Abstract

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.)

TODO:

add sensor trigger events
add robot setup commands

Requirements

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>

Messages

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

commands:

$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)

events:

$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.

$RMREQ,MSG,f,t<cr><lf>

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.

$RMMOW,s<cr><lf>

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.

$RMMOV,m,l,r,p,i,d<cr><lf>

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.

$RMKOA<cr><lf>

Robot state event (robot state, errors, battery, charger)

Robot will send current state via this message.

$RMSTA,ts,s,e,b,bl,c,h,d<cr><lf>

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

Robot mower configuration event (protocol version, type of sensors)

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

$RMCFG,p,m,d,pfl,pfr,pfc,prl,prr,prc,ih,ip,o,g,ul,ur,uc,dl,dr<cr><lf>

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)

motor current sensor data event

$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)

ultrasonic sensor data event

$RMSON,ts,ul,ur,uc,ult,urt,uct

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)

bumper sensor data event

$RMBUM,ts,bl,br,bc,blt,brt,bct

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)

odometry data event

$RMODO,ts, ol, or

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

GPS data event

$RMGPS,ts, ga, go

ts: timestamp ms
ga: GPSlatitude
go: GPSlongitude

perimeter sensor data event

$RMPER,ts,pfl,pfr,pfc,prl,prr,prc,pflr,pfrt,pfct,prlt,prrt,prct

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)

drop sensor data event

$RMDRO,ts,dl,dr,dlt,drt

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)

IMU data event

$RMIMU,ts,ih,ip,ir,tr

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

beacon ranging data event (e.g. DW1000)

$RMBEA,t,b1,b2,b3,b4,...<cr><lf>

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

Proprietary

Any proprietary message types not defined by this protocol

Robot Mower Communications Standard

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