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Old Jan 19, 2011, 01:19 AM
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Mini-HowTo
Create your own hardware for GPS Triangle Racing

I had hoped that by this time I would have an idiot proof and low cost set of hardware to use for the GPS Triangle Racing. I have the hardware and it’s (relatively) low cost, but it is not idiot proof. I have several times shown up at the field and it did not work. I have a workaround for the main problem, so I am going to reveal what the hardware is and how to build it. Maybe someone out there can find the missing piece that would finally make it work every time without any programming or fussing with keeping the power on between uses. The problem is the GPS module will occasionally lose its programming and revert to its default settings which do not allow it to communicate with the rest of the hardware. According to the GPS module documentation there is a command that can be sent to change the default settings to whatever you want. However that command has not worked for me. Google tells me that this is a common problem. Some of the units will accept the command and some will not. There is no way to tell before you buy it if it will accept the command to change the default settings. I just love like that. If you have a notebook computer and the special harness to program the GPS it is no big deal to reprogram it at the field. If the command to permanently program the GPS worked, none of this would be necessary. Other than that glaring problem, the system works quite well, certainly as well as the original Sky Navigator hardware, although it is not nearly as compact and elegant a solution as the original.

All of the items are readily available and relatively inexpensive. Most modelers will have the skills, tools, and small parts to build this system. Programming the components is the only thing that most people will not have any experience with, however it is very easy to do if you know what commands to send to the components. I will supply the commands you need. I will also supply links to websites explaining the programming if you want to try something different.

First, let me explain what we are trying to do with this hardware. Sky Navigator needs GPS data fed to it in the form of NMEA sentences. It will only accept data at the baud rates of 4800, 9600, and 115200. The 115200 is not really there for data reception, but it can be used if needed. All of the hardware components must be able to operate at the same baud rate. The hardware needed to provide the data to Sky Nav consists of 5 components, 2 in the aircraft and 3 on the ground. The aircraft components consist of a GPS module which receives the GPS data from the Earth orbiting GPS satellites and converts this data into NMEA sentences. The NMEA data is then transferred by wire to a transmitter which transmits the GPS data to the ground. The ground components consist of a receiver to receive the GPS data from the aircraft and a device running the Sky Navigator software (typically an Ipaq PDA). The third ground based device consists of whatever is used to transfer the data from the ground based receiver to the PDA. This can be a serial cable connecting the receiver to the PDA or it can be a Bluetooth device which transmits the data from the ground receiver to the PDA wirelessly.

The largest course we fly is 500m to each turn point so the radio range only needs to be about 1 km. Feeding the data to the PDA as fast as it can be processed should give us the least delay on the real time display. (I know just enough about computers to know I might be completely wrong about this. Please correct me if you know otherwise.) Using the onboard batteries, whatever voltage they may be, would be the most convenient and lightest way to power the airborne components. We want to use a light weight, rechargeable, and readily available battery for the ground components. Sky Navigator only runs on the Windows Mobile operating system, so our display device must run on Window Mobile. Typically, an Ipaq PDA is used for the display device.

I am currently using the Locosys LS20031 GPS receiver shown here: http://www.sparkfun.com/products/8975 . Inside the aircraft this GPS receiver is connected by a homemade wire harness to a voltage regulated breakout board
http://www.adafruit.com/index.php?ma...roducts_id=126 containing an Xbee 900mhz transceiver module http://www.sparkfun.com/products/8975

For the ground based equipment, an identical Xbee 900mhz transceiver module is mounted on a voltage regulated serial board http://www.robotshop.com/technologic...m_campaign=jos A special serial to PDA cable then connects the PDA to the board. Different PDAs use different cables, depending on which proprietary connector they use. A Google search on the model number of your PDA and “serial cable” will usually find the correct cable for your particular PDA. A serial to Bluetooth adaptor could be used in place of the cable but I have not yet spent the time to work out the configuration.

Each of these components requires some programming in order for them to talk to each other and to deliver the required data to the PDA without overwhelming it with data it does not need.

