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Old Dec 02, 2008, 06:54 AM
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Home made RC transmitter 2.4Ghz

Hello,
You may be interested to build you own RC transmitter and receiver as I did.
It is based on Arduino board (and derivatives) and Xbee, it is easy to build.

For the transmitter box, I reused an old radio with it sticks, and all the electronic has been replaced. The receiver is made with a Wee+Xbee.

You will find more informations on my blog:
First tests:
http://effetdebord.blogspot.com/2008...ype-first.html

First fly:
http://effetdebord.blogspot.com/2008...emier-vol.html

And the rest of my blog:
http://effetdebord.blogspot.com

It's a great fun to fly with your own radio
Olivier
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Old Dec 02, 2008, 07:53 AM
"MAYONNAISE"
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Le Treport, France
Joined Jun 2004
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Bonjour Olivier,

Beau projet, avec du beau linge ...

dommage que, pour les 2 premières lignes ... :

Quote:

Le blog que vous recherchez est introuvable
Alain
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Old Dec 02, 2008, 08:14 AM
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Quote:
Originally Posted by Acetronics
Bonjour Olivier,
dommage que, pour les 2 premières lignes ... :
Alain
Merci, c'est resolu.
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Old Dec 02, 2008, 10:35 AM
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hi Olivier,
nice work.

i'm currently working on a similar but with AVR ATmega2561 connected to UGWJ4USHN33 modules.

the UGWJ4USHN33 is based on the Cypress CYRF6936 chip and was quite time consuming to get working.
my system is ready for testing but unfortunately i have been traveling with work a lot recently and have not yet managed a test flight.

i did not use the Xbee modules because is did not like the restrictions of it's packet structure.
did you manage to find a way to get the Xbee to send data directly or are you limited to transmitting when it's buffer is full?

so the beauty of building a RC system this way is it is easy to get data back from the plane. i can currently monitor on board battery voltage and have plans to implement current draw and air pressure (for airspeed and altitude measurements).

it is also easy to save mixer and trim settings on the aircraft rather than having to have multiple configurations on a transmitter.

so anyway, i'll be documenting my work eventually but i'm afraid i have not used my french in 10 years so won't be much use on your open source project.


dunk.
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Old Dec 02, 2008, 12:43 PM
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Thanks.
Nice to hear from people who have worked on similar project.

Your use of ATmega2561 it is interesting. I am now getting outof space on the Arduino (16kb flash only) so I may take bigger. I have an Atmega 644p (256kb) that I could use, and better an AVR 32bits.

About the Xbee, I used it mainly because of its simplicity. My goal was to make the "coder" part, more than the transmit part. Xbee can work in both direction, but currently I use only transmit.

For the management of the buffer, well obviously the buffer full situation should be rare, otherwise there is too much noise on the channel. I do not really handle this situation, and if it occurs, current packet are simply discarded. But so far when flying, I have not seen any delay.

On my blog, there is also a reference to an opensource project which is not the same thing than my Arduino project. This rcopensource project has recently started, but if you are interested, you are welcome. Most of the people on that list should understand/write English.
cheers,
Olivier
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Old Dec 03, 2008, 06:01 AM
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yea, i chose the ATmega2561 because it has 2 16 bit timers attached to 3 I/O pins each so i can control 6 servos in hardware without having to worry about servo timing loops.
it has lots of program space too.
i'd recommend it if you have the ability to use surface mount components.

i have not used any of the 32bit AVR range.
is the programing environment the same?
i'm guessing the main advantage is faster execution of code using a lot of maths?


dunk
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Old Dec 03, 2008, 06:26 AM
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May be I misunderstood. I thought you were using the ATmega2561 for the tramsission part, not the receiver.
In my project, the transmission is numeric, so I transmit the pulse value as numeric value (2 bytes hexa) through the Xbee.
On the receiver side, I used the Atmega168 with two timers, and handle the timings to servos with software. Currently it support 8 servos, but reasonably could go up to 10.

For the avr32, I have not yet tried it. There is an avr32-gcc version available, but it needs to be compiled and looks not so easy to install than the 8 bits avr-gcc. For mathematic, it should be better, but it's true that with the current 10bits ADC, 16 bits would be enough.
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Old Dec 03, 2008, 06:50 AM
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Quote:
May be I misunderstood. I thought you were using the ATmega2561 for the tramsission part, not the receiver.
yup. i'm using the ATmega2561 at both ends.
as i'm transmitting in both directions i'm trying to keep the platform as similar as possible at both ends so i can keep much of the code the same on the plane and on the ground.

Quote:
On the receiver side, I used the Atmega168 with two timers, and handle the timings to servos with software. Currently it support 8 servos, but reasonably could go up to 10.
i like to control servo pulses in hardware if possible as it greatly simplifies timing if you want to use interrupts in your code.
it does mean you need to chose an AVR with the right timers though.
it's a personal preference thing i guess.
if i ever need more than 6 servos then i'll have to resort to software control of servos or change AVRs.


dunk.
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Old Dec 03, 2008, 11:45 AM
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Hi,

I'm also working on almost the same concept, a fully 2.4Ghz digital chain.
Currently using TX module from LP5DSM (I'm waiting my unigen module) and homemade transmitter (PIC24H based + phone LCD).
It should be fully compatible with DSM2 devices, especially the (low cost) remote receiver SPM9545 (the best receiver for my project, I cannot make such PCB myself), it will drive modified servos (and DIY ESC later) via an i2c bus (ya, I don't like PPM).
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Old Dec 03, 2008, 12:44 PM
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Hi Angelion,
This is interesting.
How do you make the compatibility with DSM2 devices ?
Do you know the protocol they use ?
And for the servo control, have you considered also CAN ?
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Old Dec 03, 2008, 12:49 PM
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Good Morning Olivier

Have you thought about using the ATMega328? I thas double the memory of the ATMega128.

I too am working on a similar project and will watch this thread for updates.

I am sorry I do not read French so your site reference is not good for me, but the photos were great.

Jim
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Old Dec 03, 2008, 12:53 PM
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Hey Jimnaz,
My blog is written in english for most parts... so you can read it.
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Old Dec 03, 2008, 02:03 PM
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Je n'avais même pas vu que c'était en Francais, honte sur moi
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Old Dec 04, 2008, 03:16 AM
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So many french people doing 2.4 GHZ stuffs, got a project myself. I decided not using any 2.4 GHZ existing module. I've just finished routing it. I'am using a CC2520 + CC2591 front end for the 100 mW boost. It seems to be tricky to obtain any good result in term of band occupation but I want to try because of the low price in the end.
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Old Dec 04, 2008, 04:18 AM
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(Ooops, I missed your post yesterday)


Quote:
Originally Posted by obor
This is interesting.
How do you make the compatibility with DSM2 devices ?
Do you know the protocol they use ?
Thanks to my SPI spy, CYRF6936 IC is used in the DSM2 compatible LP5DSM TX (and spektrum remote receiver?), it's the same IC in unigen module (+power amp), further informations soon.

Quote:
Originally Posted by obor
And for the servo control, have you considered also CAN ?
Too complex for this purpose, and I want a really tiny µC for the receiver.
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