RUT955 GPS Protocols

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RUT955 GPS DATA PROTOCOL

AVL data array


Because the smallest information amount that can be written is one bit, there can be some bits left unused when result is byte array. Any unused bits should be left blank.

Codec ID Number of Data Data Number of Data
1 Byte 1 Byte ... 1 byte

Number of data – number of encoded data (number of records). In RUT955 codec ID is 08

Data


AVL Data ... AVL Data

AVL data – encoded data element.

AVL Data


Timestamp Priority GPS Element IO Element
8 Bytes 1 Byte 15 Bytes ...

Timestamp – difference, in milliseconds, between the current time and midnight, January 1, 1970 UTC.

Priority


0 low
1 High
2 Panic
3 Security

GPS Element


Longitude Latitude Altitude Angle Satellites Speed
4 Bytes 4 Bytes 2 Bytes 2 Bytes 1 Byte 2 Bytes
X            Longitude
Y            Latitude
Altitude     In meters above sea level
Angle	      In degrees, 0 is north, increasing clock-wise 
Satellites   Number of visible satellites
Speed	      In km/h. 0x0000 if GPS data is invalid

Longitude and latitude are integer values built from degrees, minutes, seconds and milliseconds by formula:

Gps element formula.png

d	      Degrees
m	      Minutes
s 	      Seconds
ms	      Milliseconds
p 	      Precision (10000000)

If longitude is in west or latitude in south, multiply result by –1. 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

Convered to DEC: 547146368

For more information see two‘s compliment arithmetics.

I/O Element


I/O elements (sent to server only if enabled)
Property ID Property Name Bytes IO Element
1 Digital Input Status 1 1 Logic: 0/1
2 Digital Input Status 2 1 Logic: 0/1
9 Analog Input 1 2 Voltage: mV, 0 - 30 V
21 GSM level 1 GSM signal level value in scale 1 - 5

Example


Received data: 
08040000015C1A473FC0000E3BD4A520B53DC300570167070000000403020101001504010
9158500000000015C1A475348000E3BD4AE20B53DC0005701670800000004030201010015
040109158500000000015C1A4766D0000E3BD4AE20B53DBF0057016708000000040302010
10015040109158500000000015C1A477A58000E3BD4B120B53DBD00570167080000000403
02010100150401091585000004
08 – Codec ID
           04 - Number of Data (4 records)
                       1st record data
                           0000015C1A473FC0 – Timestamp in milliseconds (1495089496000 → 1495089496,000 in Unix Timestamp = 18 May 2017 06:38:16 UTC)
                           00 – Priority
                           GPS Element
                           0E3BD4A5 – Longitude 23.8802085 = 23.8802085 º N
                           20B53DC3 – Latitude 54.8748739 = 54.8748739 º E
                           0057 – Altitude 87 meters
                           0167 – Angle 359º
                           07 – 7 Visible satellites
                           0000 – 0 km/h speed
                           I/O Element
                           00 – IO element ID of Event generated (in this case when 00 – data generated not on event)
                           04 – 4 IO elements in record
                           03 – 3 IO elements, which length is 1 Byte
                           02 – IO element ID = 02
                           01 – 2’nd IO element’s value = 1
                           01 – IO element ID = 01
                           00 – 1’st IO element’s value = 0 
                           15 – IO element ID = 21
                           04 – 21’nd IO element’s value = 4
                           01 – 1 IO element, which value length is 2 Bytes
                           09 – 1 IO element ID = 09
                           1585 – 9’th IO element’s value = 5509
                           00 – 0 IO elements, which value length is 4 Bytes
                           00 – 0 IO elements, which value length is 8 Bytes
                           2’nd record data
0000015C1A475348000E3BD4AE20B53DC000570167080000000403020101001504010915850000
                           3’d record data
0000015C1A4766D0000E3BD4AE20B53DBF00570167080000000403020101001504010915850000
                           4’th record data
0000015C1A477A58000E3BD4B120B53DBD00570167080000000403020101001504010915850000
           04 – Number of Data (4 records)

Sending data over TCP/IP

AVL data packet


AVL packet is used to encapsulate AVL data and send it to server.

Four zeros Data length Data CRC
Four zeros	 Four zero bytes (0x00)
Data length	 Number of bytes in data field (Integer)
Data		 Any AVL data array
CRC		 16bit CRC value of data (Integer). Polynomial 0xA001.

Communication with server


First when module connects to server, module sends its IMEI. IMEI is sent the same way as encoding barcode. First comes short identifying number of bytes written and then goes IMEI as text (bytes).

For example IMEI 123456789012345 would be sent as 000F313233343536373839303132333435.

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.

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:

000F313233343536373839303132333435

Server accepts the module:

01

Module sends data packet:

AVL data packet header AVL data array CRC
Four zero bytes, ‘AVL data array’ length – 254 CodecId – 08, NumberOfData – 2. (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

SENDING DATA OVER UDP/IP

UDP channel protocol


UDP channel is a transport layer protocol above UDP/IP to add reliability to plain UDP/IP using acknowledgment packets. The packet structure is as follows:

UDP datagram
UDP channel packet x N
Packet length 2 bytes Packet length (excluding this field) in big endian byte order
Packet Id 2 bytes Packet id unique for this channel
Packet type 1 byte Type of this packet
Packet payload m bytes Data payload
Packet Type
1 Data packet requiring acknowledgment

Acknowledgment packet should have the same packet id as acknowledged data packet and empty data payload. Acknowledgement should be sent in binary format.

Acknowledgement packet
Packet length 2 bytes 0x0003
Packet id 2 bytes The same as in acknowledged packet
Packet type 1 byte 0x01

Sending AVL data using UDP channel


AVL data is sent encapsulated in UDP channel packets (Data payload field).

AVL data encapsulated in UDP channel packet
AVL packet id (1 byte) Module IMEI AVL data array
AVL packet id (1 byte)    id identifying this AVL packet 
Module IMEI               IMEI of a sending module encoded the same as with TCP
AVL data array            array of encoded AVL data
Server response to AVL data packet
AVL packet id (1 byte) Number of accepted AVL elements (1 byte)

AVL packet id (1 byte) – id of received AVL data packet

Number of AVL data elements accepted (1 byte) – number of AVL data array entries from the beginning of array, which were accepted by the server.

Scenario:

Module sends UDP channel packet with encapsulated AVL data packet (Packet type=1).

Server sends UDP channel packet with encapsulated response (Packet type=1).

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
Len – 253,

Id – 0xCAFE,

Packet type – 01

AVL packet id – 0xDD,

IMEI – 1234567890123456

CodecId – 08,

NumberOfData – 2. (Encoded using continuous bit stream)

00FDCAFE01 DD000F3133343536373839303132333435 0802(data elements)02

Server must respond with acknowledgment:

UDP channel header AVL packet acknowledgement
Len – 5,

Id – 0xCAFE,

Packet type – 01

AVL packet id – 0xDD,

NumberOfAcceptedData – 2

0005CAFE01 DD02