
ZENO
®
-3200 USER MANUAL
Coastal Environmental Systems (206) 682-6048
Page 156
NMEA 0183: this interface protocol was created by the National Marine Electronics Association.
Originally established to allow marine navigational equipment to share information, NMEA 0183 is a
simple but comprehensive ASCII protocol that defines both the communications interface and data
format.
175
NMEA 0183 messages can be polled or asynchronous.
SDI-12: the acronym stands for Serial Data Interface at 1200 baud. It was created by a group of
serial sensor company representatives and programmers to create a standard communications protocol
between intelligent sensors and data records.
176
All SDI-12 messages are polled.
CCSAIL Communications Protocol: was created by Coastal Environmental Systems.
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CCSAIL
messages can be polled or asynchronous.
Proprietary: any message format that does not conform to any known standard format and includes
both polled and asynchronous messages.
Information specific to each sensor type is listed in the next table:
Sensor Type
Code
(Line Item #1)
Name
Polled or
Asynch.
Message
Format
Time Per
Measurement
11 Serial Compass P 600 ms
15 GPS Receiver A
NMEA
Up to 5 s
12 CCSAIL Sensor P Up to 4 s
19 Asynchronous CCSAIL Sensor A
CCSAIL
N/A
16 General Serial Script Sensor (USI ) Both Any
Depends upon Script
Definition
13 SDI-12 Sensor
18 Concurrent SDI-12 Sensor
2 s Minimum, Depends
upon Sensor.
17 Continuous SDI-12 Sensor
P SDI-12
Up to 2 s
10.3.4. Specifics for Each Supported Serial Sensor Type
Serial Compass Specifics
The Serial Compass sensor type was designed around the Navico Serial Compass. Its measurement range
is 0 to 360 degrees from true North with 0.1 degree resolution. It uses NMEA messages transmitted at
4800 baud on TTL. It is usually connected to the ZENO
®
-3200 via the COMPASS interface located on
the ZENO
®
-3200 CPU board.
A typical NMEA serial compass message looks something like this:
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Each NMEA 0183 message starts with a "$", a two letter "talker ID", a three letter "sentence ID", followed by a
number of data fields separated by commas, an asterisk "*", an optional checksum, and a carriage return/line feed
combination. The checksum is calculated by exclusive-oring all of the characters between the "$" and "*"
characters. Total message length is restricted to 82 characters. Information about NMEA is available at their
website: http://www.nmea.org/
.
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More information, including a complete description of SDI-12, is available from the SDI-12 Support Group's
website at http://www.sdi-12.org/
.
177
Refer to Section 4.6.
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