Communication & Messaging

1 Interfacing

The communication interfaces currently supported for the ANELLO products are listed below:

1. ANELLO EVK: Serial (USB C), UDP (Ethernet)

2. ANELLO Ground INS: Serial (RS-232), UDP (Automotive Ethernet)

3. ANELLO Ground IMU: Serial (RS-232)

4. ANELLO X3: Serial (RS-422), UART (3.3V)

1.1 Serial Communication Parameters

Default Baud Rate:

• EVK: 921600

• Ground INS and Ground IMU: 230400

• X3: 460800

RS-232 Voltage Levels:

• +/- 7V

Data Format:

• Data Bits: 8

• Stop Bits: 1

• Parity: None

1.2 Port Definitions

For all interfaces, there are two main port types.

1. The data port is where the main ANELLO output messages are transmitted, and also serves as the input port for the RTCM correction stream.

2. The configuration port is used for inputting configuration messaging, inputting odometer messages, and outputting NMEA messages (firmware v1.2 and later).

For UDP interface, there is a third “odometer” port, which is strictly used to send odometer messages. This option can be used to feed in odometer data if using ANELLO Python Program to record data over serial, in order to keep the serial configuration port free.

Logical Port	Physical Port	Functions
Data Port	Lowest serial port #, e.g. COM7	Output: Data Messages Input: RTCM Data
	UDP: EVK port 1, computer port selectable
Configuration Port	Highest serial port #, e.g. COM10	Output: NMEA Messages (if configured) Input: Odometer Data, Configuration
	UDP: EVK port 2, computer port selectable
Odometer Port	UDP: EVK port 3, computer port selectable	Odometer Channel (UDP Only)

UDP communication uses fixed port numbers on the EVK but selectable ports on the external device. These ports, along with IP addresses and other UDP settings should be configured (see Unit Configurations).

Note

The “lowest” and “highest” serial ports mentioned above refer to the EVK, which uses an FTDI chip to create 4 virtual COM ports. The Ground INS and Ground IMU have two RS-232 connections, where RS232-1 is the configuration port and RS232-2 is the data port. The port numbers that appear once connected to the computer are determined by how the OS assigns the ports, and therefore the Data port is not necessarily the lowest port # like in the EVK.

1.3 Time Synchronization

1.3.1 External Sync Pulse

All ANELLO products include the option for time synchronization via an external sync pulse, e.g. from external PPS signal. To enable external synchronization, the “Sync Pulse Enable” Unit Configuration must be enabled. Enabling the sync configuration requires the unit to be reset or repowered as the interrupt is set up during MCU initialization. When “Sync Pulse Enable” is on, the rising edge of the sync pulse is detected by an interrupt and time-tagged in the IMU message “T_Sync” field.

The sync pulse input can be sent up to 100 Hz with a pulse width of at least 5 ms. A voltage level of 3.3 V is standard, but voltages from 1.5 to 5 V are also supported. See Mechanicals to find the sync input pin for each product.

1.3.2 PPS Synchronization

For the ANELLO Ground INS and EVK products which contain an internal GNSS receiver, a PPS output pulse is also supplied for time synchronization. PPS is output directly from the GNSS receiver, which will continue outputting a PPS pulse even if a GPS time fix is lost. Note that the PPS accuracy will degrade with time, with drifts around 1 us per second without GPS. See Mechanicals to find the PPS output pin for each product.

The PPS rising edge is also detected by an interrupt in the firmware. At the time of the interrupt, the MCU time is recorded by the firmware. The MCU time of the PPS interrupt is placed into the APINS message.

2 ASCII Data Output Messages

ANELLO has two message formats, ASCII and RTCM. The structures of all ASCII messages use the following conventions:

• The lead code identifier for each record is ‘#’

• All data fields are delimited by a comma

• Each log ends with a hexadecimal checksum preceded by an asterisk and followed by a line termination using the carriage return and line feed characters

• The checksum is an XOR of all the bytes between # and *, written in hexadecimal (letters must be uppercase)

• APIMU messages are transmitted at the output data rate (ODR) setting

• APINS messages are transmitted at 100 Hz

• APGPS messages are transmitted at 4 Hz

2.1.1 APIMU Message (EVK & Ground INS)

The APIMU message is the IMU output message for EVK and Ground INS units only.

