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Old Jun 16, 2012, 08:47 AM
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Dennis Frie's Avatar
Denmark, Capital Region of Denmark, Naerum
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Originally Posted by jalves View Post
I read somewhere that the maximum baudrate using video closed captions is 480bps.

I thought we could use more than this (roughly 60bytes/s) to carry our telemetry, what are your thoughts about this?
I don't really have any idea - it depends a lot on how you plan to read it again. In theory you should be able to use max SPI speed, but that might be a bit tricky to read again

I would probably just test it and find the maximum speed that gives good results
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Old Jun 17, 2012, 05:38 AM
throw new IOPilotException();
IceWind's Avatar
Ireland, County Dublin, Dublin
Joined Feb 2005
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Originally Posted by Dennis Frie View Post
It's pretty easy to insert the information in the OSD, but it's gonna be a little tricky, to read it again.
If you use the empty/extra lines, it should be all black. So you should be able to generate white pixels and only have black and white = on or off. Using a simple analog circuit, you might be able to translate it directly to a digital signal again. Just an idea for an easy implementation to test the actual performance.
With the right AC-coupling i believe you will be able to detect the bits with voltage > 0 volt = 1, and voltages < 0 volt = 0. That can be translated directly to logic levels with a simple comparator.

But it's probably easier said than done

Another solution is a quick ADC - unfortunately the ADC's in Atmega is not very fast. But you might be able to use it with a few bits.
The Lynx Ground Station has it that way and is very simple.

http://www.rcgroups.com/forums/showp...42&postcount=1

I got myself a LM393 to try and make my own decoder of VBI data from a OSD I have but I haven't even touched. it.

Swap the PIC and remove the LM1881 in the circuit above and you have almost no parts as well as with the OSD.
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Old Jun 19, 2012, 06:03 AM
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Wellington, New Zealand
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I haven't managed to get back to this in the last couple of weeks but I have made some notes here.

The Arduino should be fast enough to use the same data/decoding rather than the PIC I've used. If I get stuck with data capture, I can put a different PIC in the same board that clocks at about 64MHz. But I thinkit will be OK.

I tried some standard op-amps and comparators to detect the data but they were not fast enough. The TLV3501 came from Element-14, was reasonably priced for two chips, in stock and available cheaper elsewhere if I buy more.

Paul
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Old Jun 19, 2012, 07:24 PM
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which gps can i use ? does this one work ? http://www.hobbyking.com/hobbyking/s...S_Module_.html any idea ?

do you have wiring scematics of this build ?
is it possible to use a cheap 9g servo instead of the 360 one since i have several of these here and i dont want to buy any additional stuff ?
which power do i need on the tx module ? can i use the 12v from my lipo or is it better to use 5v from my receiver ?
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Old Jun 20, 2012, 01:55 AM
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The gps seems to be the MTK little one (very good by the way), if so it is good.
Check to see if it has the Rx wire attached to allow you to program it.

Check the Wiki of this project for the HowTo.
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Old Jun 20, 2012, 07:31 AM
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the rx wire on the gps ? programming the gps ?

can anyone please do a wire scematic , the wiki really doesnt make it that clear for me ( and for others as well maybe)

one more question : can i put the gps on top of my video tx , about 3" away from my antenna ? then i could build a small module which i can swap between planes
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Old Jun 20, 2012, 08:08 AM
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Do you use a osd in your model plane?

If so, you just need to solder two wires to the gps wire (GND and Tx) doing an Y and connect the two new wires to the arduino (GND and pin 0/Rx).

If I have the time I will update the wiki with a new wire schematic for you folks with doubts.
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Old Jun 20, 2012, 10:31 AM
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i use an osd but it has just voltage and time ( 10$ HK osd ) so i need to use a seperate osd

i once ordered the big HK osd with gps but the guy who the ordered it from HK just bought the gps ^^
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Old Jun 20, 2012, 04:13 PM
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Quote:
Originally Posted by M4d_D View Post
i use an osd but it has just voltage and time ( 10$ HK osd ) so i need to use a seperate osd
An osd is not required.

You just need to solder two wires from the gps (GND and Tx) to the arduino (GND and pin 0/Rx).

I had trouble at first but if you study the wiki connections for a few minutes it's all there.
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Old Jun 21, 2012, 11:10 AM
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so it should look line this ?
what about the capacitor from the wiki ? gone ?
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Old Jun 21, 2012, 11:52 AM
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Originally Posted by M4d_D View Post
what about the capacitor from the wiki ? gone ?
Yes, gone.

I Change the audio output, the 1st pic arrangement work well, but I decide to change and use a voltage divider to adapt the audio level to my Tx audio input.

If you are using Video Tx with airwave module I recommend the last schematic (your pic) if not, the former could be better (I read somewhere that the chinese cheap Video Tx could work with audio voltages as high as 8Vpp, in this case the 1st schematic could be better) you have to try with your hardware to see which is better.

If memory serves me well you could power the gps unit from Vcc pin of the Arduino board (5V regulated) if you don't have a gps board to power the gps module.

the Raw pin could be powered from your lipo (maximum voltage 12V but I connect mine to a charged 3S lipo without problems so far).
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Old Jun 21, 2012, 12:14 PM
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i think i read somewhere that my gps need 3.3V so i am not really sure if i really want to connect it to 5v ^^
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Old Jun 21, 2012, 12:33 PM
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Then use two (reduce to one if the gps don't work with two) DIODES (1N4001 or similar) with 0,7V forward voltage drop (5V-0,7-0,7=3.6V).

I have a small locosys working this way for several years.
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Old Jun 21, 2012, 01:47 PM
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that would work but cant the arduino give out 3.3v as well , i mean there are enough digital and analog pins left
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Old Jun 21, 2012, 01:57 PM
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Can't guide you, you have to solver this or wait that someone that is reading this chime in and help.
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