Thread: Rave Futaba T8J S-FHSS
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Old Aug 17, 2012, 05:14 AM
SimonChambers is offline
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Radio? Screwdriver!
United Kingdom, England, Bristol
Joined Aug 2011
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I've started reverse engineering the protocol. Not finished yet but I mostly understand it - its very simple protocol.

A few stats about the protocol for those interested:
Servo Data Range: 920 to 2121 = Range of 1201 points. (Probably 10-bit internally - 1024 units resolution - even if 11-bits internally, the protocol doesn't make use of it)
Hop Frequency: ~6.5ms to ~6.8ms
Number of Hop Channels: 31
Data Rate: 128.143kbaud
Modulation Format: 2-FSK

It appears that the channels that it hops on is not defined during Binding like other protocols (Hitec+FrSky), so the channel list must be/likely to be fixed. This is expected due to the lack of Bind mode on the transmitter. Unless there is a bind packet sent occasionally that I haven't seen yet. However the receiver does show an indicator to say its locked on but receiving the wrong ID (i.e. its locked on to the channel hopping of a transmitter, but it doesn't match the ID that the receiver is bound onto).

Data Rate is a lot quicker than I expected. I was imagining it would be quite low, as to help increase the range, given that the transmit power of the S-FHSS range is only ~60mW (iirc).

This is all preliminary, as I really need to get another S-FHSS transmitter to double-check all this.

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Last edited by SimonChambers; Aug 17, 2012 at 02:09 PM. Reason: Updated number of hop channels
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