	Field	Units	Description
0	APIMU		Sentence identifier
1	Time	ms	Time since power on
2	T_Sync	ms	Time at last sync rising edge (zero when sync config disabled)
3	AX	g	X-Axis Acceleration
4	AY	g	Y-Axis Acceleration
5	AZ	g	Z-Axis Acceleration
6	WX	deg/s	X-Axis Angular Rate (MEMS)
7	WY	deg/s	Y-Axis Angular Rate (MEMS)
8	WZ	deg/s	Z-Axis Angular Rate (MEMS)
9	OG_WZ	deg/s	High Precicision Z-Axis Angular Rate (ANELLO Optical Gyro)
10	ODO	m/s	Scaled Composite Odometer Value
11	ODO Time	ms	Timestamp of Odometer Reading
12	Temp	°C	Temperature

Note

Firmware before v1.0.39 does not have T_Sync field.

2.1.2 APIMU Message (X3)

This is the same as APIMU but with additional Optical Gyro Rates for 3 axes, magnetic field measurements, and without odometer values. This is the output message for X3 units only.

	Field	Units	Description
0	APIMU		Sentence identifier
1	Time	ms	Time since power on
2	T_Sync	ms	Time at last sync rising edge (zero when sync config disabled)
3	AX	g	X-Axis Acceleration
4	AY	g	Y-Axis Acceleration
5	AZ	g	Z-Axis Acceleration
6	WX	deg/s	X-Axis Angular Rate (MEMS)
7	WY	deg/s	Y-Axis Angular Rate (MEMS)
8	WZ	deg/s	Z-Axis Angular Rate (MEMS)
9	OG_WX	deg/s	High Precicision X-Axis Angular Rate (ANELLO Optical Gyro)
10	OG_WY	deg/s	High Precicision Y-Axis Angular Rate (ANELLO Optical Gyro)
11	OG_WZ	deg/s	High Precicision Z-Axis Angular Rate (ANELLO Optical Gyro)
12	MAG_X	g	X-Axis Magnetic Field Measurement
13	MAG_Y	g	X-Axis Magnetic Field Measurement
14	MAG_Z	g	X-Axis Magnetic Field Measurement
15	Temp C	°C	Temperature
16	Status_X	Bitfield	Status based on bits: - Bit 0: Gyro discrepency - Bit 1: Temperature uncontrolled - Bit 2: Over current error - Bit 3: SiPhOG supply voltage bad
17	Status_Y	Bitfield	Status based on bits: - Bit 0: Gyro discrepency - Bit 1: Temperature uncontrolled - Bit 2: Over current error - Bit 3: SiPhOG supply voltage bad
18	Status_Z	Bitfield	Status based on bits: - Bit 0: Gyro discrepency - Bit 1: Temperature uncontrolled - Bit 2: Over current error - Bit 3: SiPhOG supply voltage bad

2.1.3 APIM1 Message (Ground IMU)

The APIM1 message is the same as APIMU but without odometer values. This is the output message for Ground IMU units only.

	Field	Units	Description
0	APIMU		Sentence identifier
1	Time	ms	Time since power on
2	T_Sync	ms	Time at last sync rising edge (zero when sync config disabled)
3	AX	g	X-Axis Acceleration
4	AY	g	Y-Axis Acceleration
5	AZ	g	Z-Axis Acceleration
6	WX	deg/s	X-Axis Angular Rate (MEMS)
7	WY	deg/s	Y-Axis Angular Rate (MEMS)
8	WZ	deg/s	Z-Axis Angular Rate (MEMS)
9	OG_WZ	deg/s	High Precicision Z-Axis Angular Rate (ANELLO Optical Gyro)
12	Temp C	°C	Temperature

Note

Firmware before v1.0.39 does not have T_Sync field.

2.2 APGPS Message

The APGPS message is the PVT output from the EVK and Ground INS units only.

