Vinten Radamec Free-d - Manual (Page 28)

Vinten Broadcast Ltd free - d ™ Installation Manual V1.4.4
Page 28 of 46
Appendix A, free-d
™
communications protocol v1.0
A.1 General
Communications with the free-d™ unit use RS422/RS485 serial data as follows:
Baud rate: 38.4 kbaud
Data bits: 8 (LSB first)
Parity: Odd
Stop bits: 1
Total bits: 11
Data is transferred in messages. Each message consists of:
Message type
Camera ID number
Data (depending on message type)
Checksum
Multi-byte data values are sent most-significant-byte first.
The checksum is calculated by subtracting (modulo 256) each byte of the
message, including the message type, from 40 (hex).
The Camera ID number identifies the camera concerned. If the Camera ID of
a message received by the
free-d™ unit does not match that of the camera to
which the unit is connected, the message is ignored. However, if the Camera
ID is set to FF (hex) no comparison is made and the message is always
recognised. Messages transmitted by the
free-d™ unit carry the ID number of
the camera to which it is connected.
A.2 Protocols
There are two modes of operation, stream mode and polled mode. In stream
mode, the
free-d™ unit will send position updates continuously at an
approximate rate of 30 per second. In polled mode, the free-d™ unit will send a
message only when specifically requested - a maximum rate of 100 polls per
second is allowed. Switching between the two modes is possible using a
command message.
The free-d™ unit initialises itself to a ‘Radamec-compatible’ stream mode, in
which it transmits messages with the same format as would be returned by a
robotic pedestal. Since Radamec-format messages have no provision for a
camera ‘roll’ value, in this mode the camera must be mounted on a tripod or
other suitable platform.