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1  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: February 08, 2013, 03:04:22 pm
Oh yeah EEPE I remember that now!

That's a shame about the quality issues. Did they really use a Atmega88? Damn my OSD code is 14k with arduino bootloader... Maybe able to squeeze out some stuff like the artificial horizon and make it below 8k... It's almost worth replacing the MCU with a atmega168.

Oh BTW I forgot to say that video I posted was done by recording just the OSD output while replaying logged data and overlaying it on the key chain camera video in the video editor.

I did think about diversity, but I don't know anything about RF to design a RF stage with switches. I was thinking about having 2 RFM22 modules on one PCB, which could also allow you to transmit and receive at the same time.
2  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: February 08, 2013, 11:30:59 am
I think I have er9x. Flashing the firmware was the first thing I did when I got the radio, can't remember the option to save model memory. If er9x is compatible I will definitely give it a try.

My FPV Tx is 500mW, not that powerful, but much more than the 47mW or whatever the wifi router puts out! My next goal is to set up my tri for FPV, they look like so much fun to fly!

I'm pretty sure the HK Mini OSD is arduino and MAX7456 based: https://www.youtube.com/watch?v=hMUvrjivOQM. It's only $24.99 INCLUDING the GPS! That is ridiculously cheap. When I made my OSD they cost ~$100 without GPS. I wouldn't bother making my own these days.

Also did you see the HK 433MHz Open LRS thing? I guess Melih is not happy. I wish they copied my design so I can just buy it from HK instead of getting all the parts and building it myself  smiley-grin. It's fun soldering the first couple, now it's just annoying.
3  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: February 07, 2013, 07:20:57 am
That is sweet! I will have to check it out. Do you lose your model settings if you flash different firmware to the 9x? I hope not.

I haven't done much because of the crappy weather and I have too many projects going on. Flew my tri for a bit, it's not properly tuned, but is still very nice. I am terrified of my HK450, but I can hover the tri around the kitchen. I will definitely setup FPV on it eventually. There's no way I will fly the 450 FPV. I have a 2.4GHz FPV system, but every time I turn it on to test it my house mates (probably neighbours too!)  lose wifi. Maybe I will get a 5.8 system. If you are thinking about DIY OSD, I have made my own ages ago, before kg4wsv made his MAX7456 lib (check out this very old and long thread http://arduino.cc/forum/index.php/topic,8785.0.html). You can probably use the same code in any of the arduino-MAX7456 OSDs sold everywhere.

I finally got around to edit the video of my autopilot test crash last year, you can see my OSD in action although replaying logged data: https://vimeo.com/58801611

4  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: January 18, 2013, 10:03:04 am
Cool, I just test flew my multiwii tricopter last weekend, it's pretty awesome! I didn't bother with the PPM, too lazy. I think I will add a battery voltage warning to the telemetry when I have time.
5  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: December 01, 2012, 07:17:24 am
I couldn't tell from your video, but make sure you also check the hardware power selector/switch next to the RF22. You shouldn't need to change the software if you just add a jumper.

For power I just soldered a wire from the 5V reg on my 9X.
6  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: November 29, 2012, 04:48:55 pm
Nice! Were you flying on 1mW? 1mW Should be good for 100m with normal antennas.
7  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: November 24, 2012, 12:53:41 pm
Wow awesome! I like the changes.

Which version of the 9x firmware do I need?

I'm thinking about building a tricopter, I might just copy your setup!
8  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: November 21, 2012, 05:54:51 pm
Code:
Here it is: http://code.google.com/p/zlrs/

Sorry I don't know how to use google code, where is your code?

Hello zitron.  Can you summarize what modifications you have made to your RF22 lib?  What problems did you need to fix?

I am really bad at documenting stuff, I think I basically moved the read data stuff from the interrupt handler to only run when you call the receive function.
9  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: November 19, 2012, 12:34:26 pm
The key to good interrupt handling is to make sure the code in the interrupt handler is as small as possible. IIRC the original RF22 lib had all kinds of stuff in their interrupt handler function, including reading data from the module, which meant everything else (like servos) had to stop when it receives a packet. When this coincides with a servo pulse, you have a glitch. I move the data reading outside so the actual interrupt takes almost no time.