	Field	Units	Description
0	APGPS		Sentence identifier
1	Time	ms	Time since power on
2	GPS Time	ns	GPS Time in integer ns
3	Lat	deg	Latitude, ‘+’: north, ‘-’: south
4	Long	deg	Longitude, ‘+’: east, ‘-’: west
5	Alt ellipsoid	m	Height above ellipsoid
6	Alt msl	m	Height above mean sea level
7	Speed	m/s	GNSS Speed
8	Heading	deg	GNSS Heading (ground track)
9	Hacc	m	Horizontal Accuracy
10	Vacc	m	Vertical Accuracy
11	PDOP		Position dilution of precision
12	FixType		0: No Fix, 2: 2D Fix, 3: 3D Fix, 5: Time Only
13	SatNum		Number of satellites used in solution
14	Speed Acc		Accuracy of GNSS Speed measurement
15	Hdg Acc		Accuracy of GNSS Heading measurement
16	RTK Status		0: Single Point Positioning, 1: RTK Float, 2: RTK Fixed

Note

This packet should be used to correlate GPS time and system time. The packet is time stamped at the time the PPS signal is generated by the GNSS receiver.

2.3 APHDG Message

The APHDG message contains dual heading information from the dual GNSS receivers if both ANT1 and ANT2 are connected. This message is output from the EVK and Ground INS units only.

	Field	Units	Description
0	APHDG		Sentence identifier
1	Time	ms	Time since power on
2	GPS Time	ns	GPS Time in integer ns (not UTC time)
3	relPosN	m	North component of relative position vector
4	relPosE	m	East component of relative position vector
5	relPosD	m	Down component of relative position vector
6	relPosLength	m	Length of relative position vector between antennae
7	relPosHeading	deg	Heading from primary antenna to secondary antenna
8	RelPosLength Accuracy	m	Accuracy of dual antennae baseline length
9	relPosHeading Accuracy	deg	Accuracy of dual antennae heading
10	flags		Status based on bits: - Bit 0: gnssFixOK - Bit 1: diffSoln - Bit 2: relPosValid - Bits 4..3: carrSoln - Bit 5: isMoving - Bit 6: refPosMiss - Bit 7: refObsMiss - Bit 8: relPosHeading Valid - Bit 9: relPos Normalized

2.4 APINS Message

The APINS message is the Kalman filter position, velocity, and attitude solution output from the EVK and Ground INS units.

	Field	Units	Description
0	APINS		Sentence identifier
1	Time	ms	Time since power on
2	PPS Time	ns	Time of last PPS pulse converted to GPS time (time since midnight on Jan 6, 1980)
3	Status		0: Attitude Only 1: Position and Attitude 2: Position, Attitude, and Heading 3: RTK Float 4: RTK Fix If GPS button is turned OFF in Python tool: 8: Attitude Only 9: Position and Attitude 10: Position, Attitude, and Heading
4	Lat	deg	Latitude, ‘+’: North, ‘-’: South
5	Long	deg	Longitude, ‘+’: East, ‘-’: West
6	Height	m	Height above ellipsoid
7	VN	m/s	North Velocity in NED Frame
8	VE	m/s	East Velocity in NED Frame
9	VD	m/s	Down Velocity in NED Frame
10	Roll	deg	Roll Angle, rotation about body frame X
11	Pitch	deg	Pitch Angle, rotation about body frame Y
12	Heading	deg	Heading Angle, rotation about body frame Z
13	ZUPT		0: Moving, 1: Stationary

Note

Roll, pitch and heading angles are calculated as standard aerospace Euler angles in a 3-2-1 (yaw, pitch, roll) body frame rotation.

2.5 APAHRS Message

The APAHRS message is only available with the ANELLO AHRS upgrade on the Ground IMU. It provides the roll, pitch and yaw angles calculated as standard aerospace Euler angles in a 3-2-1 (yaw, pitch, roll) body frame rotation.

	Field	Units	Description
0	APINS		Sentence identifier
1	Time	ms	Time since power on
2	Sync Time	ns	Time of the last sync pulse.
3	Roll	deg	Roll in degrees
4	Pitch	deg	Pitch in degrees
5	Yaw	deg	Yaw in degrees
6	ZUPT Status		1 if ZUPT is enabled, 0 if ZUPT is disabled

Note

The yaw is not an absolute heading but an integrated relative heading - unless an absolute heading is provided by the user, after which the optical gyro integrates relative to that absolute heading.

3 RTCM Binary Data Output Messages

The binary packets use an RTCM standard 10403 envelope for each message.