The Xbees are delivered with a baud rate of 9600 which is what I use. The only thing that needs to be programmed in this case is the PAN ID which the modules use to ensure that they only communicate with each other. They are programmed with free software called X-CTU. The software can also be used to see the data stream that is being passed between the Xbees. They are FHSS (Frequency Hopping Spread Spectrum) on the 900mhz band. For programming, you will need a serial cable to connect the Xbee adapter board to your PC. If your pc does not have a 9 pin serial port then you will need a serial to usb adapter cable.

The Locosys GPS module needs to be programmed for baud rate, update rate, and which GPS sentences to send. It is programmable for most any normal baud rate. The position update rate can be set to 1, 4, or 5hz. You can also program which of the 16 available data sentences to send. This programming needs to be put into the nonvolatile memory so that it does not revert to the default values if the backup battery goes dead between uses. This is the part I have not had any luck with.

The free software program RealTerm can be used to program the GPS. Here is a page that discusses programming the module. http://diydrones.com/profiles/blogs/...cosys-gps-with Please read the information on that page to get a feel for how the process goes. The module comes set to 57600 baud rate at 5hz and with more messages turned on than we need. First we need to only send the RMC and GGA messages. Here is the command: $PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0*28

Now that we are only sending 2 types of messages, we can slow down the baud rate to 9600. Here is the command: $PMTK251,9600*17 After we send the command to set the baud rate to 9600, we will get a bunch of gibberish in the display. That is because RealTerm is still set to 57600 and the GPS module is now running at 9600. We need to reset RealTerm to read at 9600.

Now that RealTerm is once again communicating with the module, we can attempt to permanently set it to 9600 baud rate, 5hz update rate, and to only send RMC and GGA sentences. Here is the command to run: $PMTK390,1,5,9600,0,1,0,0,0,1,0,0,0,0,9600*3C I hope you have better luck than I did:

Both the Xbees and the GPS module require 3.3v. That is why the adapter boards with voltage regulators are required. The boards will accept anything between 5 and 16 volts and then regulate that down to 3.3v for the Xbee and GPS module. The ground based adapter with the DB9 connector needs 5v to run the serial connection (also known as RS232). This is automatically provided by the board and is why it requires an input of at least 5v. The airborne Xbee adapter gets its power from the model’s flight battery through any open channel on the model’s receiver or if none are available, it can be Y’ed into any existing channel. It does not draw much power and does not require a signal from the aircraft control system. Please study the information on this page to learn how to program a PAN id into your 2 Xbees so they will only talk to each other. http://www.ladyada.net/make/xbee/configure.html It is surprisingly easy.

When installing the components in the plane, the GPS module needs a clear view of the sky. Like most of the radio stuff we use, it can see through fiberglass and wood, but not carbon fiber or metals. Install the Xbee with its antenna at least 3 inches away from any other radio components to avoid any interference with the plane’s control system. This distance is not scientific; it is just what I have found to work so far. In a 1/3 scale sailplane, that is not a problem, but for smaller planes, you may have to get creative on how servo wires are routed in order to keep them away from the Xbee. In any case, be sure to do a range check with everything turned on before flying.

The Sky Navigator software can be downloaded from the Icare Sky Nav page: http://www.icare-rc.com/skynavigator.htm or the Tun Modellbau page: http://www.tun.ch/product_info.php?p...f22cb33f76a51f

The user manual is also available from both sites. The manual on the Icare site is in English.

The software will load onto your PDA in demo mode. In order to activate the software you must buy a license from this page which is linked from the previous Tun Modellbau site: http://www.skynavigator.ch/PayPalShop/SkyNavShop.html You really only need the basic module although the others can be nice to have, especially the English module.

