The controller

parol6-server is the process that owns the robot. Start it on the PC the control board is plugged into, and leave it running; clients connect and disconnect as they like.

Starting it

parol6-server --serial COM5                # Windows
parol6-server --serial /dev/ttyACM0        # Linux
parol6-server --serial /dev/cu.usbmodem1   # macOS: ls /dev/cu.usbmodem* gives the name
parol6-server                              # no serial port: simulator mode
parol6-server --serial COM5 --log-level INFO

The options, from the source:

Option	Default	Meaning
--host	0.0.0.0	UDP host address
--port	5001	UDP port
--serial	—	Serial port (e.g., /dev/ttyUSB0 or COM3)
--baudrate	3000000	Serial baudrate
-v, --verbose	0	Increase verbosity; -v=INFO, -vv=DEBUG, -vvv=TRACE
-q, --quiet	flag	Enable quiet logging (WARNING level)
--log-level	—	Set specific log level (one of TRACE, DEBUG, INFO, WARNING, ERROR, CRITICAL)

The serial port can also come from the environment (PAROL6_COM_PORT) or from the file the controller saves the last port to, so that a second start needs no option. Once running, connect_hardware("COM5") from a client connects or re-connects the port, and simulator(True) switches to the virtual arm.

From Python

The Robot class starts and stops the controller as a subprocess, for scripts that should be self-contained:

from parol6 import Robot, RobotClient

with Robot(host="127.0.0.1", port=5001) as robot:      # starts parol6-server, waits until it answers
    with RobotClient() as rbt:
        rbt.wait_ready(timeout=5)
        rbt.simulator(True)
        rbt.home(wait=True)

Robot also carries the robot model (kinematics, limits, tools) that the clients use for previews.

Simulator mode

Without a serial port, or after simulator(True), the controller runs the same planner against a virtual arm and broadcasts its state. Everything works except the hardware: homing is instant, teleport() sets the pose, collisions are checked. Develop in the simulator and switch to the hardware with connect_hardware() or a restart with --serial.

The loop

The controller sends a packet to the board every 10 ms (100 Hz) and broadcasts status at 50 Hz. If the PC cannot keep up it logs loop overbudget by +N%, as a warning when it happens more than three times a minute (at DEBUG level otherwise); loop_stats() shows the figures. Lower PAROL6_CONTROL_RATE_HZ, close other programs, and keep logging at INFO or above: TRACE and DEBUG cost time.

Environment variables

Everything configurable without code, read at start-up:

Variable	Default
PAROL6_BLEND_HOLD_S	0.1
PAROL6_BUSY_THRESHOLD_MS	1.0
PAROL6_COLLISION_CHECK	1
PAROL6_COLLISION_CLEARANCE_M	0.005
PAROL6_COLLISION_JOG_LOOKAHEAD_S	0.15
PAROL6_COLLISION_PATH_SAMPLES	16
PAROL6_COLLISION_SRDF	computed
PAROL6_COM_FILE	computed
PAROL6_COM_PORT	—
PAROL6_CONTROL_RATE_HZ	100
PAROL6_EXECUTION_OVERRIDE_TRANSITION_S	1.0
PAROL6_MAX_BACKLOG_COUNT	500
PAROL6_MAX_BLEND_LOOKAHEAD	100
PAROL6_MCAST_GROUP	239.255.0.101
PAROL6_MCAST_IF	127.0.0.1
PAROL6_MCAST_PORT	50510
PAROL6_MCAST_TTL	1
PAROL6_PATH_SAMPLES	200
PAROL6_SERIAL	—
PAROL6_SETTLE_MAX_TICKS	20
PAROL6_STATUS_RATE_HZ	50
PAROL6_STATUS_STALE_S	0.5
PAROL6_STATUS_TRANSPORT	MULTICAST
PAROL6_STATUS_UNICAST_HOST	127.0.0.1
PAROL_TRACE	0

The ones you are most likely to touch: PAROL6_COM_PORT (the serial port), PAROL6_CONTROL_RATE_HZ and PAROL6_STATUS_RATE_HZ (the loop and broadcast rates), PAROL6_MCAST_GROUP and PAROL6_MCAST_PORT (where the status goes; PAROL6_STATUS_TRANSPORT=UNICAST with PAROL6_STATUS_UNICAST_HOST for networks without multicast), and PAROL6_COLLISION_CHECK (0 disables collision checking). A path or an expression as the default is marked computed: see config.py.

Security

The controller accepts any well-formed command on its UDP port from anyone who can reach it. That is by design, so that a GUI and a script can share it, and it means: run it on a trusted network, or bind --host 127.0.0.1.

Comments

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