Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module

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.

Hi Zitron,

Discover the secret - where do you manufacture the PCBs?

zitron:
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 :wink:

Mauzer:
Hi Zitron,

Discover the secret - where do you manufacture the PCBs?

I use iteadstudio.

edit: BTW did you manage to get it working?

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.

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.

zitron:
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!

zitron:
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?

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 :D.

Hi Zitron,

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

Regds,

Nigel.

Dfidalgo:
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.

msev:
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 :D.

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.

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.

IMG_8394.JPG

IMG_8396.JPG

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?

zitron:
edit: BTW did you manage to get it working?

Not yet. Waiting for RFM22 boards...

These boards looks great!

zitron:
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.

Can you upload your modifyed library or explain here what to change? Did you solved the glitches issue with this mod?

Regards

msev:
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?

Yeah except I really don't know much about RF design... If I tried to make one of those high power amps it would probably catch fire!

Dfidalgo:
Can you upload your modifyed library or explain here what to change? Did you solved the glitches issue with this mod?

Well I fixed the glitch problem awhile ago by using software servos, now hardware servos are also working, which is more processor efficient.

I will try to release a simple "reference" code sometime next week, it will include all the libraries, and will be a simple PPM->Tx->UHF->Rx->Servos thing.

Edit: Important notice, please make sure that you can find a 5V source on your radio, this board does not have a voltage regulator for the arduino, so you can not power it direct from your TX battery.

zitron:

Dfidalgo:
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Edit: Important notice, please make sure that you can find a 5V source on your radio, this board does not have a voltage regulator for the arduino, so you can not power it direct from your TX battery.

Well, my TX is a Graupner MC-19, I think that a LM7805 can solve the problem dont? Anyway, I do intent to use your tx uhf with a joystick that generates the ppm signal from another arduino (details here: http://www.ianjohnston.com/content/index.php?option=com_content&view=article&id=30:project-rc-ppm-trainer-port-joystick) I have done this on my homemade console that you can see here at work:
Homemade radio console for FPV - YouTube

The joystick will be a old but cool "Top Gun" , and a pair of old T2m rudder pedals, all for FPV obviously.

zitron:
Yeah except I really don't know much about RF design... If I tried to make one of those high power amps it would probably catch fire!

Don't worry man, i have a uncle that is firefighter ... :smiley: If you make one RF booster, I'll test for you! XD

zitron:
Yeah except I really don't know much about RF design... If I tried to make one of those high power amps it would probably catch fire!

No need to worry about that since at would be runing it at 1/7 of its total output power and in such conditions you dont even need a heatsink for the chip..

Dfidalgo:
The joystick will be a old but cool "Top Gun" , and a pair of old T2m rudder pedals, all for FPV obviously.

Wow that is pretty cool, and yes LM7805 will work fine, that's what I use. The board draws very little power.

Also I thought I should update the schematics and bill of materials, there are some slight changes. See attached.

BOM_Rev2.pdf (31.5 KB)

Schematics V3.3.pdf (74.6 KB)