R/C Tech Forums - Transponder Design

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R/C Tech Forums (https://www.rctech.net/forum/)

- Radio and Electronics (https://www.rctech.net/forum/radio-electronics-137/)

- - Transponder Design (https://www.rctech.net/forum/radio-electronics/688396-transponder-design.html)

Payalneg

04-26-2014 06:38 AM

Quote:

Originally Posted by kinetisist (Post 13213212)

I would love to build my own mylaps hybrid compatible transponder ... is there a kit available?

No :rolleyes:

luluFRA

04-28-2014 05:19 AM

Quote:

Originally Posted by edeca (Post 13119546)

Do you have a schematic? I can see a custom wound balun and I assume the capacitors are for filtering, but I don't see any amplification?

What sort of signal level do you get from yours? And how do you amplify it afterward? I am simply using opamps and a comparator now to turn the signal back into a digital pulse train.

My first attempt was a custom winding on a binocular core, this worked OK but wasn't amazing:

http://i.imgur.com/4YFqzbk.jpg

The newest one works much better and uses a Mini-Circuits transformer as a balun:

http://i.imgur.com/0nOnqX0.jpg

Unfortunately with a 470R resistor in the loop the second one is targeted at a 52R impedance system (the balun is 1:9) but that doesn't matter as I'm not attempting compatibility with AMB.

Where did you buy your mini circuit transformer ?
Thanks

howardcano

07-25-2014 04:17 AM

Conversation continued here (from decoder thread):

Originally Posted by howardcano
I ran into a similar situation with my transponders. Here is the transponder thread:

Here is the particular post:

This post doesn't mention the "ghost numbers", although (if I recall correctly) the remedy described did fix this also.

Quote:

Originally Posted by condac (Post 13423419)

Great information, but i have not find any status message on my AMBrc DP, how does the status message "preamble" look like, if any? I have a 200MHz recorder but it only record just enough time to get a id message in one frame (without triggers) so i have to try many times before i randomly get a message at the same time it records. And the antenna pickup is not great so the information is bad most of the time.

The preamble is the same for "ID" and "status" messages. There are seven different "status" messages, with one sent every fourth transmission (with the "ID" message sent the other three transmissions).

condac

08-01-2014 12:35 AM

Here is my source code for a transponder using an attiny25. So you can program your own with own numbers.

https://github.com/condac/openAST

It have the known issue to send "ghost numbers" and not working with patched decoders yet.

condac

08-01-2014 02:44 AM

http://i.imgur.com/cHrqaEP.jpg
It was not impossible once you understand its not a normal Convolutional code and no trellis diagram works at all :)

All credits to OM2KW for putting a lot of work into this.

condac

08-01-2014 03:00 AM

For people wanting to read their transponders and don't have a super expensive osciloscope, you can get a "Open Bench Logic Sniffer" google it and you will find local retailer.

putting it at a distance from the transponder with a cable as antenna and you can read the transponder, i use it at 100mhz to get length enough to record one message, and you have too try a lot of times to get the recording to start at the same time the transponder sends data but it will work in the end. You have to test for a good distance to get a signal that is not to powerful or to weak.

tonybod

08-01-2014 03:04 AM

Am I right in saying that we can now build our own transponders based on Payalneg's hardware and your code?

All I can say is thank you very much for all your efforts. I'm sure there are a lot of people who appreciate what you have done.

condac

08-01-2014 03:14 AM

Quote:

Originally Posted by tonybod (Post 13438135)

Yes!

Payalneg's hardware needs some fixing, the ghost issue is probably due to bad antenna design in it. I have made a design using input for the Vcc to handle more than 5v also that is common in RC cars.
Hardware cost is about $8 at maximum and super common parts.

howardcano

08-01-2014 10:06 AM

Quote:

Originally Posted by tonybod (Post 13438135)

Aren't we forgetting someone? :cry:

tonybod

08-01-2014 10:08 AM

Quote:

Originally Posted by howardcano (Post 13438781)

Aren't we forgetting someone? :cry:

Sorry Howard, yes, thank you as well.

Candre23

08-02-2014 06:40 AM

I've been watching this thread for about a year. I think it's really great of condac to open-source his code, and I hope this will lead to more improvements and possibly ready-made transponders for folks who aren't comfortable soldering and flashing.

However, I cannot overstate how amazing howardcano's work has been. None of this would have happened without his initial work, continued efforts, and advice to others. A simple "attaboy" doesn't seem sufficient for what he's achieved, but it's all I have to offer.

luluFRA

08-02-2014 10:33 AM

Quote:

Originally Posted by condac (Post 13438061)

Here is my source code for a transponder using an attiny25. So you can program your own with own numbers.

htp s:// gith ub. com/con dac/ope nAST

It have the known issue to send "ghost numbers" and not working with patched decoders yet.

(I cant add url so fix this for me someone)

good job, file in ".sch" are eagle file ?

thanks.

condac

08-02-2014 11:24 AM

Latest commit on github now contains a C program and Java program to decode and encode.
To use the java program to encode run:

Code:

cd encoderProgram/java/dist

 java -jar rctcode.jar 3456789



      encode2: 0101001000010111011001000101010000000000

    encodeOut:  1110000111001011111111010010100100101000000100110001110100010011001111110000

        ldi  d1,  0xe1

        ldi  d2,  0xcb

        ldi  d3,  0xfd

        ldi  d4,  0x29

        ldi  d5,  0x28

        ldi  d6,  0x13

        ldi  d7,  0x1d

        ldi  d8,  0x13

        ldi  d9,  0x3f

And the last lines you can paste in the asm file when you build your program and you have it ready to go.

To decode, input a binary string as argument (at least 12 char)

Code:

java -jar rctcode.jar 1110000111001011111111010010100100101000000100110001110100010011001111110000

known decoded: 01010010000101110110010001010100000000

known decoded int: 3456789

And give credit to OM2KW for cracking the FF sequence making this possible.

condac

08-02-2014 11:25 AM

Quote:

Originally Posted by luluFRA (Post 13440680)

good job, file in ".sch" are eagle file ?

thanks.

I started a project in KiCAD for hardware design, now its just electric schematics no pcb designs

luluFRA

08-02-2014 12:47 PM

perfect job !
condac, why you don't used the howard transponder design ?

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