Robot Mower Communications Standard

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Robot Mower Communications Standard (RMCS) DRAFT

Describes message format used to externally control a robot mower (e.g. Ardumower-based) using a serial line (PC/Raspberry/Android etc.)


  • add robot setup commands


  • Serial interface (or serial USB)
  • ...

Message format

NMEA 0183 compatible format (ASCII encoded)

message structure: $IDMSG,data,*XX<cr><lf>

message components:

  • $: start of message symbol
  • ID: device ID (the destination of a command message or source of an event message) - examples: RM (robot mower), DW (ranging beacons), ...
  • MSG: message type (see below)
  • data: comma separated message data (see below) - if a value is not existing it should be empty
  • XX: checksum: representation of two hexadecimal characters of an XOR of all characters in the sentence between – but not including – the $ and the * character.
  • <cr><lf>: end of message symbol

example: $RMSTA,145984,1,,,179.8,,,0,0*3F<cr><lf>


There are command and event messages. Command messages are received by the robot, event messages are sent by the robot.


  • $RMREQ: Request an event or configure message event command (frequency, one-time events etc.)
  • $RMTRG: Configure a sensor trigger
  • $RMMOW: Set mowing state command (start mowing, stop mowing, go to docking station)
  • $RMMOV: Move robot until sensor trigger command
  • $RMKOA: Keep ongoing action command (mower communications saftety)


  • $RMSTA: Robot state event (robot state, errors, battery, charger)
  • $RMCFG: Robot mower configuration event (protocol version, available sensors)
  • $RMMOT: motor current sensor event
  • $RMSON: ultrasonic sensor event
  • $RMBUM: bumper sensor event
  • $RMODO: odometry event
  • $RMGPS: GPS event
  • $RMPER: perimeter sensor event
  • $RMDRO: drop sensor event
  • $RMIMU: IMU event
  • $RMBEA: beacons ranging data event (e.g. DW1000)

Command: Request or onfigure a message event (frequency, one-time events)

This command is used to configure the frequency for an event message or to request a certain message once.


  • MSG: the message type (CFG, STA, TRG, MOT, SON, BUM etc.)
  • f: frequency (0 - 10.0 Hz), 0 means turn off periodic events for this message, -1 means fire message once
  • t: enable trigger for this message (0/1)

Command: Set mowing state (start,stop,dock)

This command is used to for remote controlling the mower actions.


  • s: stop mowing (0), start mowing (1), go to docking station (2)

Command: Move robot until sensor trigger

This command is used to control the robot movements directly. Once a sensor triggers (bumper, perimeter, etc.), the robot should stop.


  • m: mowing motor on (1) or off (0)
  • l: left motor target rpm
  • r: right motor target rpm
  • p: PID_Kp
  • i: PID_Ki
  • d: PID_Kd

Command: Keep ongoing action (mower communications saftety)

This command is used to control the robot movements directly. The mower will stop motors if not receiving another message within 2 seconds.


Event: Robot state (robot state, errors, battery, charger)

Robot will send current state via this message.


  • ts: timestamp ms
  • s: robot state: stopped (0), mowing (1), busy (2), error (3), going to dock (4)
  • o: docking state: not docked (0), docked (1)
  • e: error code
  • b: battery percent
  • bl: battery low (0/1)
  • c: charging percent
  • h: absolute compass heading in degree
  • d: moved distance in meter since last message

Event: Robot mower configuration (protocol version, type of sensors)

Robot will send a summary of the robot's configuration via this message.


  • p: robot is using protocol version (currently 1)
  • m: robot requires minimum protocol version (currently 1)
  • d: Docking station available (1/0)
  • pfl: perimeterFrontLeft available (1/0)
  • pfr: perimeterFrontRight available (1/0)
  • pfc: perimeterFrontCenter available (1/0)
  • prl: perimeterRearLeft available (1/0)
  • prr: perimeterRearRight available (1/0)
  • prc: perimeterRearCenter available (1/0)
  • ih: IMU compass available (1/0)
  • ip: IMU pitch/roll available (1/0)
  • o: Odometry available (1/0)
  • g: GPS available (1/0)
  • ul: ultrasonicLeft available (1/0)
  • ur: ultrasonicRight available (1/0)
  • uc: ultrasonicCenter available (1/0)
  • dl: dropSensorLeft available (1/0)
  • dr: dropSensorRight available (1/0)

Event: motor current sensor data

$RMMOT,ts, ml, mr, mm, mlt, mrt, mmt

  • ts: timestamp ms
  • ml: left motor current (Ampere)
  • mr: right motor current (Ampere)
  • mm: mower motor current (Ampere)
  • mlt: left motor stall triggered (0/1)
  • mrt: left motor stall triggered (0/1)
  • mmt: mower motor stall triggered (0/1)

Event: ultrasonic sensor data


  • ts: timestamp ms
  • ul: ultrasonicLeft meter
  • ur: ultrasonicRight meter
  • uc: ultrasonicCenter meter
  • ult: ultrasonicLeft triggered (0/1)
  • urt: ultrasonicRight triggered (0/1)
  • uct: ultrasonicCenter triggered (0/1)

Event: bumper sensor data


  • ts: timestamp ms
  • bl: bumperLeft value
  • br: bumperRight value
  • bc: bumperCenter value
  • blt: bumperLeft triggered (0/1)
  • brt: bumperRight triggered (0/1)
  • bct: bumperCenter triggered (0/1)

Event: odometry data

$RMODO,ts, ol, or

  • ts: timestamp ms
  • ol: left odometry
  • or: right odometry

Event: GPS data

$RMGPS,ts, ga, go

  • ts: timestamp ms
  • ga: GPSlatitude
  • go: GPSlongitude

Event: perimeter sensor data


  • ts: timestamp ms
  • pfl: perimeterFrontLeft value
  • pfr: perimeterFrontRight value
  • pfc: perimeterFrontCenter value
  • prl: perimeterRearLeft value
  • prr: perimeterRearRight value
  • prc: perimeterRearCenter value
  • pflt: perimeterFrontLeft triggered (0/1)
  • pfrt: perimeterFrontRight triggered (0/1)
  • pfct: perimeterFrontCenter triggered (0/1)
  • prlt: perimeterRearLeft triggered (0/1)
  • prrt: perimeterRearRight triggered (0/1)
  • prct: perimeterRearCenter triggered (0/1)

Event: drop sensor data


  • ts: timestamp ms
  • dl: left drop sensor value (0/1)
  • dr: right drop sensor value (0/1)
  • dlt: left drop sensor triggered (0/1)
  • drt: right drop sensor triggered (0/1)

Event: IMU data


  • ts: timestamp ms
  • ih: IMUcompassHeading degree
  • ip: IMUpitch degree
  • ir: IMUroll degree
  • tr: tilt triggered (0/1)

Event: beacon ranging data (e.g. DW1000)


  • t: timestamp ms
  • b1,b2,b3,b4,...: beacons ranging in meter

Proprietary messages

  • Any proprietary message types not defined by this protocol