I am not an electrical engineer, nor do I play one on the internet. I am sure there are better and/or cheaper components that could be used, but this is what I have found that was readily available and reasonably priced (to me). I have been using them for the past 4 months and they seem to work as well as the original components from Sky Navigator. However, the Sky Nav hardware is smaller and more elegant. Also, their hardware is legal in Europe where mine is not. The Xbees are available in other frequencies but I will leave it to others more knowledgeable than myself to decide if those versions are appropriate. Please feel free to use this information to build your own system or design and build a better system. I do not have the time or the desire to be in the electronics business at the moment, so I invite anyone interested to supply these (or better) systems for fun or profit. If there is enough demand and no one else comes forward to supply these systems I will do a small run but I would much prefer to spend my time flying and building.

If you have questions, please post them to the thread instead of asking me directly. It is quite likely that I will not know the answer (remember, this is not my area of expertise). I am sure that someone out there will know the answer and then everyone can benefit from the question. Also, if I have given any bad information please correct me so we can all benefit from my mistake.

List of components:
Your choice of PDA
Serial cable for PDA
Locosys LS200031 GPS module
Two 900mhz Xbee Pros
Voltage regulated Xbee breakout board
Voltage regulated Xbee serial breakout board
Battery to power Xbee serial board
4 wire cable and connectors
FTDI cable or serial cable
Single wire and connectors

I will try to take some pictures of my system and post them later this week. In the mean time, a lot can be learned from visiting the links to the components and then following the links on those web pages to more information.

Rick
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Old Jan 19, 2011, 12:35 PM
yyz
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Rick,

First off, thank you so very much for taking the time, effort and money to get this off the ground in the US. All of us passively waiting and watching owe you a debt of gratitude, for sure.

As you mentioned last weekend, this particular GPS "losing" its setting is a pain in the butt. I've worked extensively with this brand of GPS receiver (Swiss-made) and they are known to be reliable and in general "good workers":

http://www.sparkfun.com/products/9566

and they are only $20 more than the one you are currently using. I have one that you can borrow if you'd like to do some experimentation. The wiring interface is basically what you have for the other GPS receiver.

While I believe people are still trying to wrap their minds around this style of flying, your efforts have effectively destroyed the "It's too expensive" argument. For a couple of hundred bucks you have a setup that allows you to record your flights, fly your planes in a manner consistent with their full-scale counterparts (which is incredibly fun), compete with your buddies if that's your thing, and optionally post your flights to the Internet to record your epic flights for the rest of us to see, replay and admire.

Speaking of which, someone posted a message on one of the German soaring groups yesterday the following notice (translated by Google Chrome):

Quote:
Launched: ModelGliding-OLC
Hi,
the alpha version of ModelGliding-OLC on the net: http://rc.onlinecontest.org/ .
For everyone who participate, there are some important things to know:
a) Participation is free
b) The participation is permitted only to natural persons who have registered with their full name and address in the registration form. Particularly important is the phone number, as we will check each participant to a call, whether he is for he has answered (ie, a MacGyver with a fantasy-Telefonnummmer would be deleted instantly).
c) The uploaded files must meet standard IGC, which relates in particular to the completed header
d) Martin Thoma has created a conversion software that can convert all the popular formats in the Modellsegeflug in gliding sports used IGC format. Details on the RC-OLC homepage.
e) Since yes is not a season for the moment and will meet from last year is not the message window (they are not measured) can be modified using a text editor in the header's date (most current date of the flight booking). But the pilot's comment must be pure that it is a test example with a modified date is the correct date was DD.MM.YY
f) An assessment of the flights carried out first by the rules of the OLC for paragliders. After completion of a phase of experience is then converted to special rules and model glider flights in the system nachgewertet (if it comes to 'real' flights).
g) The communication is handled here through RC network, where the questions / answers of general interest.
Specific questions, please contact RC@onlinecontest.org mail.
Good luck!
Bye - Reiner
http://www.rc-network.de/forum/showt...=1#post2162778

For some background on the OLC, please see the following:

http://translate.google.com/translat...e%2Findex.html

Mike
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Old Jan 19, 2011, 04:07 PM
yyz
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A sample flight

This is what a sample GPS triangle flight looks like. The site is still in alpha testing so please no complaints about "this or that link being broken..."
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Old Jan 19, 2011, 10:14 PM
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Quote:
Originally Posted by yyz View Post
As you mentioned last weekend, this particular GPS "losing" its setting is a pain in the butt. I've worked extensively with this brand of GPS receiver (Swiss-made) and they are known to be reliable and in general "good workers":

http://www.sparkfun.com/products/9566

and they are only $20 more than the one you are currently using. I have one that you can borrow if you'd like to do some experimentation. The wiring interface is basically what you have for the other GPS receiver.