	Field	Value/Description
0	Preamble	0xD3
1	Reserved	000000 (6 bit)
2	Length	10 bit, # bytes in data message
3	Data	Data message as defined below
4	CRC	3 byte

The ANELLO Python Tool handles logging and decoding of the RTCM binary format. However, an RTCM decoder is provided if needed, with the checksum definition found here.

3.1.1 IMU Message (EVK & Ground INS)

The IMU output message for EVK and Ground INS units has a subtype ID of 1.

	Field	Type	Units	Description
0	Message #	uint12	4058	ANELLO Photonics custom message number
1	Sub Type ID	uint4	1
2	MCU Time	uint64	ns	Time since power on
3	Sync Time	uint64	ns	Timestamp of input sync pulse (if enabled and provided)
4	ODO Time	uint64	ns	Timestamp of odometer reading
5	AX	int32	1/143165577 g	X-Axis Acceleration (intended 15g/2^31)
6	AY	int32	1/143165577 g	Y-Axis Acceleration
7	AZ	int32	1/143165577 g	Z-Axis Acceleration
8	WX	int32	1/4772186 deg/s	X-Axis Angular Rate (MEMS) (intended 450/2^31)
9	WY	int32	1/4772186 deg/s	Y-Axis Angular Rate (MEMS)
10	WZ	int32	1/4772186 deg/s	Z-Axis Angular Rate (MEMS)
11	OG_WZ	int32	1/4772186 deg/s	High precision optical gyro z-axis angular rate
12	ODO	int16	0.01 m/s	Scaled composite odometer value
13	Temp C	int16	0.01 °C	Temperature

3.1.2 IMU Message (X3)

The ANELLO binary packets use a 2-byte preamble followed by a 1-byte message type and a 1-byte length. There is also a 2-byte checksum after the payload.

Preamble	Message Type	Length information	Payload	Checksum
0xC5 0x50	IMU = 253	1-byte	Message structure defined below	2-byte

The payload for the binary output message is described below

	Field	Type	Units	Description
0	MCU Time	uint64	ns	Time since power on
1	Sync Time	uint64	ns	Timestamp of input sync pulse (if enabled and provided)
2	AX1	int16	g=value*(range*0.0000305)	Scaled sensor accel
3	AY1	int16	g=value*(range*0.0000305)	Scaled sensor accel
4	AZ1	int16	g=value*(range*0.0000305)	Scaled sensor accel
5	WX1	int16	dps=value*(range*0.000035)	Scaled sensor rate
6	WY1	int16	dps=value*(range*0.000035)	Scaled sensor rate
7	WZ1	int16	dps=value*(range*0.000035)	Scaled sensor rate
8	OG_WX	int32	dps * 2147483648 / MEMS Gyro Range	Scaled sensor rate for FOG. MEMS gyro range is last 11 in MEMS Range field
9	OG_WY	int32	dps * 2147483648 / MEMS Gyro Range	Scaled sensor rate for FOG. MEMS gyro range is last 11 in MEMS Range field
10	OG_WZ	int32	dps * 2147483648 / MEMS Gyro Range	Scaled sensor rate for FOG. MEMS gyro range is last 11 in MEMS Range field
11	MAG_X	int16	g * 4096	Scaled magnetometer data
12	MAG_Y	int16	g * 4096	Scaled magnetometer data
13	MAG_Z	int16	g * 4096	Scaled magnetometer data
14	Temperature	int16	°C * 100	Scaled temperature data
15	MEMS Range	uint16	g and dps	First 5 bits accel range, next 11 bits rate range
16	FOG Range	uint16	dps	FOG range in DPS
17	Status_X	Bitfield		Status based on bits: - Bit 0: Gyro discrepency - Bit 1: Temperature uncontrolled - Bit 2: Over current error - Bit 3: SiPhOG supply voltage bad - Bits 4-7: Reserved.
18	Status_Y	Bitfield		Status based on bits: - Bit 0: Gyro discrepency - Bit 1: Temperature uncontrolled - Bit 2: Over current error - Bit 3: SiPhOG supply voltage bad - Bits 4-7: Reserved.
19	Status_Z	Bitfield		Status based on bits: - Bit 0: Gyro discrepency - Bit 1: Temperature uncontrolled - Bit 2: Over current error - Bit 3: SiPhOG supply voltage bad - Bits 4-7: Reserved.

