2.4Ghz Receiver Output Format

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2.4Ghz Receiver Output Format

Postby ADI » Sun Aug 08, 2010 9:54 am

Hi,
Standard PPM FM receivers output their 1-2ms pulses sequencially. ie. Only one output is active at any one time.
My question is: Are the 2.4Ghz receiver outputs of the same sequencial format, or is the start of each channel's output pulse transitioned simultaneously ?
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Re: 2.4Ghz Receiver Output Format

Postby RCModelReviews » Sun Aug 08, 2010 9:45 pm

It depends very much on the brand/model of 2.4GHz receiver.

Some receivers "group" their pulses so that several channels are output at once (good for CCPM setups on helis where you want all the servos moving in unison, without the small lag inherent with a sequential output).
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Re: 2.4Ghz Receiver Output Format

Postby ADI » Mon Aug 09, 2010 10:10 am

Hi Bruce,

Damn! .... That creates a bit of a problem. I was looking at upgrading to 2.4Ghz from 72Mhz FM for my quadrotor machines. http://homepages.paradise.net.nz/jameskea/
I currently tap off the raw PPM serial stream and feed this single output to a micro's input capture I/O pin for processing.
The idea was to re-serialise, for want of a better word, the 2.4Ghz Rx outputs via the standard 'alternate channel' 'OR' diodes/BC548 arrangement. This only works of course if data is sequential.
I was looking at using either FrSky module or a Futaba FASST system.
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Re: 2.4Ghz Receiver Output Format

Postby RCModelReviews » Mon Aug 09, 2010 9:47 pm

You could use a small PIC or AVR processor to serialize the servo pulses -- but you'd have to know how to program them.
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Re: 2.4Ghz Receiver Output Format

Postby soopy » Mon Aug 09, 2010 10:31 pm

I could be wrong but I'm sure I read somewhere that one of the FrSky receivers in fact had a sequential PPM stream present on the circuit board. If I can find the reference I'll post back.

EDIT: Here's where I saw it: http://www.rcgroups.com/forums/showthre ... st15468667 Chase Wu is affiliated with FrSky so chasing him up might be worth your while.
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Re: 2.4Ghz Receiver Output Format

Postby RCModelReviews » Tue Aug 10, 2010 4:14 am

As I recall they were considering making it available on one of their receivers but I don't know if they ever did.
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Re: 2.4Ghz Receiver Output Format

Postby ADI » Tue Aug 10, 2010 11:27 am

RCModelReviews wrote:You could use a small PIC or AVR processor to serialize the servo pulses -- but you'd have to know how to program them.


I was hoping to get away without doing this, but perhaps have little choice.

soopy wrote:EDIT: Here's where I saw it: http://www.rcgroups.com/forums/showthre ... st15468667 Chase Wu is affiliated with FrSky so chasing him up might be worth your while.


Thanks for the link soopy
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