Mike
I looked at that gps unit when deciding what to start with and did not use it because of the cost. I started with the EM-406 and then went to the LS20031 to get a faster update rate. Basically, I started with the cheapest unit I could find (that I could understand) and have been working my way up the cost ladder. I didn't want to start with the more expensive units and then find out later that a cheaper unit would have worked just as well.

I have spent a couple of hours today studying the manual, downloading the configuration software, and reading the configuration software manual. I am still not convinced I can program it to just send the GGA message. All of the examples of programming I could find are setting the ubx messages, not the NMEA messages. Since you have used these, can you program it to only send the GGA message at 9600 baud rate? And then put that configuration into the non volatile memory? I do not see any mention of any kind of backup battery or capacitor so I assume if it is not stored in the non volatile memory it will revert to the default values upon disconnection from the pc and/or power source.

Rick
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Old Jan 20, 2011, 11:38 AM
yyz
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Quote:
Originally Posted by rshelby View Post
I looked at that gps unit when deciding what to start with and did not use it because of the cost. I started with the EM-406 and then went to the LS20031 to get a faster update rate. Basically, I started with the cheapest unit I could find (that I could understand) and have been working my way up the cost ladder. I didn't want to start with the more expensive units and then find out later that a cheaper unit would have worked just as well.

I have spent a couple of hours today studying the manual, downloading the configuration software, and reading the configuration software manual. I am still not convinced I can program it to just send the GGA message. All of the examples of programming I could find are setting the ubx messages, not the NMEA messages. Since you have used these, can you program it to only send the GGA message at 9600 baud rate? And then put that configuration into the non volatile memory? I do not see any mention of any kind of backup battery or capacitor so I assume if it is not stored in the non volatile memory it will revert to the default values upon disconnection from the pc and/or power source.

Rick
Rick,

The ublox gps receivers use a really nice graphical UI that allows you to change all of the configuration of the gps. You can get it here:

http://www.u-blox.com/en/evaluation-.../u-center.html

If you decide to try one, let me know and I'll send you one of mine.

Mike

ps: yes, I'll try and configure one tonight for that specific nmea message
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Old Jan 21, 2011, 02:06 AM
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Here are some pictures of the hardware I am using now. You may notice that some of it is not what I linked to in the first post although it still serves the same function. I will build the next set from the components linked to earlier. Once I get them and start the assembly, I will take pictures to show the entire process. The messy looking harness is what I use for programming gps modules and xbees. The red board is a dual voltage regulator that provides both 5v and 3v output. I hope I can come up with a procedure and a set of components such that builders will not need any extra components or harnesses in order to do the programming since this can add $50 to the cost.
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Old Jan 30, 2011, 09:29 AM
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Quick question:

When you say PDA in these posts, are we talking about a device like a pocket PC, Palm Pilot, a dedicated device for this application? Or are we talking PDA as a generalized term meaning smart phones like Android, iPhone, etc?

tk
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Old Jan 30, 2011, 12:28 PM
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Tom,

Sky Navigator runs on the Windows Mobile operating system. So any device that runs on Windows Mobile can run the Sky Nav software. Typically the Ipaq PDA has been used because it had the largest screen. Ipaqs are used in full scale sailplanes to run their navigation software so I suspect that is why Sky Nav was written for Windows Mobile. I have heard that the Ipaq 310 has the best screen for this type of use. But don't take my word for it as I am no expert. There is a lot of information on this full scale soaring site: http://www.cumulus-soaring.com/pda.htm

I should note that the software allows the user to change the colors of the display. That is something I need to play with to see if there is a better combination of colors for the display on my particular PDA which is an Ipaq 4355. Perhaps some of our European friends who have been using the software could let us know if they have found a better color combination than the default.

