NMEA 0183 (ASCII) Protocol

For simple use, the Inertial Sense device supports a human-readable NMEA communications protocol based on NMEA 0183. The NMEA protocol is human readable from in a command line terminal but is less optimal than the binary protocol in terms of message length for the same amount of data.

Communications Examples

The NMEA Communications Example Project demonstrates how to implement the protocol.

Packet Structure

The Inertial Sense NMEA protocol follows the standard NMEA 0183 message structure:

• 1 byte – Start packet, $ (0x24)
• n bytes – packet identifier
• 1 byte – comma (0x2C)
• n bytes – comma separated list of data, can include decimals and text
• 1 byte – checksum marker, * (0x2A)
• 2 bytes – checksum in hex format (i.e. f5 or 0a), 0 padded and lowercase
• 2 bytes – End packet, \r\n (0x0D, 0x0A)

The packet checksum is an 8 bit integer and is calculated by calculating the exclusive OR of all bytes in between and not including the $ and * bytes. The packet checksum byte is converted to a 2 byte NMEA hex code, and left padded with 0 if necessary to ensure that it is always 2 bytes. The checksum is always lowercase hexadecimal characters. See NMEA 0183 message structure for more details. The NMEA string checksum is automatically computed and appended to string when using the InertialSense SDK serialPortWriteAscii function or can be generated using an online checksum calculator. For example: MTK NMEA checksum calculator

Persistent Messages

The persistent messages option saves the current data stream configuration to flash memory for use following reboot, eliminating the need to re-enable messages following a reset or power cycle.

• To save current NMEA persistent messages - send the $PERS command.
• To disable persistent messages - send the $STPB](#stpb) followed by [$PERS.

Binary persistent messages are also available.

Enabling Persistent Messages - EvalTool

To enable persistent NMEA messages using the EvalTool:

• Enable the desired NMEA messages in the EvalTool "Data Sets" tab. Select DID_NMEA_BCAST_PERIOD in the DID menu and set the desired NMEA messages period to a non-zero value.
• Press the "Save Persistent" button in the EvalTool "Data Logs" tab to store the current message configuration to flash memory.
• Reset the IMX and verify the messages are automatically streaming. You can use a generic serial port program like putty or the EvalTool->Data Logs->Data Log->Messages dialog to view the NMEA messages.

To disable all persistent messages using the EvalTool, click the "Stop Streaming" button and then "Save Persistent" button.

NMEA Input Messages

The following NMEA messages can be received by the IMX.

Message	Description
$ASCB*13\r\n	Query the broadcast rate of NMEA output messages.
ASCB	Set the broadcast period of NMEA output messages. (Outdated. Use ASCE instead.)
ASCE	Set the broadcast period of selected NMEA output messages.
$INFO*0E\r\n	Query device information.
$SRST*06\r\n	Software reset.
$PERS*14\r\n	Save persistent messages to flash.
$STPB*15\r\n	Stop broadcast of all messages (NMEA and binary) on all ports.
$STPC*14\r\n	Stop broadcast of all messages (NMEA and binary) on current port.

ASCB

(ASCB is outdated and ASCE is recommended for use instead.)
Enable NMEA message and set broadcast periods. The period is in milliseconds with no thousands separator character. “xx” is the two-character checksum. Each field can be left blank in which case the existing broadcast period for that field is not modified, or 0 to disable streaming. Actual broadcast period for each message is configurable as a period multiple of the Data Source Update Rates

$ASCB,options,d,d,d,d,d,d,d,d,d,d,d,d,d,d,d*xx\r\n

Index	Field	Description
1	options	Port selection. Combine by adding options together: 0=current, 1=ser0, 2=ser1, 4=ser2, 8=USB, 512=persistent (remember after reset)
2	PIMU	Broadcast period multiple for PIMU IMU message.
3	PPIMU	Broadcast period multiple for PPIMU preintegrated IMU message.
4	PINS1	Broadcast period multiple for PINS1 INS output (euler, NED) message.
5	PINS2	Broadcast period multiple for PINS2 INS output (quaternion, LLA) message.
6	PGPSP	Broadcast period multiple for PGPSP GPS position message.
7	PRIMU	Broadcast period multiple for PRIMU Raw IMU message.
8	GGA	Broadcast period multiple for NMEA standard GGA (fix, 3D location, and accuracy) message.
9	GLL	Broadcast period multiple for NMEA standard GLL (2D location and time) message.
10	GSA	Broadcast period multiple for NMEA standard GSA (DOP and active satellites) message.
11	RMC	Broadcast period multiple for NMEA standard RMC (minimum specific GPS/Transit) message.
12	ZDA	Broadcast period multiple for NMEA standard ZDA (UTC Time/Date) message.
13	PASHR	Broadcast period multiple for NMEA standard PASHR (euler) message.
14	GxGSV	Broadcast period multiple for NMEA standard GSV satellite info (all active constellations sent with corresponding talker IDs).
15	VTG	Broadcast period multiple for NMEA standard VTG track made good and speed over ground.

