Communication & Messaging

1 Interfacing

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

  1. Serial (RS-422)

  2. UART (3.3V)

1.1 Serial Communication Parameters

Default Baud Rate:

  • 460800

Data Format:

  • Data Bits: 8

  • Stop Bits: 1

  • Parity: None

1.2 Time Synchronization

1.2.1 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.

2 ASCII Data Output Messages

ANELLO has two message formats, ASCII and Binary. 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

2.1 APIMU Message

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

3 Binary Data Output Messages

3.1 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=raw_int16*(accel_range*0.0000305)

Scaled sensor accel

3

AY1

int16

g=raw_int16*(accel_range*0.0000305)

Scaled sensor accel

4

AZ1

int16

g=raw_int16*(accel_range*0.0000305)

Scaled sensor accel

5

WX1

int16

dps=raw_int16*(mems_gyro_range*0.000035)

Scaled sensor rate

6

WY1

int16

dps=raw_int16*(mems_gyro_range*0.000035)

Scaled sensor rate

7

WZ1

int16

dps=raw_int16*(mems_gyro_range*0.000035)

Scaled sensor rate

8

OG_WX

int32

fog_dps = raw_int32 * (mems_gyro_range / 2^31)

Scaled sensor rate for FOG. MEMS gyro range is last 11 in MEMS Range field

9

OG_WY

int32

fog_dps = raw_int32 * (mems_gyro_range / 2^31)

Scaled sensor rate for FOG. MEMS gyro range is last 11 in MEMS Range field

10

OG_WZ

int32

fog_dps = raw_int32 * (mems_gyro_range / 2^31)

Scaled sensor rate for FOG. MEMS gyro range is last 11 in MEMS Range field

11

MAG_X

int16

mag_G = raw_int16 / 4096.0

Scaled magnetometer data

12

MAG_Y

int16

mag_G = raw_int16 / 4096.0

Scaled magnetometer data

13

MAG_Z

int16

mag_G = raw_int16 / 4096.0

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 degrees per second

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

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 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

4.3 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.

4.4 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

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
  }