Difference between revisions of "Multiwii Serial Protocol"

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A discussion on the MSP is in this thread: http://www.multiwii.com/forum/viewtopic.php?f=8&t=1516
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The general format of an MSP message is:
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<preamble>,<direction>,<size>,<command>,<data>,<crc>
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Where:
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preamble = the ASCII characters '$M'
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direction = the ASCII character '<' if to the MWC or '>' if from the MWC
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size = number of data bytes, binary. Can be zero as in the case of a data request to the MWC
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command = message_id as per the table below
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data = as per the table below. UINT16 values are LSB first.
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crc = XOR of <size>, <command> and each data byte into a zero'ed sum
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{| class="wikitable"
 
{| class="wikitable"
 
!command!!message_id!!direction!!data!!type!!comment
 
!command!!message_id!!direction!!data!!type!!comment
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!||||||||||
 
!||||||||||
 
|-
 
|-
−
||MSP_ATTITUDE||108||FC →||angx||INT 16||Range [-180;180]
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||MSP_ATTITUDE||108||FC →||angx||INT 16||Range [-1800;1800] (unit: 1/10 degree)
 
|-
 
|-
−
||||||||angy||INT 16||Range [-90;90]
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||||||||angy||INT 16||Range [-900;900] (unit: 1/10 degree)
 
|-
 
|-
 
||||||||heading||INT 16||Range [-180;180]
 
||||||||heading||INT 16||Range [-180;180]

Latest revision as of 11:21, 3 January 2015

A discussion on the MSP is in this thread: http://www.multiwii.com/forum/viewtopic.php?f=8&t=1516

The general format of an MSP message is:

<preamble>,<direction>,<size>,<command>,,<crc>

Where:

preamble = the ASCII characters '$M'

direction = the ASCII character '<' if to the MWC or '>' if from the MWC

size = number of data bytes, binary. Can be zero as in the case of a data request to the MWC

command = message_id as per the table below

data = as per the table below. UINT16 values are LSB first.

crc = XOR of <size>, <command> and each data byte into a zero'ed sum


command message_id direction data type comment
MSP_IDENT 100 FC → VERSION UINT 8 version of MultiWii
MULTITYPE UINT 8 type of multi:

TRI/QUADP,QUADX,BI,GIMBAL,Y6,HEX6,FLYING_WING,Y4,HEX6X,OCTOX8, OCTOFLATP,OCTOFLATX,AIRPLANE,HELI_120,HELI_90,VTAIL4,HEX6H,SINGLECOPTER,DUALCOPTER

MSP_VERSION UINT 8 not used currently
capability UINT 32 A 32 bit variable to indicate capability of FC board.

Currently, BIND button is used on first bit, DYNBAL on second, FLAP on third

MSP_STATUS 101 FC → cycleTime UINT 16 unit: microseconds
i2c_errors_count UINT 16
sensor UINT 16 BARO<<1|MAG<<2|GPS<<3|SONAR<<4
flag UINT 32 a bit variable to indicate which BOX are active, the bit position depends on the BOX which are configured
global_conf.currentSet UINT 8 to indicate the current configuration setting
MSP_RAW_IMU 102 FC → accx INT 16 unit: it depends on ACC sensor and is based on ACC_1G definition

MMA7455 64 / MMA8451Q 512 / ADXL345 265 / BMA180 255 / BMA020 63 / NUNCHUCK 200 / LIS3LV02 256 / LSM303DLx_ACC 256 / MPU6050 512 / LSM330 256

accy INT 16
accz INT 16
gyrx INT 16 unit: it depends on GYRO sensor.

For MPU6050, 1 unit = 1/4.096 deg/s

gyry INT 16
gyrz INT 16
magx INT 16 unit: it depends on MAG sensor.
magy INT 16
magz INT 16
MSP_SERVO 103 FC → Servo*8 16 x UINT 16 Range [1000;2000]

The servo order depends on multi type

MSP_MOTOR 104 FC → Motor*8 16 x UINT 16 Range [1000;2000]

The motor order depends on multi type

MSP_SET_MOTOR 214 → FC Motor*8 16 x UINT 16 use to set individual motor value (to be used only with DYNBALANCE config)
MSP_RC 105 FC → rcData[RC_CHANS] 16 x UINT 16 Range [1000;2000]

ROLL/PITCH/YAW/THROTTLE/AUX1/AUX2/AUX3AUX4

MSP_SET_RAW_RC 200 → FC rcData[RC_CHANS] 16 x UINT 16 Range [1000;2000]

ROLL/PITCH/YAW/THROTTLE/AUX1/AUX2/AUX3AUX4

This request is used to inject RC channel via MSP. Each chan overrides legacy RX as long as it is refreshed at least every second. See UART radio projects for more details.