ASCE

Enable NMEA message output streaming by specifying the NMEA message ID and broadcast period. The period is the multiple of the data source period (i.e. a GNSS message with period multiple of 2 and data source period of 200 ms (5 Hz) will broadcast every 400 ms). “xx” is the two-character checksum. A period of 0 will disable message streaming. The broadcast period for each message is configurable as a period multiple of the Data Source Update Rates. Up to twenty different NMEA messages can be enabled by repeating the message ID and period sequence within an ASCE message.

$ASCE,options,(id,period)*xx\r\n

Index	Field	Description
1	options	Port selection. Combine by adding options together: 0=current, 1=ser0, 2=ser1, 4=ser2, 8=USB, 512=persistent (remember after reset)
		Start of repeated group (1...20 times)
2+n*2	ID	NMEA message ID to be streamed. See the message ID in the NMEA output messages table.
3+n*2	period	Broadcast period multiple for specified message. Zero disables streaming.
		End of repeated group (1...20 times)

Example Messages

The following examples NMEA messages enable IMX data streaming output. The data period is 1, full data source rates, for those that do not specify the output rate.

Message	Data (Output Rate)**
$ASCE,0,6,1,7,1,8,1,10,1,14,1*04\r\n	GGA, GLL, GSA, ZDA, GSV (all at 5Hz)
$ASCE,0,5,2,2,1,7,1*0A\r\n	PINS2 (31.25 Hz), PPIMU (62.5Hz), GGA (5Hz)
$ASCE,0,0,1*09\r\n	PIMU
$ASCE,0,1,1*08\r\n	PPIMU
$ASCE,0,2,1*0B\r\n	PRIMU
$ASCE,0,3,1*0A\r\n	PINS1
$ASCE,0,4,1*0D\r\n	PINS2
$ASCE,0,5,1*0C\r\n	PGPSP
$ASCE,0,6,1*0F\r\n	GGA
$ASCE,0,7,1*0E\r\n	GLL
$ASCE,0,8,1*01\r\n	GSA
$ASCE,0,9,1*00\r\n	RMC
$ASCE,0,10,1*38\r\n	ZDA
$ASCE,0,11,1*39\r\n	PASHR
$ASCE,0,12,1*3A\r\n	PSTRB
$ASCE,0,13,1*3B\r\n	INFO
$ASCE,0,14,1*3C\r\n	GSV
$ASCE,0,15,1*3D\r\n	VTG

^** These rates assume the default settings for data source rates.

PERS

Send this command to save current persistent messages to flash memory for use following reboot. This eliminates the need to re-enable messages following a reset or power cycle. In order to disable persistent messages, all messages must be disabled and then the 'save persistent messages' command should be sent.

$PERS*14\r\n

STPB

Stop all broadcasts (both binary and NMEA) on all ports by sending the following packet:

$STPB*15\r\n

The hexadecimal equivalent is:

24 53 54 50 42 2A 31 35 0D 0A

STPC

Stop all broadcasts (both binary and NMEA) on the current port by sending the following packet:

$STPC*14\r\n

The hexadecimal equivalent is:

24 53 54 50 43 2A 31 34 0D 0A

NMEA Output Messages

The following NMEA messages can be sent by the IMX. The message ID is used with the $ASCE message to enable message streaming.

Message	ID	Description
ASCB		Broadcast period of NMEA output messages.
PIMU	0	IMU data (3-axis gyros and accelerometers) in the body frame.
PPIMU	1	Preintegrated IMU: delta theta (rad) and delta velocity (m/s).
PRIMU	2	Raw IMU data (3-axis gyros and accelerometers) in the body frame.
PINS1	3	INS output: euler rotation w/ respect to NED, NED position from reference LLA.
PINS2	4	INS output: quaternion rotation w/ respect to NED, ellipsoid altitude.
PGPSP	5	GPS position data.
GGA	6	Standard NMEA GGA GPS 3D location, fix, and accuracy.
GLL	7	Standard NMEA GLL GPS 2D location and time.
GSA	8	Standard NMEA GSA GPS DOP and active satellites.
RMC	9	Standard NMEA RMC Recommended minimum specific GPS/Transit data.
ZDA	10	Standard NMEA ZDA UTC Time/Date message.
PASHR	11	Standard NMEA PASHR (euler) message.
PSTRB	12	Strobe event input time.
INFO	13	Device information.
GSV	14	Standard NMEA GSV satellite info (all active constellations sent with corresponding talker IDs).
VTG	15	Standard NMEA VTG track made good and speed over ground.

