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

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)

msev:
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..

One step at a time, let me get this simple board working properly first!

zitron:
One step at a time, let me get this simple board working properly first!

You are right! It will take me a lot of time till I'm at the stage to start building olrs....since I intend to first try and play with a diy 2.4ghz booster based on rf2126 chip...

In the meantime I'd like to ask you, which vreg could be a suitable replacement for the one Melih uses - mic5205...I read the datasheet and saw it has a really low dropout voltage or something like that..Is there any other which has a low dropout voltage but a higher maximum current?

So you use LM1117?

Regarding Melihs design besides powering the atmega and rfm22, does anything else use power (maybe the driving of the servos? and if so do they use such a small amount)? Because that mic5205 has a small max current..
Thanks!

msev:
In the meantime I'd like to ask you, which vreg could be a suitable replacement for the one Melih uses - mic5205...I read the datasheet and saw it has a really low dropout voltage or something like that..Is there any other which has a low dropout voltage but a higher maximum current?

So you use LM1117?

Regarding Melihs design besides powering the atmega and rfm22, does anything else use power (maybe the driving of the servos? and if so do they use such a small amount)? Because that mic5205 has a small max current..
Thanks!

The RF22 only draws 85mA at full power, plus maybe 20mA for the atmega. Also the transmission only happens in quick bursts so it's not always on. The mic5205 should be plenty, since servos are powered separately from the BEC. I think any regulator will work as long as the drop out voltage is not much more than 1V, obviously lower is better to prevent brownouts.

zitron:
The RF22 only draws 85mA at full power, plus maybe 20mA for the atmega. Also the transmission only happens in quick bursts so it's not always on. The mic5205 should be plenty, since servos are powered separately from the BEC. I think any regulator will work as long as the drop out voltage is not much more than 1V, obviously lower is better to prevent brownouts.

Thanks! you gave a very clear answer :D...Why does flytrons TX module have 2 vregs, mic5205 and a LM2937?

What you think about a integration of the RFM12BP with your circuit in the future? Seems to be very similar to rfm22 but with 500mw. It is possible without modifications on your code?

Regards

msev:
Thanks! you gave a very clear answer :D...Why does flytrons TX module have 2 vregs, mic5205 and a LM2937?

They use 2 at the same time?? I really donno, will have to look at their schematics...

Dfidalgo:
What you think about a integration of the RFM12BP with your circuit in the future? Seems to be very similar to rfm22 but with 500mw. It is possible without modifications on your code?

No the RFM12BP (and lower power RFM12) uses a completely different RF chip. Although there are probably arduino code for it somewhere on the intarwebs since it's been around for a while.

Yep two vregs, one normal and one ldo...Is it because of the buzzer, since thats the only additional element added.

zitron:
No the RFM12BP (and lower power RFM12) uses a completely different RF chip. Although there are probably arduino code for it somewhere on the intarwebs since it's been around for a while.

Ok, will be easier to maintain rfm22 and when everything is operational, use the rf2126 booster mentioned by msev (datasheet says it is compatible with 433MHz).

What would I have to modify in the circuit to use it for 433MHz? In regards to that example circuit for 2.4GHz?

Take a look in the attached file.

RF2126_datasheet.pdf (181 KB)

Thanks, I must have had a "shortened" version of the datasheet... That looks great..hope these chips will still be available once I get to the stage of building a booster...Dfidalgo if you build it be sure to post some pics of it, a tell where you got the chip :slight_smile:

Today I received the Zitron PCB's, look much better in my hands than here in the pictures ! :smiley:
Now just need to buy the RFM22.

Thanks Zitron :wink:

My PCB's are in the post as well :slight_smile:

I ordered my HopeRF modules here

Nigel.

What differences are between RFM22-S1 and RFM22-S2? Only the crystal size?

Mauzer:
What differences are between RFM22-S1 and RFM22-S2? Only the crystal size?

Yes, as far as I am aware, plus €0.50 better price !!

Nigel.

Dfidalgo:
Today I received the Zitron PCB's, look much better in my hands than here in the pictures ! :smiley:
Now just need to buy the RFM22.

Cool! Let me know how it goes!

Mauzer:
What differences are between RFM22-S1 and RFM22-S2? Only the crystal size?

I heard someone mention that the bigger crystals have better frequency tolerances, but that could be just a rumour.

Hi guys,

For those of you building the board, here's a test code to make sure that the ATMEGA is working. It simply blinks the red and green LEDs:

#define OUTA 18
#define OUTB 19

unsigned int duration = 500;

void setup()
{
  pinMode(OUTA, OUTPUT);
  pinMode(OUTB, OUTPUT);
}

void loop()
{
    digitalWrite(OUTA,HIGH);
    digitalWrite(OUTB,LOW);
    delay(duration);
    digitalWrite(OUTB,HIGH);
    digitalWrite(OUTA,LOW);
    delay(duration);
}

I got my parts together now for a build of Zitrons latest board.

Works fine with the 'blink' test program.

When trying to compile the specan.pde - I get lots of errors due to missing files...
FastSerial.h
RF22.h
C++.h
Menu.h -- and many more.

@ Zitron,
I guess you use other library files when making your specan & Tx/Rx firmwares.

Is there some single download I can get the required lib files or do I need to hunt them down individually?

EDIT
Tracked down a bunch of missing lib files and now the only remaining compile error is:

C:\Arduino\arduino-0023\libraries\RF22\RF22_Specan.cpp:379: error: prototype for 'boolean RF22::setFrequency(float)' does not match any in class 'RF22'
C:\Arduino\arduino-0023\libraries\RF22/RF22.h:813: error: candidate is: boolean RF22::setFrequency(float, float)

What do I need to change/add??

/EDIT

So close and yet so far !!

Nigel.

Hi Great Find this Good work !!!!!!!

I downloaded the programs and Pde. but i get compilation errors almost so much that it looks like im missing a library , can some one please confirm this ? i have played with the RF22 modules alot so i have the RF22.h libraries but i cant get this source code to compile

any help would be great