New FrSkyX protocol

Bozos wrote: Thank you very much for your answer. I did that too at the model setup. But what I set on the transmitter isn't in order the rssi to work at the transmitters telemetry? Doesn't my flight controller take the rssi value directly from the receiver from sbus?

Thought you already got it.
This rx has NO telemetry , hence the transmitter is not involved in this game.
The signal is generated by the receiver and can be grabbed from a pad on the pcb or with special versions of firmware from
the sbus signal. So the flight controller and his set up is the part you have to inspect.

Hello

I am using a Frsky G-RX8 receiver with the Frsky x protocol on my devo 12s
All seems good but I cannot reset the telemetry altitude. Each time I bind the rx the altitude is 15 m or so.
Is it a way to reset this value ?
Thanks for help.
Morlacus

The code takes the first altitude telemetry value received and subtracts it from all the following altitude values. The intent is to display the value as above ground level.

So maybe the first altitude value received is not accurate - some small value perhaps. Do you have an FTDI adapter or logic analyzer to capture the telemetry from the trainer port? If not I can make a test build or two to figure out what's happening.

Anyone else have the same experience with any frsky altitude sensor?

@hexfet,

I have exactly the same as Moriacus, I have two G-RX8 receivers.
What is strange is that the altitude offset is quite consistent, one is always around 15m and the other around 35m.

Thanks. Please make a test with this test build (9b44f22). The "ground level" value will appear in the VOLT3 telemetry position. First test with the receiver off - the value should be zero. Then turn on the receiver and check what the value is after the altitude telemetry becomes valid.

Also do the altitude values start immediately around 15 (or 35), or do they take a few seconds to reach that value?

Hello
I have tested the build
The V3 shows 0 before turning on the Rx.
With Rx on it shows 113 and the altitude is approx 11 meters
the value of the altitude comes apparently immediatly
Regards
Morlacus

@hexfet,

Same for me, V3 shows 0 before turning on the Rx.
With Rx on it shows 118 and the altitude is approx 13 meters immediately.

Very strange. The two numbers should be the same magnitude, but seem different by a factor of 10. Was confused by another test...

What is the altitude above sea level where y'all live?

The test build is updated (same build number) with a protocol option named ALT TEST. Setting this to Enabled will reset the internal "ground level" value to zero. It will then be set internally to the next received altitude value, which should cause the displayed altitude to stay near zero. Let's see what the VOLT3 value becomes after using this option. Please take a screenshot.

The protocol option will immediately be set back to disabled by the protocol code, so don't be surprised if you don't even see it displayed as Enabled. Choosing enabled will still reset the saved ground level.

Hello
I have tested the new build.
The altitude of my workshop is approx 55 m.
The altitude given by the rx is approx 11 to 15 m (could differ according to the weather conditions of the day)

When enabling the Alt test resets the altitude in the alt box to zero. the V3 shows 137 or so.
When turning off the Tx or the Rx alone (the other is on) the altiude is kept when the other is turned on.
If both Tx and Tx are turned off, when turning on both, the altitude shown is the same as before reseting (11 this morning)

So it would be necessary for the moment to reset the altitude each time. May be it would be good to have this possibility left in the protocol.
Regards
Morlacus

It sounds very much like the very first telemetry value is low. Setting the ground level value after some time works to show ground altitude as 0. I'm not sure why the numbers don't match up more exactly (113 + 11 is not quite 137) but it's easy enough to test.

I'd prefer to keep setting the ground level automatically. Resetting it through a protocol option is awkward and frskyx is already at max number of options. I couldn't find any information about how often the altitude telemetry value is sent. The test build is updated with the ALT TEST protocol option changed to be the number of altitude telemetry samples received before setting the ground level value. Please test to find a value where the altitude telemetry value goes to zero after a short time (maybe 2 seconds) after powering on the receiver. When changing the ALT TEST value the tx must be turned off and on to use the new value.

Which brings up another question. With the current test firmware what volt3 value is shown if the receiver is powered off after it's been on for a while, then the ground level reset with the protocol option, then the receiver powered on again? Does the ground level still get set to about 113, or is it the higher value when the receiver is warmed up?

Thanks for the testing!