The field codes used in the message descriptions are: lf = double, f = float, d = int.

PIMU

IMU sensor data (3-axis gyros and accelerometers) in the body frame.

$PIMU,lf,f,f,f,f,f,f*xx\r\n
       1 2 3 4 5 6 7

Index	Field	Units	Description
1	time	sec	Time since system power up
3	IMU pqr[0]	rad/sec	IMU angular rate gyro – X
2	IMU pqr[1]	rad/sec	IMU angular rate gyro – Y
4	IMU pqr[2]	rad/sec	IMU angular rate gyro – Z
5	IMU acc[0]	m/s2	IMU linear acceleration – X
6	IMU acc[1]	m/s2	IMU linear acceleration – Y
7	IMU acc[2]	m/s2	IMU linear acceleration – Z

PPIMU

Preintegrated inertial measurement unit (IMU) sensor data, delta theta in radians and delta velocity in m/s in the body frame. Also known as coning and sculling integrals.

$PPIMU,lf,f,f,f,f,f,f,f*xx\r\n
        1 2 3 4 5 6 7 8

Index	Field	Units	Description
1	time	sec	Time since system power up
2	theta[0]	rad	IMU delta theta integral – X
3	theta[1]	rad	IMU delta theta integral – Y
4	theta[2]	rad	IMU delta theta integral – Z
8	vel[0]	m/s	IMU delta velocity integral – X
9	vel[1]	m/s	IMU delta velocity integral – Y
10	vel[2]	m/s	IMU delta velocity integral – Z
14	dt	s	Integration period for delta theta vel

PRIMU

Raw IMU sensor data (3-axis gyros and accelerometers) in the body frame (up to 1KHz). Use this IMU data for output data rates faster than DID_FLASH_CONFIG.startupNavDtMs. Otherwise we recommend use of PIMU or PPIMU as they are oversampled and contain less noise. 0 to disable.

$PRIMU,lf,f,f,f,f,f,f*xx\r\n
        1 2 3 4 5 6 7

Index	Field	Units	Description
1	time	sec	Time since system power up
3	Raw IMU pqr[0]	rad/sec	Raw IMU angular rate gyro – X
2	Raw IMU pqr[1]	rad/sec	Raw IMU angular rate gyro – Y
4	Raw IMU pqr[2]	rad/sec	Raw IMU angular rate gyro – Z
5	Raw IMU acc[0]	m/s2	Raw IMU linear acceleration – X
6	Raw IMU acc[1]	m/s2	Raw IMU linear acceleration – Y
7	Raw IMU acc[2]	m/s2	Raw IMU linear acceleration – Z

PINS1

INS output with Euler angles and NED offset from the reference LLA.

$PINS1,lf,d,d,d,f,f,f,f,f,f,lf,lf,lf,f,f,f*xx\r\n
        1 2 3 4 5 6 7 8 9 0  1  2  3 4 5 6

Index	Field	Units	Description
1	timeOfWeek	sec	Seconds since Sunday morning in GMT
2	GPS week	weeks	Number of weeks since January 1st of 1980 in GMT
3	insStatus		INS Status Flags
4	hdwStatus		Hardware Status Flags
5	theta[0]	rad	Euler angle – roll
6	theta[1]	rad	Euler angle – pitch
7	theta[2]	rad	Euler angle – yaw
8	UVW[0]	m/s	Velocity in body frame – X
9	UVW[1]	m/s	Velocity in body frame – Y
10	UVW[2]	m/s	Velocity in body frame – Z
11	Latitude	deg	WGS84 Latitude
12	Longitude	deg	WGS84 Longitude
13	HAE Altitude	m	Height above ellipsoid (vertical elevation)
14	NED[0]	m	Offset from reference LLA – North
15	NED[1]	m	Offset from reference LLA – East
16	NED[2]	m	Offset from reference LLA – Down

PINS2

INS output with quaternion attitude.

