PTU-D46 User’s Manual (v2.14.0) PTU OPTIONS
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6 PTU OPTIONS
6.1 EIO Option: Expansion Serial Ports and Control
In many cases, other serial devices are attached or proximal to the pan-tilt. In these cases, you
can directly connect these other devices to your host computer serial ports. Doing this requires
more serial ports on your host computer, and additional serial cabling is required. To reduce the
host computer port and cabling requirements, an option for the PTU Controller is provided which
adds two additional serial ports to the PTU controller.
A mouse or trackball can be connected to one of the expanded serial ports to allow direct user
control of pan-tilt position without requiring an external host computer.
A PTU controller with additional serial ports may be identified by the two DB9 male
connectors on the controller housing, and the firmware version number will include a “/D” (see
Section 4.5.5 for querying PTU firmware). These additional RS232C DTE ports are designated
Channel A (CHA) and Channel B (CHB).
The serial port expansion channels are controlled from the main PTU controller serial port.
CHA/CHB RS232C ports may be configured from the PTU controller serial port to set expanded
port baud rate, data bits, parity, and handshaking. Each channel operates independently, and the
PTU controller fully buffers bi-directional data flow to allow for communications rate mismatch.
Point-to-point communications between the PTU controller serial port and an expansion channel
(e.g., CHB) is initiated by the host computer. Point-to-point communications is broken upon
command from the host computer.
Communications from a serial device attached to an expansion serial channel is buffered (at
least 200 characters). When hardware handshaking is not used, this buffer can overflow, so care
should be taken to ensure that attached devices do not exceed the buffer size before its data on the
serial channel is read by the host computer.
6.1.1 Select Serial Communications Target
Description
Command establishes point-to-point communications between the host
computer connected to the PTU controller serial port and the expanded serial
port (CHA/ CHB) or pan-tilt controller. When an expansion port channel is
selected, the host computer is no longer communicating with the PTU
controller, but instead with the external device connected to the expanded
serial port. To resume communicating with the PTU controller, the host
computer need only issue a command selecting the PTU controller as its
desired communications target.
The baud rate of an expansion port does not affect the communications
with the serial port connecting the host computer to the pan-tilt controller
(which defaults to 9600 baud).
Syntax
Establish communications with CHA: @A<delim>
Establish communications with CHB: @B<delim>
Resume communications with the PTU controller: @<delim>
The modified commands below ensure that <# raw bytes> bytes will be
passed directly from the host computer to the expanded serial port without
any attempt to change the communications target. This allows strings like
@B
to be embedded in communications between the host computer and the
expanded serial port device, without causing communications between the
two to be inadvertently interrupted.
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