also hoping to start on quadrotors so I can get more familiar with them and help document it. Other things on the task list: Design a tiny with an overo SPI connection.

Nov 2008 - Jan 2009

Installing Software on Ubuntu Intrepid Ibex 8.10

Used CVS to download "paparazzi3". also discovered Booz guys are using svn and that repository is called "paparazzi4".

Read the wiki multiple times through, built everything acording to instructions, and fired off the program which seems to run in simulator mode, although

I'm currently not seeing any action when I hit the "Launch" button. I probably haven't read something important somewhere...

Gather hardware:

Looked at the hardware designs in CVS to see if I wanted to customize a design or build one of the "released" designs. In summary, the current things

folks are building and using are:

Autopilots

• • Tiny 1.3 - ARM processor and GPS on 4 layer PCB with 0402. Benefits: smaller and 4 layers is more reliable Drawbacks: Design is older and has

evolved so there are some missing feature and maybe some issues (Insert more specifics here as I learn them)

• • Tiny 2.11 - ARM processor and GPS on 2 layer PCB with 0603 SMT devices.
  • TWOG - Tiny 2.11 without GPS. I assume people want to branch out and use different GPS and not just the u-blox stuff. Also I see mention that some

people want to mount GPS hardware some place different on their airframe than where the autopilot resides.

• • Booz - Some very exciting quadrotor developments. HW Design not checked yet as there's some errata that someone feels like needs to be fixed before it

is commited.

Sensors

• • Single Axis IR - For two Melexis thermopiles
  • Dual Axis IR - For four Melexis thermopiles
  • GPS board - A PCB to hold just a GPS and an antenna. For use with TWOG

Looked at how much to have the PCBs fab'ed by quick turn board house, but unless you order 25 or more PCBs you're better off buying from the listed

vendors. I went with PPZUAV:

• single IR PCB $8
• Dual IR PCB $8
• Tiny 1.3 PCB $9.95
• Tiny 2.11 PCB $5

$6.80 shipping (California to Washington)

I check first to make sure all was in stock, and David replied that it was. Order took a couple days to process and a few days for the post office to

deliver the priority lettter. PCBs arrived in a little padded envelope and even though I knew the dimensions before, I was surprised at how small they

are in the flesh.

Components were mostly from Digikey: TI DC/DC was only available in SMT and no shotkeys.

Complete List: (insert spreadsheet here)

Mouser had the switching DC/DC in through-hole and shotky diode so put in an order with them as well:

Of note: Looked for GPS modules and antenna and found some items of interest. A Tyco GPS module with a built in antenna for $60 []. Also antenna [].

Different center frequencies are available 1575 MHz and 1579 MHz, but googling seems to show that 1575 is the main GPS freq. Not sure what 1579 is useful

for, but it kinda looks like the one paparazzi recommends from their testing is centered at 1579 so I must be missing something.

Complete List: (insert spreadsheet here)

While waiting for all the hw to arrive, built a wireless GPS device:

Main components:

Wireless modem: XBee Pro 802.15.4 (XBP-24-AUI) GPS: Battery: 2S Lipo (gutted Axim x50v battery, rewired from parallel to series) Antenna: Some rpsma? wifi antenna I had laying around with a u.fl connector/pigtail.

Other components TI DC/DC converter (same as used on tiny) 100uF tantalum capacitor (TI DC/DC conv requires this on the input) SPDT toggle switch Samtec mating connector for GPS kynar wire plastic box and some thin model plywood for a case

Receiver is another XBee Pro in a USB carrier board. The XBee Pro has a wire antenna (XBP-24-?UI). Looking back I should have ordered with the RP-SMA so

I can put some coax on there to a big honkin' antenna to improve range.

Build process: Main obstacle here is the fine pitch connector on the GPS module.

XBee Pro and the GPS module are 3.3V devices. For the TI DC/DC used on Tiny to produce 3.3V a 1.87kOhm resistor is needed an input capacitor of 100uF is

needed. I wired up all these components

Bring up process:

Getting things talking was suprisingly easy. XBee devices come pre-programmed and configured for transparent mode at 9600bps. There's destination and

source addresses and all sorts of configurable stuff, but out of the box two XBee will just find and talk to each other (great job guys!). Transparent

mode basically means that both the devices send traffic to each other transparently, so essentially the end devices don't need to know anything since the

XBees just look like a wire.

The GPS module provides NMEA data at 4800 baud so I needed to reconfigure the XBees for that lower baud rate (I may not have needed to do both, but I did

anyways). Doing that involves getting out of transparent mode and into command mode (done by sending characters "+++") at which point a few "AT" commands

are used to change the rate and save the setting to non-volatile memory.

By the way, Digi also makes a windows application available called "X-CTU" which is very useful. It will test communication with your XBee device,

read/write the module's settings, and has two other very useful modes: A range test mode where the the Xbee on the far side of the link has had it's

RX/TX pins wired together for loopback and signal strength is displayed; and a terminal emulator that works nicely (I had a heck of a time finding a good

terminal program that worked with my COM26 device, looked good, and was easy to use. No matter how much .ini hacking I did I couldn't get teraterm to

look beyond 4 ports).