$PINS2,lf,d,d,d,f,f,f,f,f,f,f,lf,lf,lf*xx\r\n
        1 2 3 4 5 6 7 8 9 0 1  2  3  4

Index	Field	Units	Description
1	timeOfWeek	sec	Seconds since Sunday morning in GMT
2	GPS week	weeks	Number of weeks since January 1st of 1980 in GMT
3	insStatus		INS Status Flags
4	hdwStatus		Hardware Status Flags
5	qn2b[0]		Quaternion rotation (NED to body) – W
6	qn2b[1]		Quaternion rotation (NED to body) – X
7	qn2b[2]		Quaternion rotation (NED to body) – Y
8	qn2b[3]		Quaternion rotation (NED to body) – Z
9	UVW[0]	m/s	Velocity in body frame – X
10	UVW[1]	m/s	Velocity in body frame – Y
11	UVW[2]	m/s	Velocity in body frame – Z
12	Latitude	deg	WGS84 Latitude
13	Longitude	deg	WGS84 Longitude
14	HAE altitude	m	Height above ellipsoid (vertical elevation)

PGPSP

GPS navigation data.

$PGPSP,d,d,d,lf,lf,lf,f,f,f,f,f,f,f,f,f,f*xx\r\n
       1 2 3  4  5  6 7 8 9 0 1 2 3 4 5 6

$PGPSP,337272200,2031,1075643160,40.33057800,-111.72581630,1406.39,1425.18,0.95,0.37,0.55,-0.02,0.02,-0.03,0.17,39.5,337182.4521*4d\r\n

Index	Field	Units	Description
1	timeOfWeekMs	ms	GPS time of week in milliseconds since Sunday morning in GMT
2	GPS week	weeks	GPS number of weeks since January 1st of 1980 in GMT
3	status		(see eGpsStatus) GPS status: [0x000000xx] number of satellites used, [0x0000xx00] fix type, [0x00xx0000] status flags
4	Latitude	deg	WGS84 Latitude
5	Longitude	deg	WGS84 Longitude
6	HAE altitude	m	Height above WGS84 ellipsoid
7	MSL altitude	m	Elevation above mean sea level
8	pDOP	m	Position dilution of precision
9	hAcc	m	Horizontal accuracy
10	vAcc	m	Vertical accuracy
11	Velocity X	m/s	ECEF X velocity
12	Velocity Y	m/s	ECEF Y velocity
13	Velocity Z	m/s	ECEF Z velocity
14	sAcc	m/s	Speed accuracy
15	cnoMean	dBHz	Average of all satellite carrier to noise ratios (signal strengths) that non-zero
16	towOffset	s	Time sync offset between local time since boot up to GPS time of week in seconds. Add this to IMU and sensor time to get GPS time of week in seconds.
17	leapS	s	GPS leap second (GPS-UTC) offset. Receiver's best knowledge of the leap seconds offset from UTC to GPS time. Subtract from GPS time of week to get UTC time of week.

GGA

NMEA GPS fix, 3D location and accuracy data.

$GPGGA,204153.200,4003.34331,N,11139.51872,W,1,25,0.93,1433.997,M,18.82,M,,*6d\r\n
                1          2 3           4 5 6  7    8     9    0     1 2 3 4

Index	Field	Units	Description	Example
1	HHMMSS.sss		UTC time (fix taken at 20:41:53.200 UTC)	204153.200
2,3	Latitude	deg,min	WGS84 latitude (DDmm.mmmmm,N)	4003.34331,N
4,5	Longitude	deg,min	WGS84 longitude (DDDmm.mmmmm,E)	11139.51872,W
6	Fix quality		0 = invalid, 1 = GPS fix (SPS), 2 = DGPS fix, 3 = PPS fix, 4 = RTK Fix, 5 = RTK Float, 6 = estimated (dead reckoning), 7 = Manual input mode, 8 = Simulation mode	1
7	# Satellites		Number of satellites in use	15
8	hDop	m	Horizontal dilution of precision	0.9
9,10	MSL_altitude	m	Elevation above mean sea level (MSL)	545.4,M
11,12	Undulation	m	Undulation of geoid. Height of the geoid above the WGS84 ellipsoid.	46.9,M
13	empty	s	Time since last DGPS update
14	empty		DGPS station ID number

GLL

NMEA geographic position, latitude / longitude and time.

$GPGLL,4916.45123,N,12311.12324,W,225444.800,A*33\r\n
                1 2           3 4          5 6

Index	Field	Units	Description	Example
1,2	Latitude	deg,min	WGS84 latitude (DDmm.mmmmm,N)	4916.45123,N
3,4	Longitude	deg,min	WGS84 longitude (DDDmm.mmmmm,E)	12311.12324,W
5	HHMMSS.sss		UTC time (fix taken at 22:54:44.8 UTC)	225444.800
6	Valid		Data valid (A=active, V=void)	A

GSA

NMEA GPS DOP and active satellites.