MSP_RAW_GPS 106 FC → GPS_FIX UINT 8 0 or 1
GPS_numSat UINT 8
GPS_coord[LAT] UINT 32 1 / 10 000 000 deg
GPS_coord[LON] UINT 32 1 / 10 000 000 deg
GPS_altitude UINT 16 meter
GPS_speed UINT 16 cm/s
GPS_ground_course UINT 16 unit: degree*10
MSP_SET_RAW_GPS 201 → FC GPS_FIX UINT 8 this request is used to inject GPS data (annex GPS device or simulation purpose)
GPS_numSat UINT 8
GPS_coord[LAT] UINT 32 1 / 10 000 000 deg
GPS_coord[LON] UINT 32 1 / 10 000 000 deg
GPS_altitude UINT 16 meter
GPS_speed UINT 16 cm/s
MSP_COMP_GPS 107 FC → GPS_distanceToHome UINT 16 unit: meter
GPS_directionToHome UINT 16 unit: degree (range [-180;+180])
GPS_update UINT 8 a flag to indicate when a new GPS frame is received (the GPS fix is not dependent of this)
MSP_ATTITUDE 108 FC → angx INT 16 Range [-1800;1800] (unit: 1/10 degree)
angy INT 16 Range [-900;900] (unit: 1/10 degree)
heading INT 16 Range [-180;180]
MSP_ALTITUDE 109 FC → EstAlt INT 32 cm
vario INT 16 cm/s
MSP_ANALOG 110 FC → vbat UINT 8 unit: 1/10 volt
intPowerMeterSum UINT 16
rssi UINT 16 range: [0;1023]
amperage UINT 16
MSP_RC_TUNING 111 FC → byteRC_RATE UINT 8 range [0;100]
byteRC_EXPO UINT 8 range [0;100]
byteRollPitchRate UINT 8 range [0;100]
byteYawRate UINT 8 range [0;100]
byteDynThrPID UINT 8 range [0;100]
byteThrottle_MID UINT 8 range [0;100]
byteThrottle_EXPO UINT 8 range [0;100]
MSP_SET_RC_TUNING 204 → FC byteRC_RATE UINT 8
byteRC_EXPO UINT 8
byteRollPitchRate UINT 8
byteYawRate UINT 8
byteDynThrPID UINT 8
byteThrottle_MID UINT 8
byteThrottle_EXPO UINT 8
MSP_PID 112 FC → PIDITEMS x conf.pid[] 3*PIDITEMS x UINT 8 Currently, PIDITEMS is constant = 10

Order : ROLL / PITCH / YAW / ALT / POS / POSR / NAVR / LEVEL /MAG / VEL VEL is not used

MSP_SET_PID 202 → FC PIDITEMS x conf.pid[] 3*PIDITEMS x UINT 8
MSP_BOX 113 FC → BOXITEMS x conf.activate[] BOXITEMS x UINT 16 BOXITEMS number is dependant of multiwii configuration

The size of the message is enough to know the number of BOX For each BOX, there is a 16 bit variable which indicates the AUX1->AUX4 activation switch. Bit 1: AUX1 LOW state / bit 2: AUX1 MID state / bit 3: AUX1 HIGH state / bit 4: AUX2 LOW state ….. bit 13: AUX 4 HIGH state

