Add Controls interface (v27) and simple_ctrls.py example

examples/simple_ctrls.py

@@ -0,0 +1,43 @@
+#!/usr/bin/python3
+"""
+Simple Controls example that sweeps the control surfaces and periodically puts the gear up/down
+"""
+import time
+import math
+from flightgear_python.fg_if import CtrlsConnection
+
+gear_down_child_state = True
+def ctrls_callback(ctrls_data, event_pipe):
+    global gear_down_child_state
+    if event_pipe.child_poll():
+        gear_down_child, = event_pipe.child_recv()  # unpack tuple
+        # TODO: FG sometimes ignores "once" updates? i.e. if we set `ctrls_data.gear_handle`
+        #  the next callback will still have the old value of `ctrls_data.gear_handle`, not
+        #  the one that we set. To fix this we can just keep our own state of what the value
+        #  should be and set it every time. I still need to figure out a clean way to fix
+        #  this on the backend
+        gear_down_child_state = gear_down_child
+    ctrls_data.gear_handle = 'down' if gear_down_child_state else 'up'
+    # set only the data that we need to
+    ctrls_data.aileron = math.sin(time.time())
+    ctrls_data.elevator = math.sin(time.time())
+    ctrls_data.rudder = math.sin(time.time())
+    ctrls_data.throttle[0] = (math.sin(time.time()) / 2) + 0.5
+    ctrls_data.throttle[1] = (-math.sin(time.time()) / 2) + 0.5
+    return ctrls_data  # return the whole structure
+
+"""
+Start FlightGear with `--native-ctrls=socket,out,30,,5503,udp --native-ctrls=socket,in,30,,5504,udp`
+"""
+ctrls_conn = CtrlsConnection(ctrls_version=27)
+ctrls_event_pipe = ctrls_conn.connect_rx('localhost', 5503, ctrls_callback)
+ctrls_conn.connect_tx('localhost', 5504)
+ctrls_conn.start()  # Start the Ctrls RX/TX loop
+
+gear_down_parent = True
+time.sleep(2)
+while True:
+    # could also do `ctrls_conn.event_pipe.parent_send` so you just need to pass around `ctrls_conn`
+    ctrls_event_pipe.parent_send((gear_down_parent,))  # send tuple
+    gear_down_parent = not gear_down_parent  # Flip gear state
+    time.sleep(10)