$GPGSA,A,3,04,05,,09,12,,,24,,,,,2.5,1.3,2.1*39\r\n
       1 2  3  4 ...              15  16  17

Index	Field	Units	Description	Example
1			Auto selection of 2D or 3D fix (M = manual)	A
2	Fix quality		Fix quality (1 = none, 2 = 2D, 3 = 3D)	3
3-14	Sat ID		Satellite ID (PRNs)	04,05,,09,12,,,24,,,,,
15	pDop	m	Dilution of precision	2.5
16	hDop	m	Horizontal dilution of precision	1.3
17	vDop	m	Vertical dilution of precision	2.1

RMC

NMEA GPS recommended minimum specific GPS/Transit data.

eg1. $GPRMC,081836,A,3751.65,S,14507.36,E,000.0,360.0,130998,011.3,E*62\r\n
eg2. $GPRMC,225446,A,4916.45,N,12311.12,W,000.5,054.7,191194,020.3,E*68\r\n

           225446       Time of fix 22:54:46 UTC
           A            Navigation receiver warning A = OK, V = warning
           4916.45,N    Latitude 49 deg. 16.45 min North
           12311.12,W   Longitude 123 deg. 11.12 min West
           000.5        Speed over ground, Knots
           054.7        Course Made Good, True
           191194       Date of fix  19 November 1994
           020.3,E      Magnetic variation 20.3 deg East
           *68          mandatory checksum

eg3. $GPRMC,220516,A,5133.82,N,00042.24,W,173.8,231.8,130694,004.2,W*70\r\n
              1    2    3    4    5     6    7    8      9     10  11 12

      1   220516     Time Stamp
      2   A          validity - A-ok, V-invalid
      3   5133.82    current Latitude
      4   N          North/South
      5   00042.24   current Longitude
      6   W          East/West
      7   173.8      Speed in knots
      8   231.8      True course
      9   130694     Date Stamp
      10  004.2      Variation
      11  W          East/West
      12  *70        checksum

eg4. $GPRMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,ddmmyy,x.x,a*hh\r\n
1    = UTC of position fix
2    = Data status (V=navigation receiver warning)
3    = Latitude of fix
4    = N or S
5    = Longitude of fix
6    = E or W
7    = Speed over ground in knots
8    = Track made good in degrees True
9    = UT date
10   = Magnetic variation degrees (Easterly var. subtracts from true course)
11   = E or W
12   = Checksum

VTG

NMEA GPS track made good and speed over ground.

eg1. $GPVTG,140.88,T,,M,8.04,N,14.89,K,D*05\r\n

0   Message ID $GPVTG
1   Track made good (degrees true)
2   T: track made good is relative to true north
3   Track made good (degrees magnetic)
4   M: track made good is relative to magnetic north
5   Speed, in knots
6   N: speed is measured in knots
7   Speed over ground in kilometers/hour (kph)
8   K: speed over ground is measured in kph
9   Mode indicator:
        A: Autonomous mode
        D: Differential mode
        E: Estimated (dead reckoning) mode
        M: Manual Input mode
        S: Simulator mode
        N: Data not valid
10  The checksum data, always begins with *

ZDA

NMEA GPS UTC Time and Date specification.

$GPZDA,213301.200,31,08,2023,00,00*41\r\n
                1  2  3    4  5  6

Index	Field	Units	Description	Example
1	HHMMSS.sss		UTC Time	213301.200
2	Day		Day	31
3	Month		Month	08
4	Year		Year	2023
5	localHrs		Local time zone hours	00
6	localMin		Local time zone minutes	00

GSV

NMEA GNSS satellites in view. xx corresponds to a constellation talker ID, shown in the table below.

Contains the number of sats in view, PRN numbers, elevation, azimuth and SNR value. Each message includes up to four satellites. When there are more than 4 sats for a constellation, multiple messages are sent. The total number of messages and the message number are included in each message.