So first to validate that my DC/DC is providing power and the GPS works, I hooked up a GPS to a serial/USB converter (from acroname) to the GPS RX/TX

pins and plugged the USB cable into my laptop. Turn on power and sure enough, lots of NMEA looking stuff spews forth. Next rewired the GPS to the XBee

and plugged the USB/XBee device into the laptop and, voila, same data shows up as before but this time the GPS device is totally wireless.

Now I wanted to get more than just a bunch of NMEA strings on a terminal window, I wanted to see the position in google earth or google maps. I bought

the plus version of google earth and had used it with my Garmin Etrex Vista successfully, but it turns out that it doesn't work directly with an NMEA COM

port based device (at least for me). Instead, there are a number of folks out there that provide little command line programs that open the com port and

crank the data out in xml via http socket. Google earth can open a network location.

Tiny v2.11 Assembly Process

Once all parts arrive: sorting components and getting BOM and component placement references ready for use. Wiki has all this info nicely laid out.

• PCB silkscreen and wiki image () have LED1 and LED2 reversed. Not sure which is correct yet.

Since there's more components on the CPU side, that's the side I populate first. Starting with smallest components to largest makes assembly the fastest.

Once all components mounted and the input power wires are soldered, time to apply power. I used a benchtop power supply so I could monitor current.

With a voltage input of 7.0V, current should be around 50? mA.

Now attach IR sensor boards and USB connector along with wires for other interfaces (serial, download, rc receiver -- I'm waiting before doing servo

wires to keep things tidy until later)

First order of business is to download USB bootloader over the serial port. This uses the "Download" serial port so you have to disable the GPS, but I

hadn't populated it yet so didn't have to bother with disabling it.

Now that there's a USB bootloader, downloading code into Tiny just requires plugging in the USB cable, powering up, and sending the code (which is either

done with a "make" command or pressing the "Upload" button in Paparazzi Center.

Now to run a simple program: LED test. Some nice instructions on getting this going are [here].

All goes well and three LEDs are blinking.

Now download autopilot code. A direct connection of the serial port to a USB-serial adapter plugged into my PC relays the telemetry data. Firing

Paparazzi Center and executing the session "Flight USB-serial@9600" shows battery voltage so I'm up and running.

Now I attach the IR boards

Mounting

Messy Hardware

Mounted Tiny

Mounted Tiny

Things are getting sloppy and afraid something will short and fry, so it's time to mount things to get things under control. I had some plastic cases that some lenses came in which happen to be just the right size. Tiny, my 2S lipo, and an XBee fit in one side perfectly, and the other side can be used for extra wires, the USB connector, power switch, and the RC Receiver. The IR sensors are hot-glued on the exterior using a little balsa. Probably won't be useful when it comes time to fly, but it's compact and sturdy which is what I need until I'm ready to start thinking about flying...

Configuration

I started with the funjet1.xml airframe file because I read others use that with the Tiny2.11. I don't plan to use a dual elevon plane (instead will do a

standard rudder/elevator/ailerons setup) so will have to make lots of changes -- not a bad way to learn how things work... The

Airframe Configuration page is a great help here.

• • Battery voltage - The default looks to be setup for a 3S battery and perhaps my resistor devider resistors aren't the right values, so GCS reports

incorrect battery voltage. Instead of hunting through the code I vary the voltage on my power supply, watch the output, and empiracally find the correct

values to set:

<section name="BAT">

<define name="MILLIAMP_PER_PERCENT" value="0.86"/>
<define name="VOLTAGE_ADC_A" value="0.0245"/>
<define name="VOLTAGE_ADC_B" value="0.1"/>
<define name="VoltageOfAdc(adc)" value ="(VOLTAGE_ADC_A * adc + VOLTAGE_ADC_B)"/>
<define name="CATASTROPHIC_BAT_LEVEL" value="6.4" unit="V"/>
<define name="CRITIC_BAT_LEVEL" value="6.8" unit="V"/>
<define name="LOW_BAT_LEVEL" value="7.0" unit="V"/>
<define name="MAX_BAT_LEVEL" value="8.4" unit="V"/>

</section>

• • IR:
    • Mode - I change from to tilted to aligned mode because tilted mode seems weird.

remove:

 <define name="HORIZ_SENSOR_TILTED" value="1"/>

add:

 <define name="HORIZ_SENSOR_ALIGNED" value="1"/>

• • • Neutrals - The "cupboard test" shows the neutral values are pretty close already.

• • • Direction - Tilting the sytem around, I see that one of the axes is reversed so I set IR2_SIGN and TOP_SIGN values accordingly:

insert here

• • GPS - For LEA-5H u-blox module: add -DGPS_USE_LATLONG in makefile portion of airframe xml file as per instructions on wiki []. I still get some error

messages, but they stop after a few seconds and all seems to work.