dora-node.yml is the typed contract a consumer wires against, and the only one
they get: no source package is shared between node repositories. The jog,
request and ui ports stay untyped, because dora treats a port carrying
request_id as pattern-correlated and several Arrow schemas legitimately flow
over each — one per service, one per console message.
dataflow.yml runs the whole operator stack from checkouts: this node, the
WebSocket bridge and the arm.
web/ holds a placeholder page, not the real console. It exists so the dataflow
has something to serve and so the node can be checked end to end before the
Control section is ported across from the monolithic repo. It reads telemetry
and can take, release and stop; nothing else.
The reader owns the pad on a thread of its own, and nothing outside that file
may touch pygame: everything else sees a plain immutable Sample. That is what
lets the rest of the node be tested with no hardware, and what keeps SDL's
quirks out of the arm logic.
Sample.present is the field that matters. A pad that has been unplugged reads as
absent rather than as centred, so "the operator let go" and "the pad fell off
the desk" stay distinguishable — they call for the same stop, but only one of
them is worth logging.
Only the display and joystick subsystems are initialised. pygame.init() also
opens audio, which on a headless robot fills stderr with ALSA errors for a
device this node never uses; the display is needed despite there being no
window, because SDL refreshes joystick state during the event pump.
Settings are parsed once at startup so a deadzone that would silently make the
pad inert stops the node before it joins the dataflow.
cristhian