Measurement Computing LogBook Series - Manual (Page 92)

6-4 GPS and Serial Device Data Collection 958396 LogBook User’s Manual
Configuring an Acquisition
What you need to know about your non-GPS device
To successfully capture data sourced by a non-GPS device, you’ll need intimate operational knowledge about the
device. Use the Operator’s Manual shipped with the device to collect information about the following:
Baud rate, parity,
stop bits, and data
bits To successfully communicate with the serial device, the LogBook’s serial port(s)
must be set up to match the RS-232 parameters of the serial device.
Data transmission
rate Typically, serial devices send a block of ASCII data or an ASCII sentence
(terminated by CR LF) on a periodic basis—once per second, for example. Knowing
this rate will allow you to set up your sample rate for the serial channel(s)
intelligently. To capture every value transmitted by the serial device, set the sample
rate for the serial channel at about twice the rate of the serial data transmission rate.
Data string To successfully parse and convert fields within the serial data string, complete
knowledge of the string format must be known. For each serial channel, a format
string must be created which perfectly describes the expected message. The
Windows’ Hyperterminal application is sometimes helpful for inspecting the serial
strings sourced by a device.
What you need to know about your GPS
The LogBook has direct support for all GPSs that conform to the NMEA 0183 protocol. A GPS of this
kind can be connected and operated without any knowledge of the communication or protocol parameters.
The included GPS support makes use of the NMEA 0183’s GGA message, yielding Longitude, Latitude,
Altitude, UTC time, and Quality of fix.
If additional GPS parameters are desired, serial channels can be defined to capture them, just like
parameters from general, non-GPS devices. To maximize flexibility, user-defined serial channels and pre-
defined GPS channels can be used concurrently on the same GPS device. For example, the GPS Longitude
channel can be enabled concurrently with a user-defined serial channel that captures the heading data from
the same GPS.
To capture user-defined parameters from the GPS, intimate knowledge of the GPS data strings is required.