VB20SL User Guide
Page 14 of 30
Pitch/Roll Angle Offset
It is not always possible to mount the antennas on a vehicle so that they are perfectly level. In order to compensate for a non-level antenna placement you
should use the Pitch offset facility, which will automatically compute and then use an offset compensation.
Measuring Roll angle:
To measure Roll angle accurately the antennas need to be aligned as close as possible to a line perpendicular 90
o
to the longitudinal line of the car.
Setting the Offset
Press t
he ’■’
button to enter the Main menu then select the Setup Antenna Menu, and then select the Pitch antenna setup menu.
From within either the Pitch antenna setup menu select Pitch Roll offset, when the screen shows ‘CALC OFFSET’ press the ’■’ to calculate the PITCH offset.
If required, the Pitch Angle offset can be re-
calculated at any time by repeating this procedure. Selecting the ‘Clear Offset’ option will also clear the current
offset value.
Setting Slip Angle Offset Remotely via CAN Messages
It is possible to request that the VB20SL calculates a Slip Angle Offset by sending it requests via CAN.
The CAN Baud rate is 500Kbit/s, Motorola 11 bit
– Standard Frame, The DLC = 8
The VB20SL will respond on CAN to indicate stages of the Slip offset process and also indicate completion or failure.
Please see the table below:
Message Type
CAN ID
Data Bytes
0
1
2
3
4
5
6
7
Request
Start Slip offset calculation
0x7FE
46
49
4C
45
4D
41
4E
40
Request
Cancel Slip offset calculation
0x7FE
46
49
4C
45
4D
41
4E
41
Response
Increase speed to >25kmh
0x7FB
05
02
00
00
00
00
00
00
Response
Drive Straight
0x7FB
05
03
00
00
00
00
00
00
Response
Offset done
– value shown in Data bytes 2-5
0x7FB
05
01
3F
9D
70
A4
00
00
Response
Offset failed
0x7FB
05
00
00
00
00
00
00
00
The Response message to indicate completion also contains the Offset value as a 32 bit IEEE float on Data bytes 2-5.
In the example above Data bytes 2 - 5 = 3F 9D 70 A4 which equals a decimal value of 1.23
o