3.1.3 IM1 Message (Ground IMU)

The IMU output message for Ground IMU units has a subtype ID of 6. It is the same as IMU message for the EVK and Ground INS but without odometer values.

	Field	Type	Units	Description
0	Message #	uint12	4058	ANELLO Photonics custom message number
1	Sub Type ID	uint4	6
2	MCU Time	uint64	ns	Time since power on
3	Sync Time	uint64	ns	Timestamp of input sync pulse (if enabled and provided)
4	AX	int32	1/143165577 g	X-Axis Acceleration (intended 15g/2^31)
5	AY	int32	1/143165577 g	Y-Axis Acceleration
6	AZ	int32	1/143165577 g	Z-Axis Acceleration
7	WX	int32	1/4772186 deg/s	X-Axis Angular Rate (MEMS) (intended 450/2^31)
8	WY	int32	1/4772186 deg/s	Y-Axis Angular Rate (MEMS)
9	WZ	int32	1/4772186 deg/s	Z-Axis Angular Rate (MEMS)
10	OG_WZ	int32	1/4772186 deg/s	High precision optical gyro z-axis angular rate
11	Temp C	int16	0.01 °C	Temperature

3.3 GPS PVT Message (EVK/Ground INS)

The GPS message is the PVT output from the EVK and Ground INS units only. The Antenna ID field indicates which receiver (that connected to ANT1 or ANT2) produced the position information.

	Field	Type	Units	Description
0	Message #	uint12	4058
1	Sub Type ID	uint4	2
2	Time	uint64	ns	Time since power on
3	GPS Time	uint64	ns	GPS time (GTOW) – Time since Jan 6, 1980
4	Latitude	int32	1e-7 deg	Latitude, ‘+’: north, ‘-’: south
5	Longitude	int32	1e-7 deg	Longitude, ‘+’: east, ‘-’: west
6	Alt ellipsoid	int32	0.001 m	Height above ellipsoid
7	Alt msl	int32	0.001 m	Height above mean sea level
8	Speed	int32	0.001 m/s	Speed
9	Heading	int32	0.001 deg	GNSS Heading (ground track)
10	Hacc	uint32	0.001 m	Horizontal accuracy
11	Vacc	uint32	0.001 m	Vertical accuracy
12	Hdg acc	uint32	1e-5 deg	Heading accuracy
13	Speed acc	uint32	0.001 m/s	Speed accuracy
14	PDOP	uint16	0.01	Position dilution of precision
15	FixType	uint8		0: No Fix, 2: 2D Fix, 3: 3D Fix, 5: Time Only
16	SatNum	uint8		Number of Satellites used in solution
17	RTK Status	uint8		0: Single Point Positioning, 1: RTK Float, 2: RTK Fixed
18	Antenna ID	uint8		Primary or secondary antenna

3.4 HDG Message (EVK/Ground INS)

The HDG message contains dual heading information from the dual GNSS receivers if both ANT1 and ANT2 are connected. This message is output from the EVK and Ground INS units only.

	Field	Type	Units	Description
0	Message #	uint12	4058	ANELLO Photonics custom message number
1	Sub Type ID	uint4	3
2	MCU Time	uint64	ns	Time since power on
3	GPS Time	uint64	ns	GPS time (GTOW) – Time since Jan 6, 1980
4	relPosN	int32	0.01 m	North component of relative position vector
5	relPosE	int32	0.01 m	East component of relative position vector
6	relPosD	int32	0.01 m	Down component of relative position vector
7	relPosLength	int32	0.01 m	Length of relative position vector between antennae
8	relPosHeading	int32	1e-5 deg	Heading from primary antenna to secondary antenna
9	relPosLength Accuracy	uint32	0.1 mm	Accuracy of dual antennae baseline length
10	relPosHeading Accuracy	uint32	1e-5 deg	Accuracy of dual antennae heading
11	flags	uint16_t		Status based on bits: - Bit 0: gnssFixOK - Bit 1: diffSoln - Bit 2: relPosValid - Bits 4..3: carrSoln - Bit 5: isMoving - Bit 6: refPosMiss - Bit 7: refObsMiss - Bit 8: relPosHeading Valid - Bit 9: relPos Normalized

3.5 INS Message (EVK/Ground INS)

The INS message is the Kalman filter position, velocity, and attitude solution output from the EVK and Ground INS units.

