Codec

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Introduction

A codec is a device or computer program for encoding or decoding a digital data stream or signal. Codec is a portmanteau of coder – decoder. A codec encodes a data stream or a signal for transmission and storage, possibly in encrypted form, and the decoder function reverses the encoding for playback or editing.

Below you will see a table of all Codec types with ID’s:

Codec 8 Codec 8 Extended Codec 16 Codec 12 Codec 13 Codec 14
0x08 0x8E 0x10 0x0C 0x0D 0x0E

Also, there are using two data transport protocols: TCP and UDP. But it is not important which one will be use in Codec.

Codec for device data sending

In this chapter you will find information about every Codec protocol which are using for device data sending and differences between them.

Codec 8

  • Protocol Overview

Codec8 – a main FM device protocol that is used for sending data to server.

  • Codec8 protocol sending over TCP

TCP is a connection-oriented protocol that is using for communication between devices. How this type protocol works you will read later.

  • AVL Data Packet

Below table represents AVL Data Packet structure:

0x00000000 (Preamble) Data Field Length Codec ID Number of Data 1 AVL Data Number of Data 2 CRC-16
4 bytes 4 bytes 1 byte 1 byte X bytes 1 byte 4 bytes

Preamble – the packet starts with four zero bytes.
Data Field Length – size is calculated starting from Codec ID to Number of Data 2.
Codec ID – in Codec8 it is always 0x08.
Number of Data 1 – a number which defines how many records is in the packet.
AVL Data – actual data in the packet (more information below).
Number of Data 2 – a number which defines how many records is in the packet. This number must be the same as “Number of Data 1”.
CRC-16 – calculated from Codec ID to the Second Number of Data. CRC (Cyclic Redundancy Check) is an error-detecting code using for detect accidental changes to RAW data. For calculation we are using CRC-16/IBM. More information about it you can found here.

Note: for FMB6XY and FM63XY, minimum AVL packet size is 45 bytes (all IO elements disabled). Maximum AVL packet size is 255 bytes. For other devices, minimum AVL packet size is 45 bytes (all IO elements disabled). Maximum AVL packet size is 1280 bytes.

  • AVL Data

Below table represents AVL Data structure.

Timestamp Priority GPS Element IO Element
8 bytes 1 byte 15 bytes X bytes

Timestamp – a difference, in milliseconds, between the current time and midnight, January, 1970 UTC (UNIX time).
Priority – field which define AVL data priority (more information below).
GPS Element – locational information of the AVL data (more information below).
IO Element – additional configurable information from device (more information below).

  • Priority

Below table represents Priority values. Packet priority depends on device configuration and records sent.

Priority
0 Low
1 High
2 Panic


  • GPS element

Below table represents GPS Element structure:

Longitude Latitude Altitude Angle Satellites Speed
4 bytes 4 bytes 2 bytes 2 bytes 1 byte 2 bytes

Longitude – east – west position.
Latitude – north – south position.
Altitude – meters above sea level.
Angle – degrees from north pole.
Satellites – number of visible satellites.
Speed – speed calculated from satellites.

Note: Speed will be 0x0000 if GPS data is invalid.

Longitude and latitude are integer values built from degrees, minutes, seconds and milliseconds by formula:
GPS.png
Where:
d – Degrees; m – Minutes; s – Seconds; ms – Milliseconds; p – Precision (10000000)
If longitude is in west or latitude in south, multiply result by –1.

Note:
To determine if the coordinate is negative, convert it to binary format and check the very first bit. If it is 0, coordinate is positive, if it is 1, coordinate is negative.

Example:
Received value: 20 9C CA 80 converted to BIN: 00100000 10011100 11001010 10000000 first bit is 0, which means coordinate is positive converted to DEC: 547146368. For more information see two‘s complement arithmetic.

  • IO Element
Event IO ID 1 byte Event IO ID – if data is acquired on event – this field defines which IO property has changed and generated an event. For example, when if Ignition state changed and it generate event, Event IO ID will be 0xEF (AVL ID: 239). If it’s not eventual record – the value is 0.

N – a total number of properties coming with record (N = N1 + N2 + N4 + N8).
N1 – number of properties, which length is 1 byte.
N2 – number of properties, which length is 2 bytes.
N4 – number of properties, which length is 4 bytes.
N8 – number of properties, which length is 8 bytes.
N’th IO ID - AVL ID.
N’th IO Value - AVL ID value.

N of Total IO 1 byte
N1 of One Byte IO 1 byte
1’st IO ID 1 byte
1’st IO Value 1 byte
...
N1’th IO ID 1 byte
N1’th IO Value 1 byte
N2 of Two Bytes 1 byte
1’st IO ID 1 byte
1’st IO Value 2 bytes
...
N2’th IO ID 1 byte
N2’th IO Value 2 bytes
N4 of Four Bytes 1 byte
1’st IO ID 1 byte
1’st IO Value 4 bytes
...
N4’th IO ID 1 byte
N4’th IO Value 4 byte
N8 of Eight Bytes 1 byte
1’st IO ID 1 byte
1’st IO Value 8 byte
...
N8’IO ID 1 byte
N8’IO Value 8 bytes



  • Communication with server

First, when module connects to server, module sends its IMEI. First comes short identifying number of bytes written and then goes IMEI as text (bytes).
For example, IMEI 356307042441013 would be sent as 000F333536333037303432343431303133.
First two bytes denote IMEI length. In this case 0x000F means, that IMEI is 15 bytes long.
After receiving IMEI, server should determine if it would accept data from this module. If yes, server will reply to module 01, if not - 00. Note that confirmation should be sent as binary packet. I.e. 1 byte 0x01 or 0x00.
Then module starts to send first AVL data packet. After server receives packet and parses it, server must report to module number of data received as integer (four bytes).
If sent data number and reported by server doesn’t match module resends sent data.

  • Example:

Module connects to server and sends IMEI:
000F333536333037303432343431303133
Server accepts the module:
01
Module sends data packet:

AVL Data Packet Header AVL Data Array CRC-16
Four Zero Bytes – 0x00000000,

“AVL Data Array” length – 0x000000FE

Codec ID – 0x08,

Number of Data – 0x02
(Encoded using continuous bit stream. Last byte padded to align to byte boundary)

CRC of “AVL Data Array”
00000000000000FE 0802...(data elements)...02 00008612


Server acknowledges data reception (2 data elements): 00000002

  • Examples

Hexadecimal stream of AVL Data Packet receiving and response in these examples are given in hexadecimal form. The different fields of packets are seperate into different table columns for better readability and some of them are coverted to ASCII values for better understanding.

1'st example
Receiving one data record with each element property (1 byte, 2 bytes, 4 byte and 8 byte).

Received data in hexadecimal stream:
000000000000003608010000016B40D8EA30010000000000000000000000000000000105021503010101425E0F01F10000601A014E0000000000000000010000C7CF

Parsed:

AVL Data Packet
AVL Data Packet Part HEX Code Part
Zero Bytes 00 00 00 00
Data Field Length 00 00 00 36
Codec ID 08
Number of Data 1 (Records) 01
AVL Data Timestamp 00 00 00 01 6B 40 D8 EA 30 (GMT: Monday, June 10, 2019 10:04:46 AM)
Priority 01
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 01
N of Total ID 05
N1 of One Byte IO 02
1’st IO ID 15 (AVL ID: 21, Name: GSM Signal)
1’st IO Value 03
2’nd IO ID 01 (AVL ID: 1, Name: DIN1)
2’nd IO Value 01
N2 of Two Bytes IO 01
1’st IO ID 42 (AVL ID: 66, Name: External Voltage)
1’st IO Value 5E 0F
N4 of Four Bytes IO 01
1’st IO ID F1 (AVL ID: 241, Name: Active GSM Operator)
1’st IO Value 00 00 60 1A
N8 of Eight Bytes IO 01
1’st IO ID 4E (AVL ID: 78, Name: iButton)
1’st IO Value 00 00 00 00 00 00 00 00
Number of Data 2 (Number of Total Records) 01
CRC-16 00 00 C7 CF


Server response: 00000001

2'nd example
Receiving one data record with one or two different element properties (1 byte, 2 byte).

