GPS

Overview

ExLocation asks the modem's GNSS engine for a position once per second. It needs the modem firmware running, and a clear view of the sky: go outside or sit by a window. The first fix can take a few minutes.

Tracker state

ExLocation.state()

:tracking means the GNSS engine is running. :starting means it is still waiting for the modem.

Satellites in view

ExLocation.satellites()
|> Enum.map(&Map.take(&1, [:system, :sv_id, :status, :elevation, :azimuth]))

Current position

ExLocation.get_position()

{:error, :no_fix_yet} means there is no fix yet; wait and run it again.

Follow the position

Prints each new fix for 60 seconds.

ExLocation.subscribe()
frame = Kino.Frame.new() |> Kino.render()

# 60 rounds; each waits up to 1 second for a message from ExLocation.
for _round <- 1..60 do
  receive do
    {ExLocation, :position, fix} ->
      text = "#{fix.latitude}, #{fix.longitude} (#{length(fix.satellites_used)} satellites)"
      Kino.Frame.render(frame, Kino.Markdown.new(text))

    {ExLocation, _other, _} ->
      :ok
  after
    1_000 -> :ok
  end
end

ExLocation.unsubscribe()