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Author Topic: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module  (Read 37135 times)
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I see you are in the UK, have you seen the FPVUK forum post(s) regarding 459MHz use?
It would be good to see you over there.

http://www.fpvuk.org/forum/index.php?topic=2551.new;topicseen#new

The ability to use 459MHz was partly why I started the project! I have been reading the fpvuk and openlrs forums for a while, but I don't really want to go in and be seen as competing with OpenLRS. This is just a personal project. Although it would be nice to have some local RC people help with some testing. I don't really have many friends near me that enjoys going out to do range tests!!

What are your plans for the smaller PCB?

I'd be very interested in a couple of smaller (Futaba module compatible) boards - I'm willing to assist with costs.

They are only slightly smaller. Rev1 was 50x50mm, Rev2 will be 50x43mm. Right now they don't quite fit inside my 9x radio, the new ones should just fit. They are not designed to fit into Futaba modules, and because they run at 5v you will need to modify your radio slightly to get a 5V wire out. I attached some pictures to show how ghetto my mounting method is!

I would like to keep the large DIP 28 atmega328, because it's easier to get, solder, program bootloader and because I have a lot of them! Making boards is really cheap, I don't really need any financial support for that. What I plan to do is release the gerber files, so that if anyone want some boards all they have to do is to send the files to a PCB fab. It would be really nice to have more people help with the software though.


* IMG_8373.JPG (154.66 KB, 640x480 - viewed 63 times.)

* IMG_8372.JPG (142.6 KB, 640x480 - viewed 46 times.)
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Devonian are you willing to modify the interesting features of openlrs firmware (failsafe, rssi etc.) to work on this nice hardware?

Edit: Zitron hope you received my pm with my address. Zitron hope you retain the same connections on your board so more code fluent friends on this forum can help me out with the code smiley-grin

I will reserve 3 for you and send 3 to Mauzer. So now I don't have any more to give away.

I have attached my Tx code, an Rx test code (no servo) and the code used on my HK450 heli, which is a little bit complex because it has CCPM and PID governor. You need to install the arduino RF22 library, and software servo library (I'm having some glitching problems with the default hardware servo library). Please understand that this is just my personal project, not yet a proper ready to use general purpose tx/rx, I have only implemented the things I wanted.

Right now the software only supports transmission on a single frequency (I set it at 459.5, but you can change it to whatever you want), 8 channels at ~50Hz. The Tx takes PPM.

* rf22_RC.zip (5.64 KB - downloaded 36 times.)
« Last Edit: March 21, 2012, 05:33:41 pm by zitron » Logged

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Great stuff!  It is the most simple and cheap Lrs that I have seen, just amazing.  Zitron, Did you have an additional pair of boards that could sell me? Where I live I can not get anyone to manufacture pcb's with that professional look in few quantities. I was thinking of trying to do a diy Openlrs, but now I saw this topic ... no way!
Next project: Zitron lrs cheap!  smiley

Thanks in advance,

Daniel
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Yeah I can send you the 3 rev 1 boards msev wanted. I can send him the new boards if he still wants them.


BTW I don't know if anyone would be interested in this, but I have found that the RF22 library is not compatible with timer based hardware servos. Very weird and hard to debug. It is because the interrupt driven read function takes too long, messing up servo PWM timings. I had to modify the library quite a bit, but now I have hardware servos! If anyone else have problems with the servo library I'll let you know what to change.
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Hi Zitron,

Discover the secret - where do you manufacture the PCBs?
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Yeah I can send you the 3 rev 1 boards msev wanted. I can send him the new boards if he still wants them.

Zitron, this is great!  Glad to be able to get into your project. I'll send you a pm.

Thanks smiley-wink
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Hi Zitron,

Discover the secret - where do you manufacture the PCBs?

I use iteadstudio.


edit: BTW did you manage to get it working?
« Last Edit: April 11, 2012, 11:45:04 am by zitron » Logged

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OK guys sorry I can't keep giving away boards for free. From now on I will charge a small fee (£2 per board) just to cover my costs.