Received data in hexadecimal stream:
000000000000002808010000016B40D9AD80010000000000000000000000000000000103021503010101425E100000010000F22A

Parsed:

AVL Data Packet
AVL Data Packet Part HEX Code Part
Zero Bytes 00 00 00 00
Data Field Length 00 00 00 28
Codec ID 08
Number of Data 1 (Records) 01
AVL Data Timestamp 00 00 01 6B 40 D9 AD 80 (GMT: Monday, June 10, 2019 10:05:36 AM)
Priority 01
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 01
N of Total ID 03
N1 of One Byte IO 02
1’st IO ID 15 (AVL ID: 21, Name: GSM Signal)
1’st IO Value 03
2’nd IO ID 01 (AVL ID: 1, Name: DIN1)
2’nd IO Value 01
N2 of Two Bytes IO 01
1’st IO ID 42 (AVL ID: 66, Name: External Voltage)
1’st IO Value 5E 0F
N4 of Two Bytes IO 00
N8 of Two Bytes IO 00
Number of Data 2 (Number of Total Records) 01
CRC-16 00 00 F2 2A


Server response: 00000001

3'rd example
Receiving two or more data records with one or more different element properties.

Received data in hexadecimal stream:
000000000000004308020000016B40D57B480100000000000000000000000000000001010101000000000000016B40D5C198010000000000000000000000000000000 101010101000000020000252C

Parsed:

AVL Data Packet
AVL Data Packet Part HEX Code Part
Zero Bytes 00 00 00 00
Data Field Length 00 00 00 43
Codec ID 08
Number of Data 1 (Records) 02
AVL Data

(1'st record)

Timestamp 00 00 01 6B 40 D5 7B 48 (GMT: Monday, June 10, 2019 10:01:01 AM)
Priority 01
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 01
N of Total ID 01
N1 of One Byte IO 01
1’st IO ID 01 (AVL ID: 1, Name: DIN1)
1’st IO Value 00
N2 of Two Bytes IO 00
N4 of Two Bytes IO 00
N8 of Two Bytes IO 00
AVL Data

(2'nd record)

Timestamp 00 00 01 6B 40 D5 C1 98 (GMT: Monday, June 10, 2019 10:01:19 AM)
Priority 01
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 01
N of Total ID 01
N1 of One Byte IO 01
1’st IO ID 01 (AVL ID: 1, Name: DIN1)
1’st IO Value 01
N2 of Two Bytes IO 00
N4 of Two Bytes IO 00
N8 of Two Bytes IO 00
Number of Data 2 (Number of Total Records) 01
CRC-16 00 00 25 2C


Server response: 00000002

  • Codec8 protocol sending over UDP

UDP is a transport layer protocol above UDP/IP to add reliability to plain UDP/IP using acknowledgment packets.

  • AVL Data Packet

The packet structure is as follows:

UDP Datagram
Example 2 bytes
Packet ID 2 bytes
Not Usable Byte 1 byte
Packet Payload Variable

Example – packet length (excluding this field) in big ending byte order.
Packet ID – packet ID unique for this channel.
Not Usable Byte – not usable byte.
Packet payload – data payload.

  • Acknowledgment packet

Acknowledgment packet should have the same Packet ID as acknowledged data packet and empty Data Payload. Acknowledgement should be sent in binary format.

Acknowledgment Packet
Packet Length Packet ID Not Usable Byte
2 bytes 2 bytes 1 byte

Packet Length – packet length by sending/response data.
Packet ID – same as in acknowledgment packet.
Not Usable Byte – always will be 0x01.

  • Sending AVL Packet Payload using UDP channel

Below table represents Sending Packet Payload structure.

AVL data encapsulated in UDP channel packet
AVL Packet ID IMEI Length Module IMEI AVL Data Array
1 byte 2 bytes 15 bytes X bytes

AVL Packet ID – ID identifying this AVL packet.
IMEI Length – always will be 0x000F.
Module IMEI – IMEI of a sending module encoded the same as with TCP.
AVL Data Array – array of encoded AVL data (same as TCP AVL Data Array).

  • Server response Packet Payload using UDP channel

Below table represents Server Response Packet Payload structure.

Server Response to AVL Data Packet
AVL Packet ID Number of Accepted AVL Elements
1 byte 1 byte


  • Communication with server

Module sends UDP channel packet with encapsulated AVL data packet. Server sends UDP channel packet with encapsulated response module validates AVL Packet ID and Number of accepted AVL elements. If server response with valid AVL Packet ID is not received within configured timeout, module can retry sending.

  • Example:

Module sends the data:

UDP Channel Header AVL Packet Header AVL Data Array
Length – 0x00FE,

Packet ID – 0xCAFE
Not Usable Byte – 0x01

AVL Packet ID – 0xDD,

IMEI Length – 0x000F
IMEI – 0x313233343536373839303132333435 (Encoded using continuous bit stream. Last byte padded to align to byte boundary)

Codec ID – 0x08,

Number of Data – 0x02
(Encoded using continuous bit stream)

00FECAFE01 DD000F3133343536373839303132333435 0802…(data elements)…02



Server must respond with acknowledgment:

UDP Channel Header AVL Packet Acknowledgment
Length – 0x0005,

Packet ID – 0xCAFE, Not Usable Byte – 0x01

AVL Packet ID – 0xDD,

Number of Accepted Data – 0x02

0005CAFE01 DD02



  • Example

Hexadecimal stream of AVL Data Packet receiving and response in this example are given in hexadecimal form. The different fields of packet are seperate into different table columns for better readability and some of them are coverted to ASCII values for better understanding.

Received data in hexadecimal stream:
003DCAFE0105000F33353230393330383634303336353508010000016B4F815B30010000000000000000000000000000000103021503010101425DBC000001

Parsed:

AVL Data Packet
AVL Data Packet Part HEX Code Part
UDP Channel Header Length 00 3D
Packet ID CA FE
Not usable byte 01
AVL Packet Header AVL packet ID 05
IMEI Length 00 0F
IMEI 33 35 32 30 39 33 30 38 36 34 30 33 36 35 35
AVL Data Array Codec ID 08
Number of Data 1 (Records) 01
Timestamp 00 00 01 6B 4F 81 5B 30 (GMT: Thursday, June 13, 2019 6:23:26 AM)
Priority 01
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 01
N of Total ID 03
N1 of One Byte IO 02
1’st IO ID 15 (AVL ID: 21, Name: GSM Signal)
1’st IO Value 03
2’nd IO ID 01 (AVL ID: 1, Name: DIN1)
2’nd IO Value 01
N2 of Two Bytes IO 01
1’st IO ID 42 (AVL ID: 66, Name: External Voltage)
1’st IO Value 5D BC
N4 of Two Bytes IO 00
N8 of Two Bytes IO 00
Number of Data 2 (Number of Total Records) 01