Example:

$GPGSV,6,1,23,02,40,310,43,08,07,324,31,10,48,267,45,15,37,053,45*7C\r\n
$GPGSV,6,2,23,16,12,268,35,18,69,078,41,23,74,336,40,24,15,111,37*79\r\n
$GPGSV,6,3,23,26,02,239,31,27,35,307,38,29,12,162,37,32,14,199,39*7B\r\n
$GPGSV,6,4,23,44,43,188,43,46,40,206,43,522,48,267,45,527,37,053,26*73\r\n
$GPGSV,6,5,23,530,69,078,34,535,74,336,34,536,15,111,25,538,02,239,18*74\r\n
$GPGSV,6,6,23,539,35,307,27,541,12,162,21,544,14,199,25*73\r\n
$GAGSV,2,1,08,05,65,144,41,09,39,052,43,34,71,341,42,36,46,105,39*6A\r\n
$GAGSV,2,2,08,517,65,144,30,521,39,052,30,546,71,341,27,548,46,105,30*64\r\n
$GBGSV,3,1,10,11,09,141,34,14,52,047,44,27,32,313,43,28,80,263,44*64\r\n
$GBGSV,3,2,10,33,81,039,43,41,43,230,42,43,33,148,42,58,,,44*5B\r\n
$GBGSV,3,3,10,11,09,141,16,14,52,047,32*60\r\n
$GQGSV,1,1,01,02,45,101,30*49\r\n
$GLGSV,2,1,07,65,85,260,33,66,28,217,30,72,36,034,35,81,20,324,33*69\r\n
$GLGSV,2,2,07,87,47,127,35,88,73,350,34,87,47,127,20*53\r\n

Example NMEA version 4.11:

$GPGSV,4,1,14,02,40,310,43,08,07,324,31,10,48,267,45,15,37,053,45,1*67\r\n
$GPGSV,4,2,14,16,12,268,35,18,69,078,41,23,74,336,40,24,15,111,37,1*62\r\n
$GPGSV,4,3,14,26,02,239,31,27,35,307,38,29,12,162,37,32,14,199,39,1*60\r\n
$GPGSV,4,4,14,44,43,188,43,46,40,206,43,1*65\r\n
$GPGSV,3,1,09,10,48,267,45,15,37,053,26,18,69,078,34,23,74,336,34,6*68\r\n
$GPGSV,3,2,09,24,15,111,25,26,02,239,18,27,35,307,27,29,12,162,21,6*64\r\n
$GPGSV,3,3,09,32,14,199,25,6*58\r\n
$GAGSV,1,1,04,05,65,144,41,09,39,052,43,34,71,341,42,36,46,105,39,7*7E\r\n
$GAGSV,1,1,04,05,65,144,30,09,39,052,30,34,71,341,27,36,46,105,30,2*73\r\n
$GBGSV,2,1,08,11,09,141,34,14,52,047,44,27,32,313,43,28,80,263,44,1*71\r\n
$GBGSV,2,2,08,33,81,039,43,41,43,230,42,43,33,148,42,58,,,44,1*4E\r\n
$GBGSV,1,1,02,11,09,141,16,14,52,047,32,B*0D\r\n
$GQGSV,1,1,01,02,45,101,30,1*54\r\n
$GLGSV,2,1,06,65,85,260,33,66,28,217,30,72,36,034,35,81,20,324,33,1*75\r\n
$GLGSV,2,2,06,87,47,127,35,88,73,350,34,1*75\r\n
$GLGSV,1,1,01,87,47,127,20,3*41\r\n

Talker ID	Constellation
GP	GPS
GQ	QZSS
GA	Galileo
GL	Glonass
GB	BeiDou
GN	Combination of active constellations

Index	Field	Units	Description
1	numMsgs		Total number of messages for this constellation and epoch
2	msgNum		Message number
3	numSats		Total number of known satellites for the talker ID and signal ID
4+(n*5)	prn		Satellite PRN number
5+(n*5)	elev	deg	Elevation (0-90)
6+(n*5)	azim	deg	Azimuth (000 to 359)
7+(n*5)	snr	dB	SNR (00-99, empty when not tracking)
variable	system ID		GNSS system ID (distinguishes frequency band). This field is only output if the NMEA version is 4.11.

Where n is 0-3, for the four satellites supported by this message.

VTG

NMEA GPS track made good and speed over ground.

$GPVTG,140.88,T,,M,8.04,N,14.89,K,D*05\r\n
            1 2 3 4   5 6     7 8 9

| Index | Field | Units | Description | Example | |-------|--------|-------|----------------------------------------------------|---------| | 1 | track true | deg | Ground track heading (true north) | 140.88 | | 2 | T | | Ground track heading is relative to true north | T | | 3 | track mag | deg | Ground track heading (magnetic north) | | | 4 | M | | Ground track heading is relative to magnetic north (track mag = track true + magVarCorrection) | M | | 5 | speed Kn | knots | Speed | 8.04 | | 6 | N | | Speed is measured in knots | N | | 7 | speed Km | kph | Speed over ground in kilometers/hour | 14.89 | | 8 | K | | Speed over ground is measured in kph | K | | 9 | mode ind | | Mode indicator: | D | | | | | A: Autonomous mode | | | | | | D: Differential mode | | | | | | E: Estimated (dead reckoning) mode | | | | | | M: Manual Input mode | | | | | | S: Simulator mode | | | | | | N: Data not valid | |

PASHR

NMEA GPS DOP and active satellites.

