STH-DCSG
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SER
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S
M
ANUAL
©
2005
V
IDERE
D
ESIGN
13
5 IEEE 1394 Interface
Digital image information is transferred from the STH-DCSG/-C to the host
PC via a 1394 cable. The cable sends a video stream from the imagers to
the PC, and sends commands from the PC to the stereo head to control
exposure, subsampling, etc. The cable also supplies power to the stereo
head.
5.1 IEEE 1394 Cable
The STH-DCSG/-C must be connected to the host PC via a 6-pin male-
male IEEE 1394 cable. The maximum length for such a cable is 4.5 m
(about 15 feet). The cable supplies both signals and power to the stereo
head. The port on the STH-DCSG is recessed, so that the IEEE 1394 cable
plug will not stick out from the camera.
The distance between the stereo head and the PC can be extended by using
a 1394 repeater.
Several 1394-enabled devices can be connected together, as long as the
connection topology doesn’t have any loops. The STH-DCSG/-C can be
connected at any point in such a topology. At a maximum, it will need
about 60% of the bandwidth of a 400 MBps connection.
5.2 IEEE 1394 Host Interface
The host computer must have an available 1394 port. Some portables and
desktops come with built-in ports. If these are 6-pin ports, they can be
connected directly to the STH-DCSG/-C. Sony laptops also support an
alternative 4-pin 1394 cabling, which has the signal pins but no power.
There are adapters that convert from 4-pin to 6-pin styles; these adapters
use an external power supply transformer.
If the host PC doesn’t have a built-in 1394 port, one can be added by
installing a 1394 PCI card or PCMCIA card for laptops. 1394 PCI cards
have 6-pin ports, and supply power. PCMCIA cards do not have the
capability of supplying power, and come with an adapter for supplying
power to the 1394 cable through a wall transformer.
Any 1394 card is suitable, as long as it conforms to OHCI (open host
controller interface) specifications. All current cards do, but some older
cards may not.
5.3 Supplying
Power
Power to the STH-DCSG is supplied through the IEEE 1394 cable. The
IEEE 1394 system must supply this power, about 1 Watt.
There are two typical PC systems: desktops and laptops.
•
Desktop PCs have either a built-in IEEE 1394 port, or a PCI card with
IEEE 1394 ports. In both cases, the desktop should supplysufficient
power to run the STH-DCSG.
•
Laptop PCs have either a built-in IEEE 1394 port, or a plug-in PC Card
(sometimes called a PCMCIA card) with several IEEE 1394 ports. In
both cases, the laptop does
not
supply power to the IEEE 1394 bus,
and a source of external power must be used – see below.
External power to the IEEE 1394 bus must have the following
characteristics:
7 to 16 VDC, > 1.5 W
The IEEE 1394 spec allows up to 40 VDC on the bus, but in practice many
devices such as PC Cards will fail if a voltage higher than 16 VDC or so is
used. We recommend using a 12 VDC source.
Power can be supplied to the bus through an IEEE 1394 hub or PC Card
with an external port. Most hubs have such a port; most PC Cards do not.
The PC Card supplied by Videre has a power port.
The format of the power plug can vary with the hub or PC Card, so please
check the specifications for the device. Generally, the positive terminal of
the plug is on the inside, and the negative is the outside cylinder.