flightgear_python/ctrls_v27.py

@@ -0,0 +1,89 @@
+"""
+FlightGear Controls Network interface, version 27
+
+See https://github.com/FlightGear/flightgear/blob/619226e9d069d2a3e8ebf8658fb5441ca8a2c233/src/Network/net_ctrls.hxx
+"""
+
+from construct import Array, Enum, Const, Padding, Int32ub, Float64b, BitStruct, Flag, BitsInteger, Mapping
+
+RESERVED_SPACE = 25  #: Constant value from define
+
+FG_MAX_ENGINES = 4  #: Constant value from enum
+# FG_MAX_WHEELS = 16  #: Constant value from enum. TODO: Unused?
+FG_MAX_TANKS = 8  #: Constant value from enum
+
+# Big endian
+#: Ctrls v27 structure
+ctrls_struct = {
+    'version': Const(27, Int32ub),
+    '_padding0': Padding(4),  # TODO: Not documented, probably due to struct packing
+    'aileron': Float64b,  # -1 ... 1
+    'elevator': Float64b,  # -1 ... 1
+    'rudder': Float64b,  # -1 ... 1
+    'aileron_trim': Float64b,  # -1 ... 1
+    'elevator_trim': Float64b,  # -1 ... 1
+    'rudder_trim': Float64b,  # -1 ... 1
+    'flaps': Float64b,  # 0 ... 1
+    'spoilers': Float64b,
+    'speedbrake': Float64b,
+    'flaps_power': Enum(Int32ub, unavailable=0, available=1),
+    'flap_motor_ok': Int32ub,
+    'num_engines': Int32ub,
+    'master_bat': Array(FG_MAX_ENGINES, Enum(Int32ub, off=0, on=1)),
+    'master_alt': Array(FG_MAX_ENGINES, Enum(Int32ub, off=0, on=1)),
+    'magnetos': Array(FG_MAX_ENGINES, Int32ub),
+    'starter_power': Array(FG_MAX_ENGINES,
+                           Enum(Int32ub, off=0, on=1)
+                           ),
+    # throttle needs to be moved forward 1 double?
+    '_padding3': Padding(4),  # TODO: Not documented, probably due to struct packing
+    'throttle': Array(FG_MAX_ENGINES, Float64b),  # 0 ... 1
+    'mixture': Array(FG_MAX_ENGINES, Float64b),  # 0 ... 1
+    'condition': Array(FG_MAX_ENGINES, Float64b),  # 0 ... 1
+    'fuel_pump_power': Array(FG_MAX_ENGINES,
+                             Enum(Int32ub, off=0, on=1)
+                             ),
+    'prop_advance': Array(FG_MAX_ENGINES, Float64b),  # 0 ... 1
+    'feed_tank_to': Array(4, Int32ub),
+    'reverse': Array(4, Int32ub),
+    'engine_ok': Array(FG_MAX_ENGINES, Int32ub),
+    'mag_left_ok': Array(FG_MAX_ENGINES, Int32ub),
+    'mag_right_ok': Array(FG_MAX_ENGINES, Int32ub),
+    'spark_plugs_ok': Array(FG_MAX_ENGINES, Enum(Int32ub, fouled=0, ok=1)),
+    'oil_press_status': Array(FG_MAX_ENGINES,
+                              Enum(Int32ub, normal=0, low=1, full_fail=2)
+                              ),
+    'fuel_pump_ok': Array(FG_MAX_ENGINES, Int32ub),
+    'num_tanks': Int32ub,
+    'fuel_selector': Array(FG_MAX_TANKS, Enum(Int32ub, off=0, on=1)),
+    'xfer_pump': Array(5, Int32ub),  # specifies transfer from array value tank to tank specified by int value
+    'cross_feed': Enum(Int32ub, off=0, on=1),
+    '_padding4': Padding(4),  # TODO: Not documented, probably due to struct packing
+    'brake_left': Float64b,
+    'brake_right': Float64b,
+    'copilot_brake_left': Float64b,
+    'copilot_brake_right': Float64b,
+    'brake_parking': Float64b,
+    'gear_handle': Enum(Int32ub, up=0, down=1),
+    'master_avionics': Enum(Int32ub, off=0, on=1),
+    'comm_1_MHz': Float64b,  # TODO: Frequencies are all screwed up. Garbage data
+    'comm_2_MHz': Float64b,
+    'nav_1_MHz': Float64b,
+    'nav_2_MHz': Float64b,
+    'wind_speed_kt': Float64b,
+    'wind_dir_deg': Float64b,
+    'turbulence_norm': Float64b,
+    'temp_c': Float64b,
+    'press_inhg': Float64b,
+    'hground_m': Float64b,  # ground elevation
+    'magvar_deg': Float64b,  # local magnetic variation
+    'icing': Int32ub,
+    'speedup': Int32ub,  # integer speedup multiplier
+    'freeze': BitStruct(  # Default is big-endian
+        other=BitsInteger((Int32ub.sizeof() * 8) - 3),  # Rest of uint32 minus the 3 flags
+        fuel=Flag,
+        position=Flag,
+        master=Flag,
+    ),
+    '_reserved': Padding(Int32ub.length * RESERVED_SPACE),
+}

flightgear_python/fg_if.py

@@ -88,8 +88,9 @@ def _fg_packet_roundtrip(self):
         except ConstError as e:
             raise FGCommunicationError(f'Could not decode FG stream. Is this the right FDM version?\n{e}') from e
 
-        # Fix FG's radian parsing error :(
-        s = fix_fg_radian_parsing(s)
+        if isinstance(self, FDMConnection):
+            # Fix FG's radian parsing error :(
+            s = fix_fg_radian_parsing(s)
 
         # Call user method
         s = self.fg_rx_cb(s, self.event_pipe)
@@ -144,6 +145,24 @@ def __init__(self, fdm_version: int):
         self.fg_net_struct = Struct(*[k / v for k, v in fdm_struct.items()])
 
 
+class CtrlsConnection(FGConnection):
+    """
+    FlightGear Controls Connection
+
+    :param ctrls_version: Net Ctrls version (27)
+    """
+
+    def __init__(self, ctrls_version: int):
+        super().__init__()
+        # TODO: Support auto-version check
+        if ctrls_version == 27:
+            from .ctrls_v27 import ctrls_struct
+        else:
+            raise NotImplementedError(f'Controls version {ctrls_version} not supported yet')
+        # Create Struct from Dict
+        self.fg_net_struct = Struct(*[k / v for k, v in ctrls_struct.items()])
+
+
 class PropsConnection:
     """
     FlightGear Telnet Interface Connection (also known as the property interface).