MSP_SET_BOX 203 → FC BOXITEMS x conf.activate[] BOXITEMS x UINT 16
MSP_MISC 114 FC → intPowerTrigger1 UNIT 16
conf.minthrottle UNIT 16 minimum throttle to run motor in idle state ( range [1000;2000] )
MAXTHROTTLE UNIT 16 maximum throttle ( range [1000;2000] )
MINCOMMAND UNIT 16 throttle at the lowest position ( range [1000;2000] , could be occasionally a little bit less than 1000 depending on ESCs)
conf.failsafe_throttle UNIT 16 should be set less than hover state ( range [1000;2000] )
plog.arm UNIT 16 counter
plog.lifetime UNIT 32
conf.mag_declination UNIT 16 magnetic declination ( unit:1/10 degree )
conf.vbatscale UNIT 8
conf.vbatlevel_warn1 UNIT 8 unit: 1/10 volt
conf.vbatlevel_warn2 UNIT 8 unit: 1/10 volt
conf.vbatlevel_crit UNIT 8 unit: 1/10 volt
MSP_SET_MISC 207 → FC intPowerTrigger1 UNIT 16
conf.minthrottle UNIT 16
MAXTHROTTLE UNIT 16 not used currently as a set variable
MINCOMMAND UNIT 16 not used currently as a set variable
conf.failsafe_throttle UNIT 16
plog.arm UNIT 16 not used, it's here to have the same struct as get
plog.lifetime UNIT 32 not used, it's here to have the same struct as get
conf.mag_declination UNIT 16 magnetic declination ( unit:1/10 degree )
conf.vbatscale UNIT 8
conf.vbatlevel_warn1 UNIT 8 unit: 1/10 volt
conf.vbatlevel_warn2 UNIT 8 unit: 1/10 volt
conf.vbatlevel_crit UNIT 8 unit: 1/10 volt
MSP_MOTOR_PINS 115 FC → 8*PWM_PIN 8 x UNIT 8 motor pin indication
MSP_BOXNAMES 116 FC → string of BOX items string all the configured CHECKBOX name separated by ;
MSP_PIDNAMES 117 FC → string of PID items string all the PID name separated by ;
MSP_WP 118 FC → wp_no UINT 8 not fully implemented yet, works partially for HOME POSITION (wp 0) and HOLD position (wp 15)
lat UINT 32
lon UINT 32
AltHold UINT 32
heading UINT 16
time to stay UINT 16
nav flag UINT 8
MSP_SET_WP 209 → FC wp_no UINT 8
lat UINT 32
lon UINT 32
AltHold UINT 32
heading UINT 16
time to stay UINT 16
nav flag UINT 8
MSP_BOXIDS 119 FC → ID*CHECKBOXITEMS CHECKBOXITEMS x UINT 8 each BOX (used or not) have a unique ID.

In order to retrieve the number of BOX and which BOX are in used, this request can be used. It is more efficient than retrieving BOX names if you know what BOX function is behing the ID. See enum MultiWii.cpp (0: ARM, 1 ANGLE, 2 HORIZON, …)

MSP_SERVO_CONF 120 FC → 8 x conf.servoConf[] 8 x [UINT 16, UINT 16, UINT 16, UINT 8] struct servo_conf_ is 7 bytes length: min:2 / max:2 / middle:2 / rate:1

[1000;2000], [1000;2000], [1000;2000], [0;100] Special use: middle normal range is [1000;2000] If middle < RC_CHANS => the relevant rc channel is the middle position of the servo (usefull for gimbal where you wnt to control the middle axis via a rc chan)

Depending on the servo use in multiwii type, rate is used to reverse the direction of servo (first bit) or to set a proportional range

MSP_SET_SERVO_CONF 212 → FC 8 x conf.servoConf[] 8 x [UINT 16, UINT 16, UINT 16, UINT 8]
MSP_ACC_CALIBRATION 205 → FC no param used to calibrate the ACC
MSP_MAG_CALIBRATION 206 → FC no param used to calibrate the MAG
MSP_RESET_CONF 208 → FC no param reset all params to default
MSP_SELECT_SETTING 210 → FC global_conf.currentSet UINT 8 select the setting configuration (you can set for instance different pid and rate)

Range: 0, 1 or 2

MSP_SET_HEAD 211 → FC magHold INT 16 Set a new head lock reference

Range [-180;+180]

MSP_BIND 240 → FC no param Currently only uses to bind spektrum sttellites
MSP_EEPROM_WRITE 250 → FC no param write the settings to the eeprom
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