Server response in hexademical stream: 0005CAFE010501

Parsed:

Server Response to AVL Data Packet
Server Response Part HEX Code Part
UDP Channel Header Length 00 05
Packet ID CA FE
Not usable byte 01
AVL Packet Acknowledgment AVL packet ID 05
Number of Accepted Data 01



Codec 8 Extended

  • Protocols overview

Codec8 Extended is using for FMBXXX family devices. This protocol looks familiar like Codec8 but they have some differences. Main differences between are shown in below table:

Codec8 Codec8 Extended
Codec ID 0x08 0x8E
AVL Data IO element length 1 byte 2 bytes
AVL Data IO element total IO count length 1 byte 2 bytes
AVL Data IO element IO count length 1 byte 2 bytes
AVL Data IO element AVL ID length 1 byte 2 bytes
Variable size IO elements Does not include Includes variable size elements



  • Codec 8 Extended protocol sending over TCP
  • AVL data packet

Below table represents AVL data packet structure:

0x00000000 (Preamble) Data Field Length Codec ID Number of Data 1 AVL Data Number of Data 2 CRC-16
4 bytes 4 bytes 1 byte 1 byte X bytes 1 byte 4 bytes

Preamble – the packet starts with four zero bytes.
Data Field Length – size is calculated starting from Codec ID to Number of Data 2.
Codec ID – in Codec8 it is always 0x08.
Number of Data 1 – a number which defines how many records is in the packet.
AVL Data – actual data in the packet (more information below).
Number of Data 2 – a number which defines how many records is in the packet. This number must be the same as “Number of Data 1”.
CRC-16 – calculated from Codec ID to the Second Number of Data. CRC (Cyclic Redundancy Check) is an error-detecting code using for detect accidental changes to RAW data. For calculation we are using CRC-16/IBM. More information about it you can found here.

Note: for FMB6XY and FM63XY, minimum AVL packet size is 45 bytes (all IO elements disabled). Maximum AVL packet size is 255 bytes. For other devices, minimum AVL packet size is 45 bytes (all IO elements disabled). Maximum AVL packet size is 1280 bytes.

  • AVL Data

Below table represents AVL Data structure:

Timestamp Priority GPS Element IO Element
8 bytes 1 byte 15 bytes X bytes

Timestamp – a difference, in milliseconds, between the current time and midnight, January, 1970 UTC (UNIX time).
Priority – field which define AVL data priority (more information below).
GPS Element – locational information of the AVL data (more information below).
IO Element – additional configurable information from device (more information below).

  • Priority

Below table represents Priority values. Packet priority depends on device configuration and records sent.

Priority
0 Low
1 High
2 Panic



  • GPS element

Below table represents GPS Element structure:

Longitude Latitude Altitude Angle Satellites Speed
4 bytes 4 bytes 2 bytes 2 bytes 1 byte 2 bytes

Longitude – east – west position.
Latitude – north – south position.
Altitude – meters above sea level.
Angle – degrees from north pole.
Satellites – number of visible satellites.
Speed – speed calculated from satellites.

Note: Speed will be 0x0000 if GPS data is invalid.

Longitude and latitude are integer values built from degrees, minutes, seconds and milliseconds by formula:
GPS.png
Where:
d – Degrees; m – Minutes; s – Seconds; ms – Milliseconds; p – Precision (10000000)
If longitude is in west or latitude in south, multiply result by –1.

Note:
To determine if the coordinate is negative, convert it to binary format and check the very first bit. If it is 0, coordinate is positive, if it is 1, coordinate is negative.

Example:
Received value: 20 9C CA 80 converted to BIN: 00100000 10011100 11001010 10000000 first bit is 0, which means coordinate is positive converted to DEC: 547146368. For more information see two‘s complement arithmetic.

  • IO Element
Event IO ID 2 bytes Event IO ID – if data is acquired on event – this field defines which IO property has changed and generated an event. For example, when if Ignition state changed and it generate event, Event IO ID will be 0xEF (AVL ID: 239). If it’s not eventual record – the value is 0.

N – a total number of properties coming with record (N = N1 + N2 + N4 + N8).
N1 – number of properties, which length is 1 byte.
N2 – number of properties, which length is 2 bytes.
N4 – number of properties, which length is 4 bytes.
N8 – number of properties, which length is 8 bytes.
NX – a number of properties, which length is defined by length element. N’th IO ID - AVL ID.
N'th Lenght - AVL ID value lenght.
N’th IO Value - AVL ID value.

N of Total IO 2 bytes
N1 of One Byte IO 2 bytes
1’st IO ID 2 bytes
1’st IO Value 1 byte
...
N1’th IO ID 2 bytes
N1’th IO Value 1 byte
N2 of Two Bytes 2 bytes
1’st IO ID 2 bytes
1’st IO Value 2 bytes
...
N2’th IO ID 2 bytes
N2’th IO Value 2 bytes
N4 of Four Bytes 2 bytes
1’st IO ID 2 bytes
1’st IO Value 4 bytes
...
N4’th IO ID 2 bytes
N4’th IO Value 4 byte
N8 of Eight Bytes 2 bytes
1’st IO ID 2 bytes
1’st IO Value 8 byte
...
N8’IO ID 2 bytes
N8’IO Value 8 bytes
NX of X Byte IO 2 bytes
1’st IO ID 2 bytes
1’st IO Length 2 bytes
1’st IO Value Defined by lenght
...
NX’th IO ID 2 bytes
NX’th Length 2 bytes
NX’th Value Defined by lenght



  • Communication with server

Communication with server is the same as with Codec8 protocol, except in Codec8 Extended protocol Codec ID is 0x8E.

  • Example:

Module connects to server and sends IMEI:
000F333536333037303432343431303133
Server accepts the module:
01
Module sends data packet:

AVL Data Packet Header AVL Data Array CRC-16
Four Zero Bytes – 0x00000000,

“AVL Data Array” length – 0x000000FE

Codec ID – 0x8E,

Number of Data – 0x02
(Encoded using continuous bit stream. Last byte padded to align to byte boundary)

CRC of “AVL Data Array”
00000000000000FE 8E02...(data elements)...02 00008612


Server acknowledges data reception (2 data elements): 00000002

  • Example

Hexadecimal stream of AVL Data Packet receiving and response in this example are given in hexadecimal form. The different fields of packet are seperate into different table columns for better readability and some of them are coverted to ASCII values for better understanding.

Received data in hexadecimal stream:
000000000000004A8E010000016B412CEE000100000000000000000000000000000000010005000100010100010011001D00010010015E2C880002000B000000003544C87 A000E000000001DD7E06A00000100002994

Parsed data:

AVL Data Packet
AVL Data Packet Part HEX Code Part
Zero Bytes 00 00 00 00
Data Field Length 00 00 00 4A
Codec ID 8E
Number of Data 1 (Records) 01
AVL Data Timestamp 00 00 01 6B 41 2C EE 00 (GMT: Monday, June 10, 2019 11:36:32 AM)
Priority 01
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 00 01
N of Total ID 00 05
N1 of One Byte IO 00 01
1’st IO ID 00 01 (AVL ID: 1, Name: DIN1)
1’st IO Value 01
N2 of Two Bytes IO 00 01
1’st IO ID 00 11 (AVL ID: 17, Name: Axis X)
1’st IO Value 00 1D
N4 of Two Bytes IO 00 01
1’st IO ID 00 10 (AVL ID: 16, Name: Total Odometer)
1’st IO Value 01 5E 2C 88
N8 of Two Bytes IO 00 02
1’st IO ID 00 0B (AVL ID: 11, Name: ICCID1)
1’st IO Value 00 00 00 00 35 44 C8 7A
2’nd IO ID 00 0E (AVL ID: 14, Name: ICCID2)
2’nd IO Value 00 00 00 00 1D D7 E0 6A
NX of X Byte IO 00 00
Number of Data 2 (Number of Total Records) 01
CRC-16 00 00 29 94


Server response: 00000001

  • Codec8 Extended protocol sending over UDP
  • UDP channel protocol

AVL data packet is the same as with Codec8, except Codec ID is changed to 0x8E.

