simple homebuild sensor for jeti duplex

[maikoflyer]

Because of an urgent need i have done an easy to build sensor for the jeti duplex system. It can measure voltage of battery and measures also an absolute pressure sensor. The full module should be placed later inside of the r6 housing together with a voltage regulator. But only after shrinking in size. :D

The first video shows the whole thing wired and the second one wireless.

wired:
http://video.google.de/videoplay?docid=5181608075447183224&ei=hnuaSZL3DImQ2wK01PGUDg&q=jeti+duplex&hl=de
wireless:
http://video.google.de/videoplay?docid=1869727009965084876&ei=hnuaSZL3DImQ2wK01PGUDg&q=jeti+duplex&hl=de

greetings

Sorry, first video links seems not to work

[gedaso]

Beautiful ! Did you reverse-engineer the protocol yourself, or did you get some information from Jeti ? Care to share ;)

[maikoflyer]

Hi, i had to do it complete by myself. Jeti said that they will not give away any information what i can understand because they are not very big but very enthusiastic. So i have also decided to give no more information than that it works relatively easy with a dozen lines of bascom code and an atmega8.
I would destroy the full joy for you to investigate it by yourself. So, sorry, you can have a look in a german thread where you can find all necessary informations to start with.
http://www.rclineforum.de/forum/thread.php?threadid=226786&sid=3992aea0eb507a7d83f54aa94d43181b

greetings

[docmarius]

@maikoflyer: tnx for the link! You woke some instincts in me.

[maikoflyer]

I hope, the good ones. :D

[mieczotronix]

by following poitners on the German forum, I also managed to build a DIY sensor myself. The protocol is relatively easy to grasp, I can confirm.

My sensor is an interface to the Z-log allowing me to transmit altitude readings while I fly over the Duplex telemetry link.

Here's a screenshot
http://mieczu.webd.pl/modele/elektr/zlog+duplex.jpg

The circuit is only attiny2313 with 100n cap and a single resitor. So its dead easy to build. I can post a .hex file if anyone cares to build one...

[maikoflyer]

Cool!
Good work.

You are working with the internal oscillator? How fast is the z-log?

lg

Ok, have seen in the german forum that you are working with internal 8MHz oszcillator using hardware uart.
Next step would be message parsing and real variometric function. :D

[mieczotronix]

in my z-log usart rate is configurable from menu. I've chosen 38400 bps. I talk to z-log over software usart once in a startup sequence. Then I receive two 38kbps bytes ten times per second.
Yes, I'm on internal oscillator, and I guess it is going to work (at least it has been working so far) but ultimately may suffer from temperature extremities. I could do some sort of calibration, if I had a reference I could calibrate to...

[maikoflyer]

Ok, calibration is normally made with a reference frequency like quarz oscillator or a calibration byte send over serial connection. There is a reference on the atmel homepage about calibration using LIN interface and also using the same technique over simpel serial connections.
I think a cheap simple ceramic oscillator will do it with less temperature and voltage dependencies.

Do you have got the "mystery" key thingy or do you need help there?

LG

[mieczotronix]

If I have to add any quarz osc, I'd add the 8MHz across XTAL pins. I could probably calibrate to the PPM signal from Z-logs trig input. But again, this is not a good reference. There's also nobody to send me the calibration byte. Jeti BOX sits there and listens until I start sending something. Maybe there are some pulses on the Jeti-sensor <-> Jeti R8 line I could tune to, but I haven't looked at it and so far eeprom+OSCCAL way seems to suffice.
Anyway, that's only a test. I'm going to build a more advanced on-board-computer, with larger uC on crystal.

As for keys, I've managed to read codes ok, but haven't used them so far. But I think I'm on good track here. Thanks, anyway!

Tell me what's this LIN interface - there isn't such thing on 2313 I guess...

[Alan Hopper]

Hi, can you tell me if the jeti system hardware works along the same lines as the xps system http://www.xtremepowersystems.net/devinfo.php
this has a diode between the uart tx and rx pins so the tx can only pull the single wire low and a pullup at the master device. I am interested as I'm about to make some sensors for my diy 2.4ghz system, it would be great if the hardware could be compatible between these systems (obvously different firmware ).
Alan

[mieczotronix]

data format and rate is different (see the German thread for details), but I guess the wiring could be left as is. I haven't used a diode I just switch usart receiver and transmitter on and off in a sequence.

BTW has anyone worked out JEti Duplex alert codes?

[maikoflyer]

If I have to add any quarz osc, I'd add the 8MHz across XTAL pins. I could probably calibrate to the PPM signal from Z-logs trig input. But again, this is not a good reference. There's also nobody to send me the calibration byte. Jeti BOX sits there and listens until I start sending something. Maybe there are some pulses on the Jeti-sensor <-> Jeti R8 line I could tune to, but I haven't looked at it and so far eeprom+OSCCAL way seems to suffice.
Anyway, that's only a test. I'm going to build a more advanced on-board-computer, with larger uC on crystal.

As for keys, I've managed to read codes ok, but haven't used them so far. But I think I'm on good track here. Thanks, anyway!

Tell me what's this LIN interface - there isn't such thing on 2313 I guess...

For calibration, look here: http://www.atmel.com/dyn/products/app_notes.asp?family_id=607 and search for "calibration".
This http://www.atmel.com/dyn/resources/prod_documents/doc7653.pdf describes runtime calibration with serial port over LIN Interface techniques.
If you like to read more about LIN search for "LIN".
http://www.atmel.com/dyn/resources/prod_documents/doc1637.pdf
http://www.atmel.com/dyn/resources/prod_documents/doc7548.pdf
...

