Possible incompatibility with the older 8-Channel XPS receiver and OpenTx and XJT-D16
#1
Jim,

I have a perfectly working Nano/X10+v2 setup with a Jumper T12 Pro transmitter running OpenTx 2.3.10 and XPS XJT-J1 firmware v4.4.

I wanted to use the X10+v2 in another plane so I replaced the Nano/X10 with one of my older 8-channel XPS receivers.

I first used the push button method to set the factory defaults in the 8-channel receiver.  Then I verified the country code was #1 for USA.  Then I configured all of the channels for failsafe user-settable.

The 8-channel receiver binded successfully to the transmitter and all of the servos worked, until I noticed some random loss of control on all channels.  I first thought I had the transmitter located too close to the receiver and was swamping the receiver, but that was not the case.  I moved to about ten feet apart and still observed the random loss of control.  With the range check button on the Tx module pressed I could get no more than about one foot of effective range!
 
I tried another older XPS 8-channel receiver with the same loss of control result.

Then I tried the Nano/X10 again and with the same transmitter it worked perfectly.

Then I tried binding the older 8-channel XPS receiver to my Futaba 9C transmitter with its XPS Tx module and it worked perfectly.  That gave me an idea:

I configured the Jumper T12 and XPS-J1 module to use PPM instead of XJT-D16 and it now worked perfectly with the older 8-channel XPS receiver.

So I think there is some incompatibility between the older XPS 8-channel receiver, and OpenTx, XJT-D16, XPS-J1.

What do you think?

Thanks,

Paul

(yes it was raining all day so I had time for this sort of thing)
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#2
This could be an issue with the frame rate being too fast for the older receivers.  Keep in mind that you can NOT change the number of channels or frame rate in the transmitter *after* a bind has occurred or you will experience the exact same thing with any of our receivers.  The frame rate and number of channels is stored in the receiver itself, and that information is used.  If that changes, the hopping sequence will go in and out of phase, resulting in lost packets.
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#3
Ok, interesting. It's all good, I'll use PPM which works fine.

Thanks Jim, Paul
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