  • Communication with server

Module sends UDP channel packet with encapsulated AVL data packet. Server sends UDP channel packet with encapsulated response module validates AVL Packet ID and Number of accepted AVL elements. If server response with valid AVL Packet ID is not received within configured timeout, module can retry sending.

  • Example:

Module sends the data:

UDP Channel Header AVL Packet Header AVL Data Array
Length – 0x00FE,

Packet ID – 0xCAFE
Not Usable Byte – 0x01

AVL Packet ID – 0xDD,

IMEI Length – 0x000F
IMEI – 0x313233343536373839303132333435 (Encoded using continuous bit stream. Last byte padded to align to byte boundary)

Codec ID – 0x8E,

Number of Data – 0x02
(Encoded using continuous bit stream)

00FECAFE01 DD000F3133343536373839303132333435 8E02…(data elements)…02


Server must respond with acknowledgment:

UDP Channel Header AVL Packet Acknowledgment
Length – 0x0005,

Packet ID – 0xCAFE, Not Usable Byte – 0x01

AVL Packet ID – 0xDD,

Number of Accepted Data – 0x02

0005CAFE01 DD02



  • Example

Hexadecimal stream of AVL Data Packet receiving and response in this example are given in hexadecimal form. The different fields of packet are seperate into different table columns for better readability and some of them are coverted to ASCII values for better understanding.

Received data in hexadecimal stream:
005FCAFE0107000F3335323039333038363430333635358E010000016B4F831C680100000000000000000000000000000000010005000100010100010011009D000100 10015E2C880002000B000000003544C87A000E000000001DD7E06A000001

Parsed:

AVL Data Packet
AVL Data Packet Part HEX Code Part
UDP Channel Header Length 00 5F
Packet ID CA FE
Not usable byte 01
AVL Packet Header AVL packet ID 05
IMEI Length 00 0F
IMEI 33 35 32 30 39 33 30 38 36 34 30 33 36 35 35
AVL Data Array Codec ID 8E
Number of Data 1 (Records) 01
Timestamp 00 00 01 6B 4F 83 1C 68 (GMT: Thursday, June 13, 2019 6:25:21 AM)
Priority 01
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 00 01
N of Total ID 00 05
N1 of One Byte IO 00 01
1’st IO ID 00 01 (AVL ID: 1, Name: DIN1)
1’st IO Value 00 01
N2 of Two Bytes IO 00 01
1’st IO ID 00 11 (AVL ID: 17, Name: Axis X)
1’st IO Value 00 1D
N4 of Two Bytes IO 00 01
1’st IO ID 00 10 (AVL ID: 16, Name: Total Odometer)
1’st IO Value 01 5E 2C 88
N8 of Two Bytes IO 00 02
1’st IO ID 00 0B (AVL ID: 11, Name: ICCID1)
1’st IO Value 00 00 00 00 35 44 C8 7A
2’nd IO ID 00 0E (AVL ID: 14, Name: ICCID2)
2’nd IO Value 00 00 00 00 1D D7 E0 6A
NX of X Byte IO 00 00



Server response in hexademical stream: 0005CAFE010700

Parsed:

Server Response to AVL Data Packet
Server Response Part HEX Code Part
UDP Channel Header Length 00 05
Packet ID CA FE
Not usable byte 01
AVL Packet Acknowledgment AVL packet ID 07
Number of Accepted Data 00



Codec 16

  • Protocol overview

Codec16 is using for FMB630/FM63XY devices. This protocol looks familiar like Codec8 but they have some differences. Main differences between are shown in table below:

Codec8 Codec16
Codec ID 0x08 0x10
AVL Data IO element ID event length 1 byte 2 bytes
AVL Data IO element AVL ID length 1 byte 2 bytes
Generation Type Not Using Is Using



Note: Codec16 is supported from firmware – 00.03.xx and newer. (FMB630/FM63XY) || AVL ID‘s which are higher than 255 will can be used only in Codec 16 protocol.

  • Codec 16 protocol sending over TCP
  • AVL data packet

Below table represents AVL data packet structure:

0x00000000 (Preamble) Data Field Length Codec ID Number of Data 1 AVL Data Number of Data 2 CRC-16
4 bytes 4 bytes 1 byte 1 byte X bytes 1 byte 4 bytes

Preamble – the packet starts with four zero bytes.
Data Field Length – size is calculated starting from Codec ID to Number of Data 2.
Codec ID – in Codec16 it is always 0x10.
Number of Data 1 – a number which defines how many records is in the packet.
AVL Data – actual data in the packet (more information below).
Number of Data 2 – a number which defines how many records is in the packet. This number must be the same as “Number of Data 1”.
CRC-16 – calculated from Codec ID to the Second Number of Data. CRC (Cyclic Redundancy Check) is an error-detecting code using for detect accidental changes to RAW data. For calculation we are using CRC-16/IBM. More information about it you can found here.

Note: for FMB6XY and FM63XY, minimum AVL packet size is 45 bytes (all IO elements disabled). Maximum AVL packet size is 255 bytes.

  • AVL Data

Below table represents AVL Data structure:

Timestamp Priority GPS Element IO Element
8 bytes 1 byte 15 bytes X bytes

Timestamp – a difference, in milliseconds, between the current time and midnight, January, 1970 UTC (UNIX time).
Priority – field which define AVL data priority (more information below).
GPS Element – locational information of the AVL data (more information below).
IO Element – additional configurable information from device (more information below).

  • Priority

Below table represents Priority values. Packet priority depends on device configuration and records sent.

Priority
0 Low
1 High
2 Panic



  • GPS element

Below table represents GPS Element structure:

Longitude Latitude Altitude Angle Satellites Speed
4 bytes 4 bytes 2 bytes 2 bytes 1 byte 2 bytes

Longitude – east – west position.
Latitude – north – south position.
Altitude – meters above sea level.
Angle – degrees from north pole.
Satellites – number of visible satellites.
Speed – speed calculated from satellites.

Note: Speed will be 0x0000 if GPS data is invalid.

Longitude and latitude are integer values built from degrees, minutes, seconds and milliseconds by formula:
GPS.png
Where:
d – Degrees; m – Minutes; s – Seconds; ms – Milliseconds; p – Precision (10000000)
If longitude is in west or latitude in south, multiply result by –1.

Note:
To determine if the coordinate is negative, convert it to binary format and check the very first bit. If it is 0, coordinate is positive, if it is 1, coordinate is negative.

Example:
Received value: 20 9C CA 80 converted to BIN: 00100000 10011100 11001010 10000000 first bit is 0, which means coordinate is positive converted to DEC: 547146368. For more information see two‘s complement arithmetic.

