Re: R-DAS I2C Bus

For capturing I2C you can't beat milksop. It's really easy to use and the interface for the parallel port is simple. It will capture all I2C traffic

used to work but seems to be down, maybe it's moved or maybe it's died, not used it for a while.

try this

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and more specifically

"Mjolinor" skrev i melding news:Gp8Zb.77$m47.7@newsfe1-win...

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Thank you for this link, I'll download it and hook it up. But there is one problem..

I dont own a orignal gps module, so I have no traffic to analyze. I want to build my own module and hook it up with the I2C bus in the R-DAS. So if someone out there with a R-DAS and a gps module could capture some traffic and try to localize wich adresses and what coding is used between the components, I would be really happy.

Regards Bernt-Johan Bergshaven

to

Well, now I'm REALLY confused. You want to build your own GPS Engine?!?

I'm thinking that you don't understand exactly what a GPS engine is... it is a combination of very complex time keeping doo-dads, a microprocessor, extremely complex algorithms, internal (or optionally external) antenna's, etc, etc.

In addition... there are US government (and some International) regulations on 'blanking' that MUST be observed if you don't wanna find your butt on a base in Cuba... that is, if the GPS module is going above a certain altitude AND a velocity faster than 'X' then the GPS unit

Trust me... you want to purchase your GPS engine... I like the Garmin variety.

As far as I know, the information coming from the GPS (no matter what module you decide to use) is straight serial... there is no 'address'. I know this is true for Garmin... I know this is true for *ALL* NEMA compliant GPS receivers.

If you want to CONVERT the information that the GPS unit spits out into the IC2 bus protocol, then the addressing would be assigned during YOUR conversion. I'd recommend a PIC for this operation.

Since you want to build your own GPS module, I would suggest that;

1. You choose which GPS engine you will use.
2. Study the NEMA protocols.
3. Examine the flavour of the GPS engine NEMA protocols that you've chosen.
4. Study the IC2 bus architecture
5. Study (a suitable) Microcontroller language (RICS \ PIC recommended).
6. Pick a programming language and study it. (In your case, BASIC).
7. Learn to live without friends or social life.
8. Learn to like alcohol... yes... the dry Martini is your friend. ;)

"Mark" skrev i melding news:cAWZb.3313$ snipped-for-privacy@newsread2.news.pas.earthlink.net...

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chosen.

Okey, sorry If I have been unclear in certain points, and let me clear it out.

I have a GPS ( Magellan Colortrack), I want to use the circuit board, and antenna and all the other things needed to have this gps working. This I want to put inside a rocket, and hook it up with the data collector ( R-DAS ). So far okey? If you check the R-DAS homepage (

), you will find that they sell a gps module ready for connection with the R-das. It's a ordinary gps in most ways, and on this module or board if you like, you'll also find a Atmel AVR uC. This uC does the magical things; stripping the data from the gps ( NMEA ), so that we get only what we need. It also converts the stripped binary stream to fit onto an I2C bus.

What I relly need to know, is how the NMEA data looks after it has been stripped, and in which format, or protocol if you like it sends the data. So when I use my own GPS and my own Atmel AVR, I can copy this behaviour and make the R-DAS believe that my homemade GPS-MODULE (not gps reciver), is infact the original. I also need to know what adress the R-das motherboard is, so i know where to send the data on the I2C bus, and I need to know if there are some interrupts in this picture....

At least, but not less, the answers to your 1.2.3.4.5.6.7.8. points of wisom ;)

1. I have a gps, ( Magellan Colortrack )
2. I know the NMEA protocol, at least good enough to find what I'm looking for
3. I know exactly what kind of NMEA strings my GPS sends, and I can read them with rs232
4. I need some more studying here, but I think I got enough info to understand the basics.
5. I know some ASM, and some C. ( Got educated people who can help me here )
6. In my case BASIC,...? I dont want to use BASIC, I use C and ASM. And on the reciever side I use C++.
7. I actually live in a student house, so thats kinda complicated. And if everyone with an electronics projects should learn to live without friends, than we all would be pretty asosial types.
8. No not dry martini, my favourite is a cold MACK BEER from Tromso Norway :)

Thanks for your post, and I hope that things are more clear now :) It was funny to write this so, no hard feelings :)

Regards Bernt-Johan Bergshaven

"Bernt-Johan Bergshaven" wrote

It seems the easyist way to do this is not to use the I2C bus for your data, but to hook into the serial stream being sent to the transmitter and rewite it using the values from your GPS.

RDAS --- FILTER -- TRANSMITTER | YOUR GPS

There are several posts on the R-DAS mailing list on Topica which mention this. It is a better route as the tramsmitter serial protocol has been published by AED on the above list.

Stephen.

"Stephen Woolhead" skrev i melding news:bjn_b.9114173$ snipped-for-privacy@news.easynews.com...

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Yes, i read some information regarding the serial bus between the R-DAS and the transmitter, and this may be the right way to go :) Thanks for all your help.

But still: If there are anyone out there with a RDAS and an origial gps module, it would be great if you used an I2C sniffer and collected the information sent between theese to components. So that projects in the future can be built with I2C support.

Thanks again. Regards Bernt-Johan Bergshaven

Okay... Got it!

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True... the fog is beginning to lift... I'm beginning to understand...

NOW I understand! Actually, that would be very interesting information to know!

I don't have the RDAS GPS module....

But, tell you what... I've got the RDAS with the optional magnetometer and

2-axis accelerameter board... I know it's not the GPS, but I'm sure we can glean a little information about the bus by using BreakOut or some other such tool we've got laying around the shop.

to

Understood...

wisom

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friends,

Heh, heh... great post. Not sure how much I can add to the pool of knowledge, but I could probably snap a picture of the addressing scheme. If memory serves, it's a simple 'first board', 'second board' type of thing.

Yes, very clear... thank you! BTW, I'll also query RDAS and see if they can impart a bit of wisdom.

No, no... no hard feelings at all... in fact, in re-reading your post... I'm not really sure why I didn't understand you the first time.

Best.

Mark