Rick
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Old Jan 30, 2011, 01:49 PM
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Thanks, Rick!

Another device to take to the field LOL!

tom
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Old Jan 30, 2011, 10:29 PM
yyz
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Quote:
Originally Posted by tkallev View Post
Thanks, Rick!

Another device to take to the field LOL!

tom
I thought the very same thing, Tom, as I forked out the money for something else to accidentally leave at home Once you see the whole setup, including Sky Navigator on the PDA, you'll be glad you jumped in.

When this style of flying gets a foothold in the US, you'll start seeing more options that compete with Sky Navigator on a PDA running Windows (eg, iPhone, etc).

From what I've read, the fellow that developed the software did it on his own time just to get something up and running so they could race scale sailplanes, which is admirable.

There are a lot of smart folks in the soaring rcgroups forums that could replicate this effort without a huge amount of effort or financing and give users a wider choice of hardware.

Mike
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Old Jan 30, 2011, 11:48 PM
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That's why I'm following this thread so closely ... now where do you get a good buy on these PDAs? I really don't want to drop $300-$500 on something that in my neck of the woods will only get used two or three weekends a year.

tk
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Old Jan 31, 2011, 12:03 AM
yyz
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Originally Posted by tkallev View Post
That's why I'm following this thread so closely ... now where do you get a good buy on these PDAs? I really don't want to drop $300-$500 on something that in my neck of the woods will only get used two or three weekends a year.

tk
You won't need to spend that much. I bought an HP iPaq on ebay for around $200. I doesn't have a serial port like the one in the picture Rick posted.

Rick, which model of iPaq Pocket PC are you using?

Mike
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Old Jan 31, 2011, 01:48 AM
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My Ipaq 4355 was given to me by someone at work who always has to have the latest electronic gadget. It had been boxed up in his garage ever since it was made obsolete (according to him) by whatever came on the market 6 weeks after he bought it. The devices I will use for the next 2 systems I build are a pair of Audiovox 6601 Pocket PC mobile phones. Basically they are an Ipaq that is also a mobile phone. Here is a link to where I bought them: http://www.surpluscomputers.com/3504...01-pocket.html

The "Grade C" rating means that they are very used. The screens look terrible from where they have been scratched by the stylus. Amazingly, once they are on, you can see right through most of the scratches. I actually bought 3 of them, but will only use 2. The 3rd one's screen is just too badly scratched and it's battery won't hold a charge. The batteries are typically $10 - $20. I didn't expect any of the batteries to hold a charge, but the other 2 seem to be okay so far.

Rick
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Old Jan 31, 2011, 07:36 PM
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hi Rick,

Hoping you can help - I have one of the original Skynavigators - and want to use a USB Ipaq instead of the proprietary ipaq plug - any ideas if the output from the reciever to the IPAQ can be wired through USB?

With thanks
Henryk
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Old Jan 31, 2011, 10:29 PM
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Originally Posted by henrykk View Post
hi Rick,

Hoping you can help - I have one of the original Skynavigators - and want to use a USB Ipaq instead of the proprietary ipaq plug - any ideas if the output from the reciever to the IPAQ can be wired through USB?

With thanks
Henryk

I do not think that would work. The first connection I tried between the ground receiver and the Ipaq was through the USB cord that came with my Ipaq 4355. I plugged the cord into this breakout board for the Xbee http://www.robotshop.com/parallax-us...m_campaign=jos

It did not transfer any data to the Ipaq. It does do a nice job of transfering data to my PC however. I now use it for programming the Xbees with the PC. Mike (yyz) told me it did not work with the PDA because the PDA doesn't have the necessary USB serial port in its operating system. Please correct me if I got that wrong, Mike.

Rick
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