How to alert pilot to a relay output?

Daveemtb · October 9, 2023, 3:36pm

In the UAS I have, there is a fail-safe system which cuts the propulsion power when a certain radio link is lost. This is to limit fly-away. However, it takes careful monitoring from the pilot to notice when this has happened, so that they can follow the appropriate reset procedure.

The fail safe system has a normally open relay output which closes when this state occurs, and I’d really like to provide an obvious alert to the pilot when this happens. If I were to wire this to provide a certain voltage to an ADC or GPIO pin, is there some way of sending something to the ground station (Mission Planner) over the telemetry that would do this? Or alternatively could it trigger an alert on the MinimOSD that is used to overlay telemetry on the FPV video?

I imagine that there might be other applications for this for sensors etc.

Any ideas gratefully received!

geofrancis · October 9, 2023, 4:00pm

you will need to use a lua script to send an alert when the relay is triggered.

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/examples/hello_world.lua

-- This script is an example of saying hello

gcs:send_text(0, "hello, world") -- send the traditional message

Daveemtb · October 9, 2023, 4:26pm

Many thanks for your suggestion. Looking at Lua Scripts — Copter documentation it appears that the command for the output to pilot is probably:

gcs:send_text( severity , text )

I think I need to study the following regarding analogue input:

github.com

ArduPilot/ardupilot/blob/master/libraries/AP_Scripting/examples/analog_input_and_GPIO.lua

-- This script is an example of reading a analog pin, PWM in and GPIO

-- for these examples BRD_PWM_COUNT must be 0

-- load the analog pin, there are only 16 of these available
-- some are used by the main AP code, ie battery monitors
-- assign them like this in the init, not in the main loop
local analog_in = analog:channel()
if not analog_in:set_pin(13) then -- typically 13 is the battery input
  gcs:send_text(0, "Invalid analog pin")
end

-- load a input pwm pin
local pwm_in = PWMSource()
local pwm_in_fail = PWMSource()

if not pwm_in:set_pin(50) then -- AUX 1
  gcs:send_text(0, "Failed to setup PWM in on pin 50")
end

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I haven’t got my head around that yet but I’ll see what I can figure out.

Thanks again.