Before you decide to start this project, make sure you can write code for arduino, ideally have some knowledge about SPI communincations, can solder SMD packages, and can find all the components that you need, listed in the BOM pdf attachted in a previous post. I can help, but I don't have time to answer all the questions.
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Oh also if you want to know where to get the RF22 module, have a look at the HopeRF resellers, find one near you: http://www.hoperf.com/agent.htm

I get mine from Germany.
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OK guys sorry I can't keep giving away boards for free. From now on I will charge a small fee (£2 per board) just to cover my costs.

More than fair! 

Before you decide to start this project, make sure you can write code for arduino, ideally have some knowledge about SPI communincations, can solder SMD packages, and can find all the components that you need, listed in the BOM pdf attachted in a previous post. I can help, but I don't have time to answer all the questions.

I can solder SMD and get all the components needed; I have lots of open source arduino projects done but... I don't write arduino code... if you do not mind sending me the actual code, as well as any updates, I think I'll have no problems. If you do not mind that your project is shared, I think it might bring some progress in the project through some friends. But as I said before ... I do not write code...
Zitron What do you think? It is worth I join the project? 
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Zitron sorry for the late response.. You can send/sell the pcbs that you reserved for me to other guys...
I'll probably make my own diy single layer boards and use an arduino nano..I'll make the connections per flytrons schematic so that I won't need to tinker too much with the code..I'll make the nano removable so that I could remove it from the board when uploading new sketches (since 5V would kill the rfm22b)..

I would take yours if there would be a possibility to easily port openlrs code...but its a bit too complicated for me..
Hope you continue with your nice project and post code...Hope then when you write your code for lrs you'll still have some pcbs to sell smiley-grin.
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Hi Zitron,

I'm still interested, I'll PM you over on FPVUK.

Regds,

Nigel.
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I can solder SMD and get all the components needed; I have lots of open source arduino projects done but... I don't write arduino code... if you do not mind sending me the actual code, as well as any updates, I think I'll have no problems. If you do not mind that your project is shared, I think it might bring some progress in the project through some friends. But as I said before ... I do not write code...
Zitron What do you think? It is worth I join the project? 

You/anyone can use my design files and code for whatever purpose. Just make sure you know what you are getting into, it's not a fully featured product, and will likely to have many problems.

Zitron sorry for the late response.. You can send/sell the pcbs that you reserved for me to other guys...
I'll probably make my own diy single layer boards and use an arduino nano..I'll make the connections per flytrons schematic so that I won't need to tinker too much with the code..I'll make the nano removable so that I could remove it from the board when uploading new sketches (since 5V would kill the rfm22b)..

I would take yours if there would be a possibility to easily port openlrs code...but its a bit too complicated for me..
Hope you continue with your nice project and post code...Hope then when you write your code for lrs you'll still have some pcbs to sell smiley-grin.

I think that is probably the best thing for you to do. Trying to port someone else's code will be very time consuming, especially if you have limited experience! Also bear in mind that by the time you bought your nano, all the components and boards I think you might as well buy direct from Flytron! It would be really nice if they released a DIY OLRS kit.
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Here are some pictures of the new Rev 2 board. It's 50x43mm compared to 50x50 Rev 1.

If you are building one I suggest soldering the SMD components first, and use a bigger cap in C7 (I said 100uF in BOM, probably should be 470uF) especially if you use a lot of servos.


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Looks great Zitron, a piece of art!

Using those cheap chinese nano clones, i think i can get bellow the price of one Melih's receiver and I also save for a ftdi, since they have an onboard ftdi (I would remove the nano from the headers when uploading)..

I'd be interested in buying a booster pcb from you (same layout as Melih for the same chip), maybe if you could design it in a way that the resistors, caps, diodes,  etc would be of a bigger size, for easier diy work...Do you manufacture these pcbs by yourself?
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