LTI MapStar TruAngle User’s Manual 3rd Edition
Section #4 - Managing Serial Data
Page 11
Section #4 - Managing Serial Data
The TruAngle's two serial ports are used to communicate
with external devices. The one labeled LASER to an LTI
laser product and the one labeled DATA to a data collector
or PC. In normal operation, the laser’s Fire button is pressed
and data is automatically downloaded to the TruAngle. It
then fires, inserts the angle value into the data string and
automatically sends it out the DATA port. In addition,
commands can be sent from the data collector/PC to the
TruAngle or laser; such as parameter change commands
and a remote trigger command to Fire the laser
(see below). Figure #12 shows the data flow.
The cables, data collectors, and software needed for remote
operations are available from LTI or an Authorized Dealer.
NMEA Compliance
The TruAngle uses the LTI CR400 data format follows the guidelines of the NMEA 0183 Standard for
Interfacing Marine Electronic Navigational Devices, Revision 2.0:
•
NMEA 0183 provides for both standard and proprietary data formats. Since none of the standard
formats are useful for the data transferred from the Impulse, special proprietary formats are used.
Rules described in the NMEA standard governing general message structure, leading and trailing
characters, numeric values, delimiting character, checksums, maximum line length, data rate, and bit
format are followed exactly.
•
As required by NMEA 0183, the CR400-format does not respond to unrecognized header formats,
malformed messages, or messages with invalid checksums.
Laser Settings
•
Impulse 200 and 200 LR:
Select the CR400 message format and the Auto Download option.
The Impulse will not communicate with the TruAngle if the IP200 download format is active.
•
TruPulse Series:
The CR400 message format with Auto Download is only option offered
in the unit. No settings are necessary.
•
TruSpeed Sx:
Select the CR400 message format. The TruSpeed Sx will not communicate with
the TruAngle if the TruSpeed download format is active.
•
UltraLyte 200 and 200 LR:
Select the CR400 message format. The UltraLyte will not
communicate with the TruAngle if the UL200 download format is active.
Remote Triggering
It is possible to remotely trigger the TruAngle by using an external computer, data collector, or switch closure.
Remote triggering uses an open collector closure to ground or an active low TTL or RS232 level signal to the
'trigger' pin on the serial connector. It requires a special order download cable that connects the remote trigger
signal from the encoder to the 'RTS' output signal of a computer's serial port.
When using a serial cable with a remote trigger connection hard-wired, care must be taken to control the state
of the RTS signal from the host computer. Often times the default state of the RTS signal will be low, causing
an inadvertent trigger. Since the remote trigger signal is treated the same as a button press on the TruAngle,
holding the signal low is identical to holding down a button, which prevents a response to any additional
buttons that are pressed.
Figure #12