Telemetry Forwarding

Unmaintained Article Please check the manual for more up-to-date information.

Introduction

Forwarding to intended to be used where you want to send the data received by mwp from the aircraft on to another device. Typically this would be an antenna tracker that improves the range of the video / telemetry radio / long range control radio system.

So in the daigram, mwp (ground station) and the aircraft exchange data by means of a telemetry radio system (3DR, HC-12, LoRA, proprietary systems such as CRFS or DragonLink). Typically this is used pre-arm for pre-flight checks (sufficient satellites, sensors working etc.) and upload / verification of a waypoint missions, using bi-directional MSP (Multiwii Serial Protocol) messages.

When armed, the telemetry system receives telemetry data (flight monitoring data) from the aircraft which is displayed on the ground station. For iNav, this is typically and most efficiently done using LTM (Lightweight Telemetry), a unidirectional protocol that is pushed from the aircraft.

In order for the antenna tracker to do its job, it also needs some of the telemetry data in order to position the antenna (aircraft position / altitude at least). mwp forwarding provides the capability to forward some or all of the telemetry data to the secondary device (the antenna tracker). mwp telemetry forwarding provides a flexible approach; there can be different baud rates between the air and ground sides and selective filtering according to defined settings can be imposed (the default being to forward only the LTM subset common to iNav and the open source antenna tracker Ghettostation. If you elect to forward all received data (both MSP and LTM), then the data from uploaded mission verification would be forwarded as well, but this is a side affect rather than an expected use case.

mwp can forward either LTM or Mavlink to a ghettostation.

Settings

Forwarding device

The forwarding device is a command line option, using standard mwp device notation:

mwp --forward-to 00:14:03:11:35:16 # A BT device address

mwp --forward-to /dev/rfcomm1@9600 # BT device node, with baud rate (9600)

mwp --forward-to udp://wol:3000 # for those of us with computers named after 'pooh' characters

If you only ever use the same device, it can get set in ~/.config/mwp/cmdopts:

# Default options for mwp
--rings 50,20
#--wayland
--forward-to 00:14:03:11:35:16
--dont-maximise
-S 5000

Note that while the two serial devices do not need to run at the same baud rate, you should ensure that they can both support the needed data rate. It is also the case that Mavlink requires at least 19200 baud.

Message to forward

The type of messages to forward to the --forward-to device is a dconf / gsetting value forward.

$ gsettings range  org.mwptools.planner forward
enum
'none'
'LTM'
'minLTM'
'minMAV'
'all'

The min* variant sends just the data necessary for antenna tracking, rather than everything received.

Or in dconf-editor