You don't need to use LIN. It is more that they are using a send byte for calibration. That's all it is about. :)

LG

[mieczotronix]

Thanks, I know these docs, although I didn't know anything about LIN, but...
I'll be building a brand new sensor or rather should I call it a board computer (with altimeter, gps, voltage, current metering + camera pan/tilt control) and I will simply solder a crystal to the beast.

[JimDrew]

Hi, can you tell me if the jeti system hardware works along the same lines as the xps system http://www.xtremepowersystems.net/devinfo.php
this has a diode between the uart tx and rx pins so the tx can only pull the single wire low and a pullup at the master device. I am interested as I'm about to make some sensors for my diy 2.4ghz system, it would be great if the hardware could be compatible between these systems (obvously different firmware ).
Alan

Alan,

The JETI sensors act basically as a remote control for the JETI box. You could easily make our sensor firmware so it is compatible with both XPS and JETI systems. However, be aware that 9600 baud is extremely slow so you would need to make sure that you account for that while coding your sensor reading routine.

Our data rate is 125,000 baud and our data packets are typically 6 bytes. JETI uses 9600 baud with data packets being 34 bytes because they update the entire display (spaces, etc.) not just valid data. So, the max refresh with JETI is very slow by comparison.

Using the diode is the proper way to make sure that any simultaneous bi-directional communications do not destroy the serial port on the CPU, and to also protect it from a direct short to ground or +V.

[mieczotronix]

Now I've been building my DIY jeti box. I'm hoping it will read data in an extended format sent from my diy sensor (onboard computer: altimeter/gps/current/mah/voltages), format and pack data from various jeti sub-pages onto big 4x20 LCD. It will also have a SP03 speech synth module to speak out altitude/distance/warnings (as I've found standard audible feedback of jeti duplex (morse code - letters only) a little bit awkward). It will also have a dial and some more buttons to ease-up its operation while flying a plane.

http://www.mieczu.webd.pl/modele/elektr/DIYjetibox.jpg

[mattijs321]

nice work!!!

Now the obvious question...can anybody give a brief explanation about the protokol in english??? :)

[mieczotronix]

I used Babelfish to translate the German thread to English. I read the translation twice and it was enough to grasp the basics. Anyway tech spec details are quite 'international'. The guys on the German forum helped me a with my hacking, and I appreciate that. For a reason they did not want the protocol to be publicly documented more than it was. So I guess the only way is go and try to figure it out by yourself and ask them when in doubt (you can also PM me after you dig into it and get stuck).

[ulrich/Germany]

Our data rate is 125,000 baud and our data packets are typically 6 bytes. JETI uses 9600 baud with data packets being 34 bytes because they update the entire display (spaces, etc.) not just valid data. So, the max refresh with JETI is very slow by comparison.



Thats a funny way to promote the XPS System where you can not use any sensors right now.
It has a higher data rate but 125,000 baud multiplied with zero is definitively lower than 9600 baud.

Great work what you did, we will see what future and Jeti will bring to us.

[mieczotronix]

I've just made a smd pcb for zlog<-> jeti duplex interface. It has attiny 2313 on board

This is the bare PCB
http://mieczu.webd.pl/modele/elektr/zdl1.jpg

and here it is connected to Z-log
http://mieczu.webd.pl/modele/elektr/zdl2.jpg

this bunch of colorful cables is soldered temporarily for ISP programming, after I finish the software it will be removed.


he parts list is:
1 x attiny2313 in SOIC
1 x SMD crystall 16 MHZ

2 x 22pf (for crystal resonator) - C1,C2
1 x 100nf (decoupling cap) - C3
1 x 100R
1 x 10K
1 x 150R - 350R (series with LED)
1 x 0R bridge (R4)
1 x LED
all R,C,D parts are 1206

1 x 3pin angled pin header (for connecting Jeti)
1 x 4pin straight pin header (for connecting to zLog socker)
3 x female rc cable terminals (for connecting to ZLog pins)

PCB 4 x 2 cm

I'll need to improve the code yet, I will put .hex here in a while

[sigurd]

Alan,

The JETI sensors act basically as a remote control for the JETI box. You could easily make our sensor firmware so it is compatible with both XPS and JETI systems. However, be aware that 9600 baud is extremely slow so you would need to make sure that you account for that while coding your sensor reading routine.

Our data rate is 125,000 baud and our data packets are typically 6 bytes. JETI uses 9600 baud with data packets being 34 bytes because they update the entire display (spaces, etc.) not just valid data. So, the max refresh with JETI is very slow by comparison.

Using the diode is the proper way to make sure that any simultaneous bi-directional communications do not destroy the serial port on the CPU, and to also protect it from a direct short to ground or +V.

I'm trying to work out an autopilot acting from telemetry data and controlling the aircraft via the Tx. What you said, does it mean there will be more latency/delay in the system with the jeti? is it a lot?
What the other fellow said, that you cannot connect sensors to the XPS, does it mean it's not possible, or just that there are no sensors on the market for it yet?


mieczo - does the zlog interface work yet?

[mieczotronix]

Yes it basically works. Although I am not sure whether it displays the right climb/descent rate. Haven't got time to test it in flight yet. On my bench it seems to work.

[JimDrew]

We provide complete schematics, PCB layout, and source code for a dual (temperature/RPM) sensor. Some people have adapted this to other CPU types and languages, and others have expanded upon the example and made quad sensors.

[sigurd]

ok jim, that is cool, ive looked a bit at your pages and tried to install the xdp software on my vista just to see what it is about. None of the programs installed correctly, but this is a bogged down sketchy pc.

How about adding some D/A outputs to the telemetry station. That way one could put analog gauges and stuff and read important values from the sensors without using the pc.

miecso, congrats, very cool! Is there a particular reason you did not use the jeti mvario sensor instead?

[JimDrew]

You must have the hardware in order to use the software. We will be releasing a windows API to get access to the telemetry data directly.