Hello

The V3 value shows allways a red box with 0V
The alt shown this morning without doing anything is approx 11m

I did the following procedure
Tx on RX on alt :11 approx

Tx on - RX on - set alt test to zero - Tx on - Tx off - alt telem :0 - Tx off - Rx off - Tx on - Rx on - Alt telem 11 m approx
Tx on - RX on - set alt test to 1 - Tx on - Tx off - alt telem :0 - Tx off - Rx off - Tx on - Rx on - Alt telem 9 m approx
Tx on - RX on - set alt test to 2 - Tx on - Tx off - alt telem :0 - Tx off - Rx off - Tx on - Rx on - Alt telem 7.5 m approx
Tx on - RX on - set alt test to 3 - Tx on - Tx off - alt telem :0 - Tx off - Rx off - Tx on - Rx on - Alt telem 6 m approx
Tx on - RX on - set alt test to 5 - Tx on - Tx off - alt telem :0 - Tx off - Rx off - Tx on - Rx on - Alt telem 4 m approx
Tx on - RX on - set alt test to 8 - Tx on - Tx off - alt telem :0 - Tx off - Rx off - Tx on - Rx on - Alt telem 2 m approx
Tx on - RX on - set alt test to 10 - Tx on - Tx off - alt telem :0 - Tx off - Rx off - Tx on - Rx on - Alt telem 0 m approx
Tx on - RX on - set alt test to 50 - Tx on - Tx off - alt telem :0 - Tx off - Rx off - Tx on - Rx on - Alt telem 0 m approx

So from 11m the alt test has to be more than 10. A alt test automatically set to the first value or an average of the ten or so frist values sent by te Rx would be good.
Regards
Ps I wonder if there is a spare for the main switch of a Devo 12 S

Thanks for all the testing When the alt test value is set to 10 do you see the altitude value as zero right away or does it move from 11 down to 0? Trying to get an idea of how long it takes to receive 10 altitude values from the receiver. Seems like we can find a workable value. From these results I'd like to set it a little larger than 10 if it doesn't cause too much delay. That should give some margin in case other altitude sensors behave a little differently.

hello

The altitude value changes very rapidly on the telemetry screen I would say probably more than 10 times by second. If it is the same rythm than the vario, it is very fast, the vario display is hard do read due to the change speed.
may be for a better accuracy you could leave the firsts 5 values (even if I have never seen weird values)
Regards

Hexfet,

I need to set Alt test to 20 to get a value below 1m
With 'alt test' at 10 I read 1.63m
with 'alt test' at 0 I read 12.8 m

With 'Alt test' at 50 it takes alraedy about 6sec before having an altitude and still not totaly at 0.

is it possible to wait 10 cycles and deduct 1m ?

Hello
Is there need for new test or a decision taken on the reset ?
Will this be soon in a nightly build ?
regards
Morlacus

It seems the best option is to add some way to reset the ground level value. Haven't had a good inspiration for a UI design.

The results indicate the altitude value from the sensor takes some time to get to a steady value. It would be nice to know if the standalone vario sensor behaves the same, but still need a solution for the GRX8. If either of you have an FTDI adapter it would be helpful to get a capture of the telemetry.

OpenTX telemetry sets the "ground level" to the first altitude telemetry value received. The UI provides a way to reset the value to the current altitude. It also is reset if no altitude telemetry value is received for about 20 seconds.

One idea for deviation is to make some values on the telemetry test page clickable, with the action being to reset the value to zero. It seems possible but complicated. Another idea is to add a "reset telemetry" button to the model menu (possibly only if the protocol supports telemetry). This would reset all pseudo-telemetry values (like ground level, battery consumption, min cell value, etc). The things you'd want to reset between flights. I'm looking into these options - other suggestions welcome.

Hello
The clickable button would be a good idea, It would be simple also to have a reset button in the protocol page where was the alt test.

Hello
One more question on Frsky protocol
What is the best way to have the best tuning of freq fine ?
The manual says O or -41. At -41 i have no signal.
On the other hand the LQI stays at 127.
I have a signal for a freq-fine setting from -20 to 60. Is the best the average ?
Thanks for your advices

Yes, the best will be at the midpoint of those two values.