Does you PPM code work on its own? Debugging these interrupt and timer issues are quite difficult! If you share your code I will have a look at it sometime this week. Can't promise anything though...
10  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: November 18, 2012, 09:45:31 pm
Hmm... are you using my modified version of the RF22 lib? Because I thought I solved that particular problem, my servos seem fine. Try the new code, and see what you get. I will investigate a bit more. I guess I could think about adding PPM out, but because I implemented autopilot directly on the receiver, I never had the need... It might be simpler to have the receiver talk to multicopter FC directly over serial port instead of the convoluted digital->PPM->digital thing.

Also, my new telemetry code is not fully tested!! Make sure you don't put it on something expensive! And because the rx defaults to transmit telemetry data at full power, make sure you have an antenna on the receiver all the time!

My RSSI values are very stable, down to the last digit. The trick is the read RSSI right after receiving a packet, otherwise it will be wrong.
11  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: November 18, 2012, 12:48:15 pm
Here is the new code with hardware servo, hardware tone, telemetry, and updated RF22 library

By default, pin 5 generates a tone for RSSI warning and bad packet. I'm using a piezo buzzer in series with a 1k resistor.

Currently the tones are:
4000Hz tone for bad packets
2000Hz tone for RSSI warning

Frequency and duration of the tone can be changed.

You can easily send more data back by modifying the telemetry data structure which is currently:

Code:
struct TELE_DATA_STRUCTURE{
  byte RSSI;
  byte RxBad;
  float Alt;
};

Just add your own variable in there.

12  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: November 14, 2012, 09:57:32 am
I donno much about the FrSky protocal, but that would be pretty cool. I was thinking about making an android app as well, but my app making skills is at the "hello world" stage.

How would you transfer data from the 9x to the phone? I was thinking some kind of bluetooth?

My telemetry is basically the same as my RC link, passing data structures directly, I will upload some example code this weekend. But if the FrSky is easy enough to implement and standard we should use it or at least have it as an output option. Being able to use the 9X to display telemetry is something I am also interested in.
13  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: November 11, 2012, 09:44:31 am
I'm not really a RF person. Actually, I'm not even really a electronics person! I just made simple dipoles from a SMA connector and coax cable.
14  Community / Exhibition / Gallery / Problem with my board! on: November 09, 2012, 11:59:31 am
Hi guys,

Just to let you know that I found a problem with my board design. It the way I am using the resistor dividers to shift 5V from arduino to 3.3V for the RFM22. Because I have modified the RF22 library to run at very high speed, the resistors and the capacitance of the traces begin to act like a RC filter. This can corrupt the SPI data, causing lockups. This means that the SPI bus is operating very close to the limit, voltage problems with power supply can easily cause a lockup, especially if you run a lot of servos. If you only use the board for spec scan or telemetry you may not have this problem at all.

As you can see here, the SPI clock out from arduino (blue) is distorted when it gets to the RF22 module (yellow). This screen shot is a bit exaggerated because I was using X1 probe, it's better with X10.




Solutions:

1. Software solution: reduce SPI speed, change the SPI speed down to 2MHz in the RF22.cpp file. Change the line in RF22::init() to SPI.setClockDivider(SPI_CLOCK_DIV8);
2. Hardware solution: reduce resistor values. I tried halving the resistor divider values (R2 - R7), and it works much better. Replace 1K with 470 Ohm, and 1.5k with 680 Ohm.
3. Both. <-- I recommend this for best reliability
15  Community / Exhibition / Gallery / Re: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module on: October 25, 2012, 04:25:50 pm
$110 is a lot of money. I don't think he will be able to sell many at that price considering that you can just get this: http://www.hobbyking.com/hobbyking/store/__24965__RMILEC_TS4047_10CH_2_5W_UHF_Module_System_w_Receiver_JR_module_.html $180 with diversity receivers.

A bit of a update, I lost my glider while testing autopilot. Stupid mistake, pulling too hard out of a dive. So I had to get a new one, spent all summer trying to get that flying. During that flight I was able to log RSSI vs distance, you can see the plot. I didn't go very far, only 200m, but if I extrapolate the trend I will probably start to get occasional packet drops at 1km and lose signal completely at 10km.

On the RF22 front, I have managed to get telemetry working on my boards, and fixed some bugs, unfortunately also introduced some new ones that causes the board to lock up randomly and other weird problems.
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