  • IO Element
Event IO ID 2 bytes Event IO ID – if data is acquired on event – this field defines which IO property has changed and generated an event. For example, when if Ignition state changed and it generate event, Event IO ID will be 0xEF (AVL ID: 239). If it’s not eventual record – the value is 0.

Generation type - data event generation type. More information about it you can find here.
N – a total number of properties coming with record (N = N1 + N2 + N4 + N8).
N1 – number of properties, which length is 1 byte.
N2 – number of properties, which length is 2 bytes.
N4 – number of properties, which length is 4 bytes.
N8 – number of properties, which length is 8 bytes.
N’th IO ID - AVL ID.
N’th IO Value - AVL ID value.

Generation Type 1 byte
N of Total IO 1 byte
N1 of One Byte IO 1 byte
1’st IO ID 2 bytes
1’st IO Value 1 byte
...
N1’th IO ID 2 bytes
N1’th IO Value 1 byte
N2 of Two Bytes 1 byte
1’st IO ID 2 bytes
1’st IO Value 2 bytes
...
N2’th IO ID 2 bytes
N2’th IO Value 2 bytes
N4 of Four Bytes 1 byte
1’st IO ID 2 bytes
1’st IO Value 4 bytes
...
N4’th IO ID 2 bytes
N4’th IO Value 4 byte
N8 of Eight Bytes 1 byte
1’st IO ID 2 bytes
1’st IO Value 8 byte
...
N8’IO ID 2 bytes
N8’IO Value 8 bytes



  • Generation type
Value Record Created
0 On Exit
1 On Entrance
2 On Both
3 Reserved
4 Hysteresis
5 On Change
6 Eventual
7 Periodical



  • Communication with server

Communication with server is the same as with Codec8 protocol, except in Codec16 protocol Codec ID is 0x10 and has generation type.

  • Example:

Module connects to server and sends IMEI:
000F333536333037303432343431303133
Server accepts the module:
01
Module sends data packet:

AVL Data Packet Header AVL Data Array CRC-16
Four Zero Bytes – 0x00000000,

“AVL Data Array” length – 0x000000FE

Codec ID – 0x10,

Number of Data – 0x02
(Encoded using continuous bit stream. Last byte padded to align to byte boundary)

CRC of “AVL Data Array”
00000000000000FE 1002...(data elements)...02 00008612


Server acknowledges data reception (2 data elements): 00000002

  • Example

Hexadecimal stream of AVL Data Packet receiving and response in this example are given in hexadecimal form. The different fields of packet are seperate into different table columns for better readability and some of them are coverted to ASCII values for better understanding.

Received data in hexadecimal stream:
000000000000005F10020000016BDBC7833000000000000000000000000000000000000B05040200010000030002000B00270042563A00000000016BDBC78718 00000000000000000000000000000000000B05040200010000030002000B00260042563A00000200005FB3

Parsed data:

AVL Data Packet
AVL Data Packet Part HEX Code Part
Zero Bytes 00 00 00 00
Data Field Length 00 00 00 5F
Codec ID 10
Number of Data 1 (Records) 02
AVL Data

(1'st record)

Timestamp 00 00 01 6B DB C7 83 30 (GMT: Wednesday, July 10, 2019 12:06:54 PM)
Priority 01
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 00 0B
Generation Type 05
N of Total ID 04
N1 of One Byte IO 02
1’st IO ID 00 01 (AVL ID: 1, Name: DIN1)
1’st IO Value 00
2’nd IO ID 00 03 (AVL ID: 3, Name: DIN3)
2’nd IO Value 00
N2 of Two Bytes IO 02
1’st IO ID 00 0B (AVL ID: 11, Name: ICCID1)
1’st IO Value 00 27
2’nd IO ID 00 42 (AVL ID: 66, Name: External Voltage)
2’nd IO Value 56 3A
N4 of Two Bytes IO 00
N8 of Two Bytes IO 00
AVL Data

(2'nd record)

Timestamp 00 00 01 6B DB C7 87 18 (GMT: Wednesday, July 10, 2019 12:06:55 PM)
Priority 01
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 00 0B
Generation Type 05
N of Total ID 04
N1 of One Byte IO 02
1’st IO ID 00 01 (AVL ID: 1, Name: DIN1)
1’st IO Value 00
2’nd IO ID 00 03 (AVL ID: 3, Name: DIN3)
2’nd IO Value 00
N2 of Two Bytes IO 02
1’st IO ID 00 0B (AVL ID: 11, Name: ICCID1)
1’st IO Value 00 26
2’nd IO ID 00 42 (AVL ID: 66, Name: External Voltage)
2’nd IO Value 56 3A
N4 of Two Bytes IO 00
N8 of Two Bytes IO 00
Number of Data 2 (Number of Total Records) 02
CRC-16 00 00 5F B3


Server response: 00000002

  • Codec16 Extended protocol sending over UDP
  • UDP channel protocol

AVL data packet is the same as with Codec8, except Codec ID is changed to 0x10.

  • Communication with server

Module sends UDP channel packet with encapsulated AVL data packet. Server sends UDP channel packet with encapsulated response module validates AVL Packet ID and Number of accepted AVL elements. If server response with valid AVL Packet ID is not received within configured timeout, module can retry sending.

  • Example:

Module sends the data:

UDP Channel Header AVL Packet Header AVL Data Array
Length – 0x00FE,

Packet ID – 0xCAFE
Not Usable Byte – 0x01

AVL Packet ID – 0xDD,

IMEI Length – 0x000F
IMEI – 0x313233343536373839303132333435 (Encoded using continuous bit stream. Last byte padded to align to byte boundary)

Codec ID – 0x10,

Number of Data – 0x02
(Encoded using continuous bit stream)

00FECAFE01 DD000F3133343536373839303132333435 1002…(data elements)…02



Server must respond with acknowledgment:

UDP Channel Header AVL Packet Acknowledgment
Length – 0x0005,

Packet ID – 0xCAFE, Not Usable Byte – 0x01

AVL Packet ID – 0xDD,

Number of Accepted Data – 0x02

0005CAFE01 DD02



  • Example

Hexadecimal stream of AVL Data Packet receiving and response in this example are given in hexadecimal form. The different fields of packet are seperate into different table columns for better readability and some of them are coverted to ASCII values for better understanding.

Received data in hexadecimal stream:
015BCAFE0101000F33353230393430383532333135393210070000015117E40FE80000000000000000000000000000000000EF05050400010000030000B4000 0EF01010042111A000001

Parsed:

AVL Data Packet
AVL Data Packet Part HEX Code Part
UDP Channel Header Length 01 5B
Packet ID CA FE
Not usable byte 01
AVL Packet Header AVL packet ID 07
IMEI Length 00 0F
IMEI 33 35 32 30 39 34 30 38 35 32 33 31 35 39 32
AVL Data Array Codec ID 10
Number of Data 1 (Records) 01
Timestamp 00 00 01 51 17 E4 0F E8 (GMT: Wednesday, November 18, 2015 12:00:01 AM)
Priority 00
Longitude 00 00 00 00
Latitude 00 00 00 00
Altitude 00 00
Angle 00 00
Satellites 00
Speed 00 00
Event IO ID 00 EF
Generation type 05
N of Total ID 05
N1 of One Byte IO 04
1’st IO ID 00 01 (AVL ID: 1, Name: DIN1)
1’st IO Value 00
2’nd IO ID 00 03 (AVL ID: 3, Name: DIN3)
2’nd IO Value 00
3’rd IO ID 00 B4 (AVL ID: 180, Name: DOUT2)
3’rd IO Value 00
4’th IO ID 00 EF (AVL ID: 239, Name: Ignition)
4’th IO Value 00
N2 of Two Bytes IO 01
1’st IO ID 42 (AVL ID: 66, Name: External Voltage)
1’st IO Value 11 1A
N4 of Two Bytes IO 00
N8 of Two Bytes IO 00
Number of Data 2 (Number of Total Records) 01



Server response in hexademical stream: 0005CAFE010700

Parsed:

Server Response to AVL Data Packet
Server Response Part HEX Code Part
UDP Channel Header Length 00 05
Packet ID CA FE
Not usable byte 01
AVL Packet Acknowledgment AVL packet ID 07
Number of Accepted Data 00



Differences between Codec 8, Codec 8 Extended and Codec 16

In the table below you will see differences between Codec8, Codec8 Extended and Codec16.