$PASHR,001924.600,95.81,T,+0.60,+1.05,+0.00,0.038,0.035,0.526,0,0*08\r\n
          1         2   3   4      5    6    7      8     9  10 11  

Index	Field	Units	Description	Example
1	Time		UTC Time	001924.600
2	Heading		Heading value in decimal degrees	95.81
3	True Heading		T displayed if heading is relative to true north.	T
4	Roll	m	Roll in decimal degrees.	+0.60
5	Pitch	m	Pitch in decimal degrees.	+1.05
6	Heave	m	Instantaneous heave in meters.	+0.00
7	Roll Accuracy		Roll standard deviation in decimal degrees.	+0.038
8	Pitch Accuracy		Pitch standard deviation in decimal degrees.	0.035
9	Heading Accuracy		Heading standard deviation in decimal degrees.	0.526
10	GPS Status		GPS Status	0
11	INS Status		INS Status	0

PSTRB

Strobe input time. This message is sent when an assert event occurs on a strobe input pin.

$PSTRB,d,d,d,d*xx\r\n
       1 2 3 4

Index	Field	Units	Description
1	GPS week	weeks	Number of weeks since January 1st of 1980 in GMT
2	timeMsOfWeek	ms	Milliseconds since Sunday morning in GMT
3	pin		Strobe event input pin number
4	count		Strobe event serial index number

INFO

Device version information. Query this message by sending $INFO*0E\r\n.

$INFO,d,d.d.d.d,d.d.d.d,d,d.d.d.d,d,s,YYYY-MM-DD,hh:mm:ss.ms,s*xx\r\n
      1 2       3       4 5       6 7 8          9           10

Index	Field	Units	Description
1	Serial number		Manufacturer serial number
2	Hardware version		Hardware version
3	Firmware version		Firmware version
4	Build number		Firmware build number
5	Protocol version		Communications protocol version
6	Repo revision		Repository revision number
7	Manufacturer		Manufacturer name
8	Build date		Build date: [1] = year, [2] = month, [3] = day
9	Build time		Build date: [0] = hour, [1] = minute, [2] = second, [3] = millisecond
10	Add Info		Additional information
11	Hardware		Hardware: 1=uINS, 2=EVB, 3=IMX, 4=GPX
12	Reserved		Reserved for internal purpose.
13	Build type		Build type: 'a'=ALPHA, 'b'=BETA, 'c'=RELEASE CANDIDATE, 'r'=PRODUCTION RELEASE, 'd'=debug

NMEA Examples

Note

If the command strings below are altered, their checksum must be recalculated.

Note

All NMEA command strings must be followed with a carriage return and new line character (\r\n or 0x0D, 0x0A).

The NMEA string checksum is automatically computed and appended to string when using the InertialSense SDK serialPortWriteAscii function or can be generated using an online NMEA checksum calculator. For example: MTK NMEA checksum calculator

Stop streams on CURRENT port

$STPB*15                                     

Stop all streams on ALL ports

$ASCB,255,0,0,0,0,0,0,0,0,0,0,0,0*0D

Query device version information

$INFO*0E

Response:

$INFO,30612,3.1.2.0,1.7.0.0,3522,1.2.74.7,6275,Inertial Sense INC,0018-10-16,23:20:38.41,INL2*58

Stream INS1 @25Hz on port 0

$ASCB,1,,,40,,,,,,,,,*0A

Stream INS1 @10Hz on current port

$ASCB,0,,,100,,,,,,,,,*3E

Response:

$PINS1,244272.398,2021,427888998,805306448,0.0468,-0.3830,-0.0909,0.232,-0.083,-0.089,40.05574940,-111.65861580,1438.451,-1.678,-5.086,-9.697*11
$PINS1,244272.498,2021,427888998,805306448,0.0469,-0.3830,-0.0902,0.232,-0.081,-0.089,40.05575000,-111.65861550,1438.451,-1.611,-5.060,-9.697*18
$PINS1,244272.598,2021,427888998,805306448,0.0469,-0.3830,-0.0902,0.232,-0.081,-0.089,40.05575022,-111.65861562,1438.449,-1.587,-5.070,-9.695*1e

Stream INS1 @50Hz on serial port 1

$ASCB,2,,,20,,,,,,,,,*0F

Response:

$PINS1,256270.627,2021,427888998,1073741912,0.1153,-0.1473,-0.1628,0.001,0.001,0.003,40.05569486,-111.65864500,1416.218,-7.738,-7.570,12.536*3d
$PINS1,256270.647,2021,427888998,1073741912,0.1153,-0.1473,-0.1632,0.001,0.001,0.003,40.05569486,-111.65864500,1416.219,-7.738,-7.570,12.535*32
$PINS1,256270.667,2021,427888998,1073741912,0.1153,-0.1473,-0.1631,0.001,0.001,0.003,40.05569486,-111.65864500,1416.220,-7.738,-7.570,12.534*38

Stream PIMU @50Hz and GGA @5Hz on current port

$ASCB,0,20,0,0,0,0,0,200,0,0,0,0,0*3F

Response:

$PIMU,3218.543,0.0017,-0.0059,-0.0077,-1.417,-1.106,-9.524,0.0047,0.0031,-0.0069,-1.433,-1.072,-9.585*1f
$GPGGA,231841,4003.3425,N,11139.5188,W,1,29,0.89,1434.16,M,18.82,M,,*59
$PIMU,3218.563,0.0022,-0.0057,-0.0091,-1.416,-1.123,-9.512,0.0061,0.0035,-0.0068,-1.430,-1.091,-9.563*19
$PIMU,3218.583,0.0007,-0.0059,-0.0081,-1.420,-1.125,-9.508,0.0056,0.0047,-0.0086,-1.432,-1.078,-9.591*1e
$PIMU,3218.603,0.0015,-0.0062,-0.0077,-1.419,-1.130,-9.499,0.0069,0.0044,-0.0066,-1.434,-1.079,-9.579*10
$PIMU,3218.623,-0.0001,-0.0052,-0.0097,-1.413,-1.123,-9.529,0.0066,0.0047,-0.0072,-1.427,-1.085,-9.593*39
$PIMU,3218.643,0.0012,-0.0060,-0.0080,-1.423,-1.122,-9.508,0.0071,0.0047,-0.0070,-1.425,-1.083,-9.563*19
$PIMU,3218.663,-0.0004,-0.0065,-0.0088,-1.413,-1.118,-9.540,0.0057,0.0029,-0.0059,-1.430,-1.082,-9.604*3a
$PIMU,3218.683,-0.0001,-0.0064,-0.0096,-1.418,-1.121,-9.511,0.0059,0.0033,-0.0070,-1.431,-1.084,-9.585*39
$PIMU,3218.703,0.0007,-0.0055,-0.0079,-1.417,-1.128,-9.497,0.0046,0.0043,-0.0077,-1.428,-1.085,-9.565*18
$PIMU,3218.723,0.0024,-0.0054,-0.0085,-1.416,-1.106,-9.510,0.0051,0.0033,-0.0079,-1.429,-1.089,-9.588*1b
$PIMU,3218.743,0.0019,-0.0058,-0.0081,-1.430,-1.126,-9.533,0.0063,0.0032,-0.0073,-1.435,-1.093,-9.585*1d
$GPGGA,231841,4003.3425,N,11139.5188,W,1,29,0.89,1434.19,M,18.82,M,,*56
$PIMU,3218.763,0.0019,-0.0062,-0.0086,-1.426,-1.114,-9.509,0.0054,0.0029,-0.0070,-1.431,-1.085,-9.579*13

Using Tera Term App

The example NMEA command strings can be sent using standard serial port terminal that supports sending the line ending characters (carriage return and new line). The Windows desktop app Tera Term can be used for this.

Setup:

1. Start Tera Term > New connection. Select the correct serial port.

2. Setup > Terminal... - Receive: CR - Transmit: CR+LF (IMPORTANT - Ensures each NMEA string ends with \r\n or 0x0D, 0x0A) - Local echo: Yes This shows what was sent.

3. Setup > Serial port... - Speed: 921600 This is the default setting and must match the IMX serial port baudrate. - Data: 8 bit - Parity: none - Stop bits: 1 bit - Flow control: none

4. menu bar > setup > save setup - This saves time the next time Tera Term is used.

Saving a log:

1. File > log - Be sure to save as a .txt so it can be viewed in notepad. Controls for the log are in the Logger popup window after starting a log.

Sending an NMEA command:

1. Copy one of the command messages above to the clipboard.

2. Use the Tera Term > Edit > Paste<CR> option to send the copied command. This method in conjunction with the above "CR+LF" terminal transmit setting ensures that a carriage return and line feed character terminate the sent string. Only one NMEA string command can be sent at a time.