	Field	Type	Units	Description
0	Message #	uint12	4058
1	Sub Type ID	uint4	4
2	Time	uint64	ns	Time since power on
3	PPS Time	uint64	ns	Time of last PPS pulse converted to GPS time (time since midnight on Jan 6, 1980)
4	Latitude	int32	1e-7 deg	Latitude, ‘+’: north, ‘-’: south
5	Longitude	int32	1e-7 deg	Longitude, ‘+’: east, ‘-’: west
6	Alt ellipsoid	int32	0.001 m	Height above ellipsoid
7	VN	int32	0.001 m/s	North Velocity in NED Frame
8	VE	int32	0.001 m/s	East Velocity in NED Frame
9	VD	int32	0.001 m/s	Down Velocity in NED Frame
10	Roll	int32	1e-5 deg	Roll Angle, rotation about body frame X
11	Pitch	int32	1e-5 deg	Pitch Angle, rotation about body frame Y
12	Heading	int32	1e-5 deg	Heading Angle, rotation about body frame Z
13	ZUPT	uint8		0: Moving, 1: Stationary
14	Status	uint8		0: Attitude Only; 1: Position and Attitude; 2: Position, Attitude, and Heading; 3: RTK Float; 4: RTK Fix If GPS button is turned OFF in Python tool, 8: Attitude Only; 9: Position and Attitude; 10: Position, Attitude, and Heading

3.6 AHRS Message (Ground IMU)

The APAHRS message is only available with the ANELLO AHRS upgrade on the Ground IMU. It provides the roll, pitch and yaw angles calculated as standard aerospace Euler angles in a 3-2-1 (yaw, pitch, roll) body frame rotation.

	Field	Type	Units	Description
0	Message #	uint12	4058
1	Sub Type ID	uint4	8
2	Time	uint64	ns	Time since power on
3	Sync Time	uint64	ns	Time of last sync pulse.
4	Roll	int32	1e-5 deg	Roll in degrees
5	Pitch	int32	1e-5 deg	Pitch in degrees
6	Yaw	int32	1e-5 deg	Yaw in degrees
7	ZUPT Status	uint8	1 or 0	1 if ZUPT is enabled, 0 if ZUPT is disabled

Note

The yaw is not an absolute heading but an integrated relative heading - unless an absolute heading is provided by the user, after which the optical gyro integrates relative to that absolute heading.

4 Input Messages

4.1 APCFG Messages

The easiest way to configure an ANELLO unit is using the ANELLO Python Program, which saves all changes to non-volatile flash memory.

Alternatively, the unit can be configured using the APCFG message, which allows for both temporary (RAM) and permanent setting (FLASH) of configuration parameters.

#APCFG,<r/w/R/W>,<param1>,<value1>,…,<paramN>,<valueN>*checksum

	Field	Description
0	APCFG	Sentence identifier
1	<read/write>	‘r’: read RAM, ‘w’: write RAM, ‘R’: read FLASH, ‘W’: write FLASH
2	<param>	Configuration parameter (APCFG code)
3	<value>	Configuration value, expressed in ASCII
4	checksum	XOR of bytes between # and * written in hexadecimal (letters must be uppercase)

For more details on configuration parameters and values, see Unit Configurations.

4.2 APVEH Messages

The easiest way to set ANELLO vehicle configurations is using the ANELLO Python Program, which saves all changes to non-volatile flash memory.

Alternatively, the unit can be configured using the APVEH message, which allows for both temporary (RAM) and permanent setting (FLASH) of configuration parameters.

#APVEH,<r/w/R/W>,<param1>,<value1>,…,<paramN>,<valueN>*checksum

	Field	Description
0	APVEH	Sentence identifier
1	<read/write>	‘r’: read RAM, ‘w’: write RAM, ‘R’: read FLASH, ‘W’: write FLASH
2	<param>	Configuration parameter (APVEH code)
3	<value>	Configuration value, expressed in ASCII
4	checksum	XOR of bytes between # and * written in hexadecimal (letters must be uppercase)

4.3 APODO Message

The ANELLO EVK and Ground INS accepts odometer input over the configuration port. The APODO message is in ASCII format and used to convey the vehicle direction and a speed. A negative value indicates reverse, and a positive value indicates forward. If no direction is indicated, the direction is assumed to be forward.

