OpenLRS - Opensource Radio Control System form Flytron - RC Groups
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May 28, 2011, 05:34 AM
MelihK's Avatar
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OpenLRS - Opensource Radio Control System form Flytron

important: You can find similar topic here. CrashingDutchman already opened a topic about OpenLRS but i need a new topic for sharing codes and updates in the first post of topic. Thanks for your understanding.

Hi Everyone,

Maybe you know, i'm working on an opensource RC system since 1+ years.
It's name was OpenFARC at the start, but we learned FARC is a terrorist group from 70's, then name changed to OpenLRS.

OpenLRS Rx and Tx based on an Atmega328P microprocessor with Arduino compatible boot and RFM22B 100mW 433Mhz RF module.

OpenLRS Receiver

This is the Rx module of OpenLRS. (RFM22B rf module is the bottom side of the PCB)

  • Serial Port for firmware upload and telemetry application
  • 3.3v I2C port for all modern sensors as WiiMotionPlus, WiiNunchuk, MEMs gyros, accelerometers, barometers, etc.
  • 8 channel servo output or PPM Sum(serial PPM) ourput with one jumper configuration.
  • PWM out for RSSI output. (You can modify it for 9th channel)
  • Red and green LEDs for visible informations
  • RFM22B tranceiver module including Si4432 chip with configurable 0-100mW output, Frequency hopping capability and hundreds features.
  • 16Mhz Atmega328 processor with Arduino Pro Mini compatible bootloader.
  • RF module works bidirectional and possible to send Telemetry data to the ground.
  • 2048 step servo resolution (11 bit)
  • 50Hz servo refresh

A sample video about it's flexibility. You can add a Wii Motion Plus board (10$) for 3 axis gyro stabilized plane
OpenLRS + Wii Motion Plus (0 min 51 sec)

For PPM Sum mode, just plug a binding plug (jumper) between Channel 1 and 3. That's all you need for using it with autopilots or multicopter controllers.

OpenLRS Transmitter M1 Module

  • Serial port for firmware upload and telemetry application
  • a buzzer for audible information
  • bi color led for visible information
  • RFM22B tranceiver module including Si4432 chip with configurable 0-100mW output, Frequency hopping capability and hundreds of other features
  • 16Mhz Atmega328 processor with Arduino Pro Mini compatible bootloader.
  • Low Power (+1dBm) mode for range test (Press and hold the button when Power on your Tx)

Inside of M1 Module

We are sending it with Futaba module case, but you dont need a futaba transmitter for using it, just connect PPM, Battery and ground wires to your transmitter

7W Booster

Our 7W booster board is the "L" letter of the OpenLRS
We designed the OpenLRS Tx and Rx modules for daily usages and their output power is only 100mW max (you can reduce it from firmware).
If you need really "long" range, you should order this booster.
By the way, booster is not a good option for daily rc flights, this is why we have different topic for it.

Joining the OpenLRS community

with default firmware, It works like a standard RC/UHF systems and only helps for using 2.4 video transmitters on your FPV setup. Not a big deal for an opensource project.

We are searching for Arduino developers, if you are, come and join us.

Product page:
Forum pages of OpenLRS:
Google Codes Page:

Thanks for reading
Last edited by MelihK; May 28, 2011 at 05:43 AM.
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May 28, 2011, 09:36 AM
Registered User
First notice: about PPM approach, same issue appeared before to Frsky receivers, and they changed approach based on this advice:
- Some controllers does not decode all channels, only first 4-6
- most HT use channels 7 and 8 to operate
- as a result, using as PPM output channel 8 will drop HT support for such setups.
- what to do: move PPM to other output, and provide decoded channels 7 and 8 (at least) on their corresponding ports.
Easy to do, it's software only
Last edited by renatoa; May 28, 2011 at 09:46 AM.
May 28, 2011, 01:33 PM
MelihK's Avatar

You right. I will share a new and more readable code in this week. And PPM generator code will be change with more Arduino versions because current code including low level AVR-GCC commands and not for newbies.

I found a problem on serial PPM code, current code working like serial servo signals (1500ms high + 300us low + ....) and Multicopter boards reading only rising edges of the signal and calculating 1500+300 = 1800ms. I will change the serial PPM part of code with compatible one.
May 29, 2011, 05:18 AM
Registered User
Mine arrived yesterday and a quick test shows it works 'right out of the box'.

However, when bench testing, I get some red LED flashes on the Rx and the servos stop momentarily - Melih, we need some basic manuals for the Tx and Rx - like now!!

My interest is not for super long range, but because it's opensource and has the possibility to change the frequency because in the UK we are legally allowed 459MHz for airborne control.

The HopeRF module will need some component changes to match the Tx PA at 459MHz, but is something I can take care of.
Better still would be to swap out a HopeRF module for 470MHz as 459MHz is within it's Tx range.
Melih, can you get the HopeRF 470MHz module?

