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How the Polaris Vicra System Works
3.15
Data Transmission Rate
The Polaris Vicra System can achieve an internal tool transformation update rate of 20 Hz. The host
update rate (the rate at which the host computer receives data) is dependent on the following factors:
Baud Rate The baud rate specifies how fast data is transferred from the system to the host computer.
At lower baud rates, the host computer may not receive tool transformations at 20 Hz.
API command reply length The more data the system must return with every transformation, the
slower the host update rate. The amount of data returned with each transformation increases as you
track more tools and select more options.
Application speed The host transmission rate can vary according to how often the application asks
for data, and how often the graphical user interface (in particular, graphics) need to be updated.
3.16
Serial Port Emulation
The Host USB Converter emulates a standard PC serial port, such that the host application may
communicate with the Polaris Vicra System as if it was a standard RS-232 device. A feature of this
is that the following modem status bits are used as follows:
•
The Data Set Ready (DSR) will be set when the Host USB Converter senses that a Position
Sensor is connected (power must also be connected to the Host USB converter).
•
The Ring Indicator (RI) will be set when a fault condition is showing on the Host USB
Converter error indicator.
If your operating system cannot set the serial port rate directly to 1.2 Mbaud, an aliased 19200 baud
rate is provided to enable you to run at the higher speed. Do not use the COMM API command's
baud rate selection of "2" (in this case COMM 2xxxx) but instead use a selection of "7" (COMM
7xxxx).
40
Amount of Light
Passing Through
Lenses to CCDs
90 %
800 nm
880 nm
Figure 3-9 Filter Spectral Response
Amount of Light
Detected by CCDs
Light Wavelength
Polaris Vicra User Guide - Revision 2
1100 nm
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