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Homemade On board telemetry System

Discussion about Tx, Rx, Servo's, Batteries, Chargers, and all the other things we like to talk about..
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Jimbo,
I hope I am not too late, but I assume that you will do normal R/C range checks before you try to fly with your telemetry test setup.
Do the check both without the telemetry transmitting, then with, to see whether there is any impact on the R/C Rx when this is operating on minimum signal.
I hope to range check my higher power 433MHz test setup by the end of this week.
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Jimbo,
Managed to carry out a basic range check today using two RFM69CW 433MHz modules sending 10 byte payload packets at an RF data rate of 9600baud & using simple 173mm wire monopole aerials at each end.
With this setup, I got successful data packet reception and Acknowledge loop up to 300m range with clear line of sight transmission over flat ground. Both radios at similar height of just over 1m & both aerials in same axis (vertical).
The RFM69CW devices push out 13dBm (20mW), but there are also physically identical RFM69HCW devices available which push out 20dBm (100mW). Receiver sensitivity is down to -118dBm depending on RF bit rate.
Range will be better with a full dipole aerial.

I have also spotted that a UK outfit called HASNET sell very small bare PCBs for about £1 each, which take both a RFM69 module and an atMega64/328 DIL processor, so that may be an alternative to an Arduino Mini plus RF device.
Peter
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jimbo
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Re: Homemade On board telemetry System

Post by jimbo »

Is this the one?
http://www.hobbytronics.co.uk/rfm69cw-w ... 7QodHPMHow

Hope to get a fly soon, winds shifting back SW, so just hoping on a clear not too cold weather window.
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Jimbo,
Yes, that is the one, although I went for the breakout version at just under a tenner each in order to ease interfacing to an Arduino Uno as the breakout module has the relevant interface pins on a 0.1" pitch and includes both 3.3v regulator and level conversion, making it 5v Arduino compatible.
By the way, I have just fitted SMA jacks to my breakout units (although not specifically designed to do this), so can now fit alternative/commercial antennae.
The 14 pads on the standard module are on a 2mm pitch.
That webpage gives you links to the data sheet, the RFM69 Arduino library and a sample sketch that works straight away on an Arduino rather than the Moteino (Arduino clones with built in RFM69 + flash chip) as the standard LowPowerLabs sketches assume the presence of a flash chip. However, the sketches are easy enough to modify to delete the relevant flash library bits.
The library is good as it allows you to control almost all aspects of the device if you want to.
The library device initialisation default is to use FSK modulation & packet transmission with a RF bit rate of 55,555bps.

It will be interesting to see what you get with your existing setup as a first step.
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Very impressive AJH,
The Manchester encoding system gives a guaranteed logic level transition on every data bit & can be used for automatic data clock recovery at the receiving end, but also gives smaller DC offset variations on the received signal (as there are as many short term highs as lows in the data stream), thus making it easier to reliably decode the data stream.

Thanks for the tip on the FRSky SPort protocol. I had just googled it and there are several leads - including an Arduino library available on GitHub which Jimbo may want to look up.
Having the ability to use the range of commercially available sensor units would be a big bonus.
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jimbo
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Re: Homemade On board telemetry System

Post by jimbo »

Currently i do not use a protocol. Currently just transmitting a float. Quick n dirty. Using virtual wire and the LCD driver that's all.
If it is successful regarding the range, the plan was to add the GPS write some proper code.
Nice ajh, Some electronics in there. Is that just four the receiver?
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jimbo
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Re: Homemade On board telemetry System

Post by jimbo »

All this talk of FRsky... I have a 9xii currently in the garage, would i be able to get the 9xii to display the telemetry information from various sensors, if i buy this modeule? Or is only for half dulplex ie out to the glider, ie does the 9x2 provide a method to show the telemetry data?

https://www.t9hobbysport.com/frsky-djt- ... ter-module

Im guessing the tx doesnt have the facility to display the data?

EDIT - Just read that RCG thread above :)

I use a FrSky X8R telemetry enabled receiver and a FrSky DJT JR module with pins on the back, into which I can plug one of the FrSky FLD-02 telemetry displays :-)
IIt could be done with this
http://www.brchobbies.co.uk/catalog/pro ... ts_id=1485
I think i need to check and see if the 9x2 still works.
Last edited by jimbo on 08 Dec 2016, 18:25, edited 1 time in total.
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Jimbo,
I seem to recall that it is possible to upgrade the 9x transmitters to be able to change the firmware (say to OpenTx) and also to change the inbuilt RF unit to an FRSky XJR module. I think that the XJR module then allows 2 way operation, but only in D8 telemetry mode. I can't recall what happened about telemetry data display.
I think I upgraded my old unit using a Smartie parts module to upgrade the firmware and take the XJT module.
Try googling '9x upgrade'.
Barry_Cole

Re: Homemade On board telemetry System

Post by Barry_Cole »

AAAAAAAAAAAAAAAAAAAAAAAAAhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

8-) 8-) 8-) 8-)

BC
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Peter Balcombe
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Re: Homemade On board telemetry System

Post by Peter Balcombe »

Jimbo,
I have just reminded myself what I did when I upgraded the 9x transmitter!!
I added both the programmer and telemetry upgrade options & made this easier (with the solderless method) using two SmartieParts products (Programmer & TelemeryEZ - now replaced by an all in one board at $70!.
The programmer allowed OpenTx to be loaded & the telemetry option replaced the inbuilt Tx with a FRSky XJT unit plugged into the standard module slot.
The mod then used the serial data XJT connector on the rear of the module to get at the telemetry data, which was fed back into the 9x to the Smartie Parts module for display on the normal LCD.
I know that I used this successfully with an FRSky X8R receiver and altimeter sensor - although no voice/audio output.
However, although this gave a much more useable system with telemetry, the switches/pots available on the 9x were a bit limited, so stuck to my Futaba FF9 + FRSky modules without telemetry until I got my hands on a Taranis (settle down Barry!!)
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