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Revo with Mavlink
« on: November 20, 2019, 03:52:52 pm »
Hello Everyone,

This is my first post in here, so don't be harsh on me.

I have a Revo Mini and I am trying to set up this FC board for different kind of aircraft types. But in this situation our platform is Conventional Heli (120 degrees FBL).

For the last update of LibrePilot there is a statement

"New telemetry protocols:
    MSP, MAVLink. OSD devices that use those protocols may now be connected directly (e.g.: minimosd with MWOSD).

And I want to use this Revo Mini with this telemetry hardware which link lays below.

Here is the question.

Is this possible?
Or is there any kind of video or informing data about this issue.

thanks in advance
happy to be here!  ;D

Re: Revo with Mavlink
« Reply #1 on: November 22, 2019, 07:08:17 am »
I might be wrong, but it's my understanding that LP's MSP and MavLink are designed to be used for OSD's that need these protocols.  I don't think there is any support for these as telemetry in the LP GCS.  If that is the case, then you would have to use something like QGCS with this.  There are a large number of maybe's there and it's likely that this setup won't work, but again, I haven't tried it.  I don't like the built in antenna on one of them..

I can tell you that long ago I did something similar.  I configured an FC port as "Telemetry" and connected a half duplex link, configured as a simple serial link and got that working.  It was slower than a regular OpLink setup because the link was not smart enough to understand the protocol and know which end should be sending.  An older version of something like this (500mw and with good antennas)?  Beware, this link says 500mw here and 100mw there; and 915MHz here and 433MHz there.

Assuming that the reason you want this is 915MHz, if I had to do it today, I would replace the RFM22B's on the FC and OpLink with a 915MHz version, and use 'next' which has 915/866/433 support.  Replacing the RFM22B's needs some special equipment (desoldering / reflow station, kapton tape) and excellent soldering skills.
« Last Edit: November 22, 2019, 07:17:18 am by TheOtherCliff »


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Re: Revo with Mavlink
« Reply #2 on: November 22, 2019, 06:52:02 pm »
Hello TheOtherCliff,

Thanks for quick response.

Actually I forgot to tell some specifics about the application.

I just want to see the data of the heli on GCS (if possible LibrePilot) by using the telemetry set which I sent it before. I thought that it is similar to what you did long time ago.

And I don't have any preference about the frequency of telemety. I have both of them (433 mhz and 915 mhz)

What I have done till now it following,

1st - Revo mini is booted by ardupilot and I connect this telemetry, It worked right away without any alteration on QGCS and MissionPlanner.

2nd - Revo mini with standart firmware is connected this telemetry, and tried to work on QGCS and MissionPlanner didnt work!

3rd - Revo mini with standart firmware is connected this telemetry, and tried to work on LibrePilot didnt work!

Btw I need to tell you that, Every possible port like FlexiPort and MainPort were tried by configuring Telemetry and Mavlink settings but still didnt work!

To sum up, I want to send aircraft information to computer by a telemetry set other that oplink.

Thank you all!

Re: Revo with Mavlink
« Reply #3 on: November 24, 2019, 04:49:25 am »
OpLinks work very well but there is an issue with the Revo Mini versions of OpLink (Air and Ground).  I personally have had this issue.  I really would try to sort this issue and use OpLinks if you intend to use LibrePilot.

The issue is that these OpLinks (and some others, and maybe some FC's too) have a bad brand of RFM22B (RF board).  So call these Bad and call the ones with good RFM22B boards Good.  Good works with Good, and Bad works with Bad, but Good does not work with Bad.  One or more of the "channel hopping channels" are not on the correct frequency, but when you use Bad with Bad, they both use the same (wrong) frequency, so it works fine.

Set up both ground and air the same way except for what must be different (coordinator or not, coordinator ID, device ID).  Also, you must be using the same version (e.g. 16.09) on both ground and air.  You can sometimes get away with different versions, but not when the versions are as different as 16.09 and the current 'next'.

Here is a thread that describes the issue.  Just read the first post, it has been updated with current information.  You can see the drops in signal level even in 16.09.  To see the AFC correction that is happening too, you must be using 'next':
« Last Edit: November 24, 2019, 05:04:57 am by TheOtherCliff »