Codec8 Codec8 Extended Codec16
Codec ID 0x08 0x8E 0x10
AVL Data IO element length 1 byte 2 bytes 2 bytes
AVL Data IO element total IO count length 1 byte 2 bytes 2 bytes
Generation Type Is Using Not Using Is Using
AVL Data IO element IO count length 1 byte 2 bytes 1 byte
AVL Data IO element AVL ID length 1 byte 2 bytes 2 bytes
Variable size IO elements Does not include Includes variable size elements Does not include



Codec for communication over GPRS messages

In this chapter you will find information about every Codec protocol which are using for communication over GPRS messages and differences between them.

Codec 12

  • About Codec12

Codec12 is original and main Teltonika protocol for device-server communication over GPRS messages. Codec12 GPRS commands can be used for sending configuration, debug, digital outputs control commands or other (special purpose command on special firmware versions). This protocol is also necessary for using FMB630/FM6300/FM5300/FM5500/FM4200 features like: Garmin, LCD communication, COM TCP Link Mode.

  • GPRS command session

Following figure shows how GRPS command session is started over TCP.
Codec12.png First, Teltonika device opens GPRS session and sends AVL data to server (refer device protocols). Once all records are sent and correct sent data array acknowledgment is received by device then GPRS commands in Hex can be sent to device.
The ACK (acknowledge of IMEI from server) is a one byte constant 0x01. The acknowledgement of each data array send from device is four bytes integer – number of records received.
Note, that GPRS session should remain active between device and server, while GPRS commands are sent. For this reason, active datalink timeout (global parameters in device configuration) is recommended to be set to 259200 (maximum value).

  • General Codec12 message structure

The following diagram shows basic structure of Codec 12 messages.

Command message structure:

0x00000000 (Preamble) Data Size Codec ID Command Quantity 1 Type (0x05) Command Size Command Command Quantity 2 CRC-16
4 bytes 4 bytes 1 byte 1 byte 1 byte 4 bytes X bytes 1 byte 4 bytes



Response message structure:

0x00000000 (Preamble) Data Size Codec ID Response Quantity 1 Type (0x06) Response Size Response Response Quantity 2 CRC-16
4 bytes 4 bytes 1 byte 1 byte 1 byte 4 bytes X bytes 1 byte 4 bytes

Preamble - the packet starts with four zero bytes.
Data Size - size is calculated from Codec ID field to the second command or response quantity field.
Codec ID - in Codec12 it is always 0x0C.
Command/Response Quantity 1 - it is ignored when parsing the message.
Type - it can be 0x05 to denote command or 0x06 to denote response.
Command/Response Size – command or response length.
Command/Response – command or response in HEX.
Command/Response Quantity 2 - a byte which defines how many records (commands or responses) is in the packet. This byte will not be parsed but it’s recommended that it should contain same value as Command/Response Quantity 1.
CRC-16 - calculated from Codec ID to the Command/Response Quantity 2. CRC (Cyclic Redundancy Check) is an error-detecting code using for detect accidental changes to RAW data. For calculation we are using CRC-16/IBM. More information about it you can found here.

Note that difference between commands and responses is message type field: 0x05 means command and 0x06 means response.

  • Command coding table

Command has to be converted from ASCII characters (char) to hexadecimal (HEX):
ASCII.png

  • Command parsing example

Hexadecimal stream of command and answer in this example are given in hexadecimal form. The different fields of message are seperate into different table columns for better readability and understanding.

  • GPRS commands examples

Hexadecimal stream of GPRS command and answer in these examples are given in hexadecimal form. The different fields of messages are seperate into different table columns for better readability and some of them are coverted to ASCII values for better understanding.

1'st example: Sending getinfo SMS command via GPRS Codec12

Server request in hexadecimal stream:
000000000000000F0C010500000007676574696E666F0100004312

Parsed:

Server Command
Server Command Part HEX Code Part
Zero Bytes 00 00 00 00
Data Size 00 00 00 0F
Codec ID 0C
Command Quantity 1 01
Command Type 05
Command Size 00 00 00 07
Command 67 65 74 69 6E 66 6F
Command Quantity 2 01
CRC-16 00 00 43 12


Note that Server Command converted from HEX to ASCII means getinfo

Device response in hexadecimal stream:
00000000000000900C010600000088494E493A323031392F372F323220373A3232205254433A323031392F372F323220373A3533205253543A32204552523A 312053523A302042523A302043463A302046473A3020464C3A302054553A302F302055543A3020534D533A30204E4F4750533A303A3330204750533A312053 41543A302052533A332052463A36352053463A31204D443A30010000C78F

Parsed:

Device Answer
Device Answer Part HEX Code Part
Zero Bytes 00 00 00 00
Data Size 00 00 00 90
Codec ID 0C
Response Quantity 1 01
Response Type 06
Response Size 00 00 00 88
Response 49 4E 49 3A 32 30 31 39 2F 37 2F 32 32 20 37 3A 32 32 20 52 54 43 3A 32 30 31 39 2F 37 2F 32 32 20 37 3A 35 33 20 52 53 54 3A 32 20 45 52 52 3A 31 20 53 52 3A 30 20 42 52 3A 30 20 43 46 3A 30 20 46 47 3A 30 20 46 4C 3A 30 20 54 55 3A 30 2F 30 20 55 54 3A 30 20 53 4D 53 3A 30 20 4E 4F 47 50 53 3A 30 3A 33 30 20 47 50 53 3A 31 20 53 41 54 3A 30 20 52 53 3A 33 20 52 46 3A 36 35 20 53 46 3A 31 20 4D 44 3A 30
Response Quantity 2 01
CRC-16 00 00 C7 8F


Note that Device Response converted from HEX to ASCII means:
INI:2019/7/22 7:22 RTC:2019/7/22 7:53 RST:2 ERR:1 SR:0 BR:0 CF:0 FG:0 FL:0 TU:0/0 UT:0 SMS:0 NOGPS:0:30 GPS:1 SAT:0 RS:3 RF:65 SF:1 MD:0

2'nd xample: Sending getio SMS command via GPRS Codec12

Server request in hexadecimal stream:
000000000000000D0C010500000005676574696F01000000CB

Parsed:

Server Command
Server Command Part HEX Code Part
Zero Bytes 00 00 00 00
Data Size 00 00 00 0D
Codec ID 0C
Command Quantity 1 01
Command Type 05
Command Size 00 00 00 05
Command 67 65 74 69 6F
Command Quantity 2 01
CRC-16 00 00 00 CB