Direction can also be input without a speed. This can be useful when there is no odometer input available, but transmission position is available. This is useful to enable INS initialization in both forward and reverse.

When an APODO message is received with a reverse direction indication, the unit will assume the vehicle is in reverse until a packet is received with a forward direction. The units of the speed in the APODO message is user configurable to m/s (default), mile/hr, km/hr, ft/s (see ‘odo’ code in Unit Configurations).

#APODO,<dir>,<speed>*checksum

	Field	Description
0	APODO	Sentence identifier
1	<dir>	‘-’: reverse, ‘+’: forward (optional)
2	<speed>	Speed is a floating point value, units are set in unit configurations
3	checksum	XOR of bytes between # and * written in hexadecimal (letters must be uppercase)

For example, the following would all be interpreted as moving in reverse with a speed of 24: #APODO,-,24*7E #APODO,-24*52 #APODO,-,-24*53

Note

If sending odometer speeds by UDP from another program, send to UDP port 3 on the EVK, from the computer’s UDP port matching “odometer port” configuration.

4.4 RTCM Data Input

Standard RTCM messages can be forwarded to the data port of the ANELLO EVK and Ground INS to enable the GNSS receivers to reach RTK precision. Standard RTCM3.3 in MSM format, including MSM4, MSM5, and MSM7 messages, are supported. The ANELLO Python Program provides an NTRIP client which can connect to a standard NTRIP network and forward the RTCM messages to the ANELLO unit.

4.5 Ping Command

The Ping command can be used to test if the serial port is properly configured.

#APPNG*48

A correctly received ping command generates a response from the unit of:

#APPNG,0*54

4.6 Echo Command

The Echo command serves as an additional communication test for the serial port configuration as well as the checksum generator. For example:

#APECH,Echo! echo… ech… e…*77

A correctly received Echo command generates an identical response from the unit:

#APECH,Echo! echo… ech… e…*77.

4.7 Reset Command

The reset command allows the user to reset the system, e.g. after changing a configuration setting that requires a power cycle. No response message is generated; however, the system will reset causing the system output to be suspended briefly.

#APRST,0*58

5 Error Messages

If an incorrect command is sent to the unit, it responds with one of ten error responses. The error message format is:

#APERR,<error code>*CS

The following table lists the error code along with the corresponding description.

Error Code	Description
1	No start character (#)
2	Read/Write indicator missing (from #APCFG or #APVEH)
3	Incomplete message (checksum missing)
4	Incorrect checksum
5	Invalid preamble (AP)
6	Invalid message type
7	Invalid field
8	Invalid value
9	Flash locked
10	Unexpected character (applies to APPID, APSTA, APVER, APSER, APFSN, and APFHW)
11	Disabled command (applies to APODO)

6 Checksum

6.1 Ascii Checksum

The ASCII checksum is an XOR of all characters between the start character ‘#’ and the checksum indicator ‘*’. The following python code snippet can be used to generate the correct checksum.

• Specify the input message (generates the string: #APCFG,W,odr,2,msg,IMU*4B)

• Generate the checksum for the inertial product input message

• Print the complete message (starting field and checksum) to the screen

msg = bytearray(APCFG,W,odr,2,msg,IMU)
checksum = 0
for c in msg:
  checksum = checksum ^ int(c)
print(#%s*%02X % (msg.decode(), checksum))

6.2 Binary Checksum

Ground INS, EVK, Ground IMU:

The checksum definition can be found here.

X3:

The 2 preamble bytes and the checksum itself are not included in the checksum calculation. Checksum is calculated as follows, where N is the number of bytes included in the checksum calculation:

CK_A = 0
CK_B = 0
for (I = 0; I < N; I++)
{
CK_A = CK_A + Buffer[I]
CK_B = CK_B + CK_A
}

return CK_A, CK_B

Note

The checksum is a two-byte value (CK_A, CK_B). In the reference implementation, these bytes are appended to the end of the message buffer (the last two bytes).