Francis Searchlights Voyager 2 User Instruction & Installation Manual page 21

DATA_TILT_POSITION (Hex 19)
This is a three-byte command. Following the DATA_TILT_POSITION com-
mand two data bytes specify the position to which the lamp must move. The
bearing resolution is 0.1 degrees. The value is sent LSB first with the first byte
representing the lower position command bits. The MSB (sent last) lower 4
bits represents the remaining value. The position value is centred on 2048
(Binary 1000 0000 0000) so a value of 2048 would make the lamp move to
the dead ahead position. An increasing value represents tilting up with a reso-
lution of 0.1 degrees. A value of 2058 would therefore represent 1 degree up
from dead ahead (2058 = 2048 + 10 – but resolution is 0.1 degrees so a value
10 = 1 degree). Values below 2048 represent tilting down so a value of 1748
would represent an angle 30 degrees down from centre.
LAMP TRANSMITTED DATA
A given lamp after it receives its normal address (Hex 110 to Hex 138) will al-
ways send the following data in this specific order. The lamp must transmit its
first data byte (pan position) within 1mS of receiving its standard address and
the gaps between successive bytes must be less than 1mS.
Lamp TX Byte 1 – Pan position LSB
Lamp TX Byte 2 – Pan position MSB
Lamp TX Byte 3 – Tilt position LSB
Lamp TX Byte 4 – Tilt position MSB
Lamp TX Byte 5 – Lamp status
Lamp TX Byte 6 – CRC
Each byte is described below
Pan Position
This is a 12-bit value with lamp pointing straight ahead being a value of 2048
and the value increasing as the lamp rotates clockwise as viewed from above.
The system has a resolution of 0.1 degrees so 90 degrees clockwise from
centre would be a value of 2948 (2048 + 900).
Tilt position
This is a 12-bit value with lamp horizontal being a value of 2048 and the value
increasing as the lamp beam points up. This has a resolution of 0.1 degrees.
Lamp Status
This is an 8-bit value with each bit representing a specific status aspect. The
bit functions are listed below; -
Bit 0 - Lamp on
Bit 1 - Pan Limit reached
Bit 2 - Tilt Limit reached
Bit 3 - Lamp Recording
Bit 4 - Lamp Playing
Bit 5 - Lamp Overheated
Bit 6 - Lamp moving to home
Bit 7 - Reserved
The bits are all true logic so if the lamp is switched on, bit 0 will be high.