Note that Server Command converted from HEX to ASCII means getio

Device response in hexadecimal stream:
00000000000000370C01060000002F4449313A31204449323A30204449333A302041494E313A302041494E323A313639323420444F313A3020444F323A3101000066E3

Parsed:

Device Answer
Device Answer Part HEX Code Part
Zero Bytes 00 00 00 00
Data Size 00 00 00 37
Codec ID 0C
Response Quantity 1 01
Response Type 06
Response Size 00 00 00 2F
Response 44 49 31 3A 31 20 44 49 32 3A 30 20 44 49 33 3A 30 20 41 49 4E 31 3A 30 20 41 49 4E 32 3A 31 36 39 32 34 20 44 4F 31 3A 30 20 44 4F 32 3A 31
Response Quantity 2 01
CRC-16 00 00 66 E3


Note that Device Response converted from HEX to ASCII means:
DI1:1 DI2:0 DI3:0 AIN1:0 AIN2:16924 DO1:0 DO2:1

  • Communication with server

The GSM/GPRS commands can be sent from a terminal program. We recommend to use Hercules (in TCP server mode). Simply write command as explained below into Hercules Send field, check HEX box and click Send button. Note that the TCP server must be listening on specified port (see Port field and Listen button below).

Hercules.jpeg

  • FMXX and Codec12 functionality
  • Garmin

All information is provided in “FMXX and Garmin development.pdf” document.

  • COM TCP Link Mode

All information is provided in “FMxx TCP Link mode test instructions.pdf” document.

Codec 13

  • About Codec13

Codec13 is original Teltonika protocol for device-server communication over GPRS messages and it is based on Codec12 protocol. Main differences of Codec13 are that timestamp is using in messages and communication is one way only (Codec13 is used for Device -> Server sending).

  • General Codec13 message structure

The following diagram shows basic structure of Codec 13 messages:

0x00000000 (Preamble) Data Size Codec ID Command Quantity 1 Type Command Size Timestamp Command Command Quantity 2 CRC-16
4 bytes 4 bytes 1 byte 1 byte 1 byte 4 bytes 8 bytes X bytes 1 byte 4 bytes

4 Zeros – the packet starts with preamble field (four zero bytes).
Data Size – size is calculated from Codec ID field to the second Command Quantity field.
Codec ID – in Codec13 it is always 0x0D.
Command Quantity 1 – 0x01, it is ignored when parsing the message.
Command Type – it is always 0x05 since the packet is direction is FM->Server.
Command Size – command size field includes size of timestamp too, so it is equal to size of payload + size of timestamp.
Timestamp – a difference, in milliseconds, between the current time and midnight, January, 1970 UTC (UNIX time).
Command – actual received data.
Command Quantity 2 – a byte which defines how many records (commands) is in the packet. This byte will not be parsed but it’s recommended that it should contain same value as Command/Response Quantity 1.
CRC-16 - calculated from Codec ID to Command Quantity 2. CRC (Cyclic Redundancy Check) is an error-detecting code using for detect accidental changes to RAW data. For calculation we are using CRC-16/IBM. More information about it you can found here.

Note: Codec13 packets are used only when “Message Timestamp” parameter in RS232 settings is enabled.

  • Command parsing example

Hexadecimal stream of GPRS command in this example is given in hexadecimal form. The different fields of message are seperate into different table columns for better readability and some of them are coverted to ASCII values for better understanding.

Sending getinfo SMS command via GPRS Codec13.

Hexadecimal stream:
00000000000000170D01050000000F0000016C0A81C320676574696E666F010000AAD2

Parsed:

Server Command
Server Command Part HEX Code Part
Zero Bytes 00 00 00 00
Data Size 00 00 00 17
Codec ID 0D
Command Quantity 1 01
Command Type 05
Command Size 00 00 00 07
Timestamp 00 00 01 6C 0A 81 C3 20
Command 67 65 74 69 6E 66 6F
Command Quantity 2 01
CRC-16 00 00 AA D2


Note that Server Command converted from HEX to ASCII means getinfo

Codec 14

  • About Codec14

Codec14 is original Teltonika protocol for device-server communication over GPRS messages and it is based on Codec12 protocol.
Main difference of Codec14 is that, device will answer to GPRS command if device physical IMEI number matches specified IMEI number in GPRS command.

Codec14 GPRS commands can be used for sending configuration, debug, digital outputs control commands or other (special purpose command on special firmware versions).

  • FMB firmware requirements

Implemented in base firmware from FMB.Ver.03.25.04.Rev.00 and newer.

  • General Codec14 message structure

The following diagram shows basic structure of Codec14 messages.

Command message structure

0x00000000 (preamble) Data size 0x0E (Codec ID) Command quantity 0x05
(Message type)
Command size + IMEI size (8 bytes) IMEI (HEX) Command Command quantity CRC-16
4 bytes 4 bytes 1 bytes 1 bytes 1 bytes 4 bytes 8 bytes X bytes 1 bytes 4 bytes


Response message structure

0x00000000 (preamble) Data size 0x0E (Codec ID) Response quantity 0x06 / 0x11 (Message type) Response size + IMEI size (8 bytes) IMEI (HEX) Response Response quantity CRC-16
4 bytes 4 bytes 1 bytes 1 bytes 1 bytes 4 bytes 8 bytes X bytes 1 bytes 4 bytes

Preamble – the packet starts with four zero bytes.
Data Size – size is calculated from Codec ID field to the second command or response quantity field.
Codec ID – in Codec14 it is always 0x0E.
Command/Response Quantity 1 – it is ignored when parsing the message.
Type – if it is request command from server it has to contain 0x05. The response type field will contain 0x06 if it’s ACK or 0x11 if it’s nACK.
Explanation: If command message IMEI is equal to actual device IMEI, received command will be executed and response will be sent with ACK (0x06) message type field value. If command message IMEI doesn’t match actual device IMEI, received command won’t be executed and response to server will be sent with nACK (0x11) message type field value.
Command/Response Size – command or response length.
Note: make sure that size is IMEI size 8 + actual command size. Minimal value is 8 because Codec14 always contain IMEI and it’s 8 bytes.
IMEI (HEX) – it is send as HEX value. Example if device IMEI is 123456789123456 then IMEI data field will contain 0x0123456789123456 value.
Command/Response – command or response in HEX.
Command/Response Quantity 2 - a byte which defines how many records (commands or responses) is in the packet. This byte will not be parsed but it’s recommended that it should contain same value as Command/Response Quantity 1.
CRC-16 - calculated from Codec ID to the Command/Response Quantity 2. CRC (Cyclic Redundancy Check) is an error-detecting code using for detect accidental changes to RAW data. For calculation we are using CRC-16/IBM. More information about it you can found here.

  • GPRS in Codec14 examples

Hexadecimal stream of GPRS command and answer in this example are given in hexadecimal form. The different fields of message are seperate into different table columns for better readability and some of them are coverted to ASCII values for better understanding.