May 29, 2011, 09:56 AM
Registered User
wallaguest1's Avatar
is not too much 1 dBm or a range test? maybe 0.1 mw would be more adequate ?

the hole visible in the module is there for any reason? its in the opposite side of the antena
May 31, 2011, 04:39 AM
Registered User
Such little interest in this?

Maybe I'm not surprised as everyone seems to want a complete 'ready to go' solution these days and not so many are really interested in experimenting/developing for themselves.

This has so many possibilities with the right community developing ideas.
Integrated gyro stabilisation, telemetry etc....

Perhaps make a post over in the MultiWii/Arduino forum where there are some keen people who are happy to share and several with good Arduino experience

Is the product better called OpenUHF because OpenLRS does nothing for me?

May 31, 2011, 04:44 AM
Registered User
I am still waiting the kit from MelihK

Yes, the name is a bit misleading, because it's not intended to be a true LRS, rather medium range.
May 31, 2011, 05:01 AM
Flying like an Angel.
BlueAngel2000's Avatar
Yes, i find it somehow disturbing, why some really good products or technical solutions are not that pushed by the community, instead of the "what do i need for ultra long range newbies" threads.

Especially for the Multicopters this LRS is a very good solution.
1. stay on the legal side in europe with the 10mW setting
2. fly with legal 10mW 2,4Ghz video link

Because 35MHz is not perfect for copters and 5,8G video too.
May 31, 2011, 05:36 AM
Registered User
Some of my observations:

1) Melih, you really need to take a gamble and have more units ready for despatch and faster delivery - I would pay a few dollars more for quicker delivery. This project may die a death if people can't get the hardware quickly and you are the sole agent for this (possible small gold mine).

2) The product title of LRS is maybe not so good, it is mis-leading, even with it's standard <=100mW - OK so you have the possibilty to add your 7W amplifier, now you can really get into the male genitalia size bragging contest!!

3) Add some expansion ports to the Rx board so that people can configure it to whatever they like.

4) In the UK, we can legally use 459MHz @ 100mW for airborne model control - there is currently no commercial product available (other than the EZUHF with special UK firmware, and it's closed source).

5) Who knows what more is possible ???

May 31, 2011, 08:56 AM
Registered User
Yeah it would be nice to see some fpv footage with the standard unit to see how much range it would achieve...that would surely boost the sales
May 31, 2011, 09:46 AM
Don't leave it Stock
mrfliboy's Avatar
When mine arrives here in the states, I have aircraft ready to test range with. Just waiting for delivery. Expecting this week
May 31, 2011, 11:10 AM
Registered User
CrashingDutchman's Avatar
Here is how I connected my OpenLRS tx to my Sanwa (Airtronics) RD 6000 transmitter. The OpenLRS tx comes with a case that fits Futaba transmitters. At first I planned to use it without the case (or use a different case), but I have changed my mind (Melih, I owe you $ 10.00 )

From the schematic I found out that the pin config is like this for the Futaba connector (pin 1 is on the right side when looking at the back of the OpenLRS casing where the pins are):
1 - ppm
2 - pwr (can it handle 12V?)
3 - rf led (not used)
4 - GND
5 - Antenna (but not connected in schematic)

I used a 5 pin header and removed pin 3 and 6 by pullling them out. I soldered the 3 pins that were left on a piece of prototyping board. Then I used a piece of 3 strands wire from a defective ESC and soldered them to the header pins.

As you can see in the picture above, I used a piece of Velcro on the side of the prototype board and to the back of the OpenLRS casing. This way the OpenLRS is secured to the prototype board.

Below is how the prototype board and casing are attached to eachother.

Now I only have to find a good way to connect this to my tx. Will post when it is done.
Jun 05, 2011, 08:09 PM
Registered User
I'm thinking of getting the openlrs... but a few things are stopping me...:
eta on JR case? [lots of people, inc me, use turnigy 9x]

distance reports? + distance of the range check.. [im not wanting a very LRS, but want to get rid of 1.2/2.4 interference, and be able to fpv 2-4kms max]

tests with 900/1.2/1.4/5.8 systems?

weight of receiver?

any debugging features with the Arduino.. i have not used that mcu/bootloader before.. but plenty of other ones.. for general loading, i see a bit of info on your forum.

Jun 06, 2011, 02:22 AM
Registered User
About JR case, I suggeste here a solution how to use Futaba modules in a JR radio, and was adopted by MelihK, there will be an adapter board, not a real JR module:
Jun 06, 2011, 02:40 AM
Registered User
ahh. thats good.. i wonder how much it is/when it will be made.. otherwise i might just get 2 rx's..
Melih - have you/are you able to modify the code for the tx to run on the rx [i know you said it is possible, but i dont know if it has been done!]... i would rather have a fully working system which i can then tweak.. instead of having planes/copters dropping from the sky!

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