Sending getver SMS command via GPRS Codec14:

Server requests in Hexadecimal stream:
00000000000000160E01050000000E0352093081452251676574766572010000D2C1

Parsed:

Server Command
Server Command Part HEX Code Part
Zero Bytes 00 00 00 00
Data Size 00 00 00 16
Codec ID 0E
Command Quantity 1 01
Command Type 05
Command Size 00 00 00 0E
IMEI 00 00 00 0E
Command 03 52 09 30 81 45 22 51
Command Quantity 2 01
CRC-16 00 00 D2 C1


Note that Server Command converted from HEX to ASCII means getver

Device ACK response in hexadecimal stream:
00000000000000AB0E0106000000A303520930814522515665723A30332E31382E31345F3034204750533A41584E5F352E31305F333333332048773A464D42313230 204D6F643A313520494D45493A33353230393330383134353232353120496E69743A323031382D31312D323220373A313320557074696D653A3137323334204D4143 3A363042444430303136323631205350433A312830292041584C3A30204F42443A3020424C3A312E362042543A340100007AAE

Parsed:

Device Answer
Device Answer Part HEX Code Part
Zero Bytes 00 00 00 00
Data Size 00 00 00 37
Codec ID 0E
Response Quantity 1 01
Response Type 06
Response Size 00 00 00 A3
IMEI 03 52 09 30 81 45 22 51
Response 56 65 72 3A 30 33 2E 31 38 2E 31 34 5F 30 34 20 47 50 53 3A 41 58 4E 5F 35 2E 31 30 5F 33 33 33 33 20 48 77 3A 46 4D 42 31 32 30 20 4D 6F 64 3A 31 35 20 49 4D 45 49 3A 33 35 32 30 39 33 30 38 31 34 35 32 32 35 31 20 49 6E 69 74 3A 32 30 31 38 2D 31 31 2D 32 32 20 37 3A 31 33 20 55 70 74 69 6D 65 3A 31 37 32 33 34 20 4D 41 43 3A 36 30 42 44 44 30 30 31 36 32 36 31 20 53 50 43 3A 31 28 30 29 20 41 58 4C 3A 30 20 4F 42 44 3A 30 20 42 4C 3A 31 2E 36 20 42 54 3A 34
Response Quantity 2 01
CRC-16 00 00 7A AE


Note that Device Response converted from HEX to ASCII means:
Ver:03.18.14_04 GPS:AXN_5.10_3333 Hw:FMB120 Mod:15 IMEI:352093081452251 Init:2018-11-22 7:13 Uptime:17234 MAC:60BDD0016261 SPC:1(0) AXL:0 OBD:0 BL:1.6 BT:4

Device nACK response in hexadecimal stream:
00000000000000100E011100000008035209308145246801000032AC

Parsed:

Device Answer
Device Answer Part HEX Code Part
Zero Bytes 00 00 00 00
Data Size 00 00 00 10
Codec ID 0E
Response Quantity 1 01
Response Type 11
Response Size 00 00 00 08
IMEI 03 52 09 30 81 45 24 68
Response Quantity 2 01
CRC-16 00 00 32 AC



Differences between Codec 12, Codec 13 and Codec 14

In the table below you will see differences between Codec12, Codec13 and Codec14.

Codec12 Codec13 Codec14
Communication Server - Device Communication One-way (Device -> Server communication) Server - Device Communication
Codec ID 0x0C 0x0D 0x0E
Response Message Type 0x06 - 0x06 (if it is ACK) or 0x11 (if it is nACK)
Command / Response size Only Command/Response Only Command Command/Response + IMEI
Timestamp Not Using Is Using Not Using
IMEI Not Using Not Using Is Using



24 Position SMS Data Protocol

24-hour SMS is usually sent once every day and contains GPS data of last 24 hours. TP-DCS field of this SMS should indicate that message contains 8-bit data (i.e. TP-DCS can be 0x04).
Note, that 24 position data protocol is used only with subscribed SMS. Event SMS use standard AVL data protocol.

  • Encoding

To be able to compress 24 GPS data entries into one SMS (140 octets), the data is encoded extensively using bit fields. Data packet can be interpreted as a bit stream, where all bits are numbered as follows:

Byte 1 Byte 2 Byte 3 Byte 4 ...
Bits 0 - 7 Bits 8 - 15 Bits 16 - 24 Bits 25 - ...


Bits in a byte are numbered starting from least significant bit. A field of 25 bits would consist of bits 0 to 24 where 0 is the least significant bit and bit 24 – most significant bit.

  • Structure

Below in the tables you will see SMS Data Structure:

SMS Data Structure
8 Codec ID Codec ID = 4 (0x04)
35 Timestamp Time corresponding to the first (oldest) GPS data element, represented in seconds elapsed from 2000.01.01 00:00 EET.
5 ElementCount Number of GPS data elements


SMS Data Structure
ElementCount * GPSDataElement GPS data elements
Byte - align padding Padding bits to align to 8 - bits boundary represented in seconds elapsed from 2000.01.01 00:00 EET.
64 IMEI IMEI of sending device as 8 byte long integer


The time of only the first GPS data element is specified in Timestamp field. Time corresponding to each further element can be computed as elementTime = Timestamp + (1 hour * elementNumber).

GPS Data Element
Size (bits) Field Description
1 ValidElement ValidElement = 1 – there is a valid Gps Data Element following,

ValidElement = 0 – no element at this position

ValidElement == 1 1 DifferentialCoords Format of following data
DifferentialCoords == 1 14 LongitudeDiff Difference from previous element‘s longitude.

LongitudeDiff = prevLongitude – Longitude + 213 – 1

14 LatitudeDiff Difference from previous element‘s latitude

LatitudeDiff = prevLatitude – Latitude + 213 – 1

DifferentialCoords == 0 21 Longitude Longitude = {(LongDegMult + 18 * 108) * (221 – 1)} over {36*108}
20 Latitude Latitude = (LatDegMult + 9*108) * (220 – 1) over {18*108}
8 Speed Speed in km/h

Longitude - longitude field value of GPSDataElement
Latitude - latitude field value of GPSDataElement
LongDegMult - longitude in degrees multiplied by 107 (integer part)
LatDegMult - latitude in degrees multiplied by 107 (integer part)
prevLongitude - longitude field value of previous GPSDataElemen
prevLatitude - latitude field value of previous GPSDataElement

  • Decoding GPS position

When decoding GPS data with DifferentialCoords = 1, Latitude and Longitude values can be computed as follows: Longitude = prevLongitude – LongitudeDiff + 213 – 1, Latitude = prevLatitude – LatitudeDiff + 213 – 1.
If there were no previous non-differential positions, differential coordinates should be computed assuming prevLongitude = prevLatitude = 0.
When Longitude and Latitude values are known, longitude and latitude representation in degrees can be computed as follows:

24SMS.png

  • SMS Events

When Configured to generate SMS event user will get this SMS upon event:
<Year/Month/Day> <Hour:Minute:Second> P:<profile_nr> <SMS Text> Val:<Event Value> Lon:<longitude> Lat:<latitude> Q:<HDOP>

Example:
2016./04/11 12:00:00 P:3 Digital Input 1 Val:1 Lon:51.12258 Lat: 25.7461 Q:0.6

Sending data using SMS

This type data sending is using for FMBXXX devices which can be cofigured in SMS Data Sending settings. More information about this feature you will find here.

  • Data sending via SMS

AVL data or events can be sent encapsulated in binary SMS. TP-DCS field of these SMS should indicate that message contains 8-bit data (for example: TP-DCS can be 0x04).

SMS data (TP-UD)
AVL data array IMEI
X bytes 8 bytes

AVL data array – array of encoded AVL data.
IMEI – IMEI of sending module encoded as a big endian 8 byte long number.

CRC-16

CRC (Cyclic Redundancy Check) is an error-detecting code using for detect accidental changes to RAW data. The algorithm how to calculate CRC-16 (also known as CRC-16/IBM) you will find below.
CRC16.png