User`s manual

NexSens Technology, Inc.
iSIC User‟s Manual 36
2.4 NMEA 0183
NexSens iSIC data loggers support NMEA 0183 sensors connected to a data logger via RS232.
Implementation:
 RS232, baud rates 1200 to 57600 supported.
 Up to (3) messages per sensor can be configured (note: devices that output more than
three messages can be logged as more than one sensor)
 Optional checksum: if a checksum is present in the NMEA message, the iSIC will use that
checksum to determine if the message is valid. If a checksum is not present, the
checksum requirement will be ignored.
 The iSIC follows the NMEA 0183 protocol specification of 82 characters per message
(including $ sign and line feed)
 iChart will automatically arrange selected parameters according to the their message (ie
if three parameters from GGA and two parameters from VTG are selected, iChart will
group the parameters together based on the message name regardless of the message
order selected.
Additionally, there are a few data marker messages that the iSIC uses to help diagnose NMEA
0183 communication problems. These markers will be logged instead of the actual data message
in the case of error.
Note: a „primary field‟ is a field in a sentence that is to be parsed and log. A „qualifier field‟
is a second field that adds meaning to the primary field. For example, in a GCC sentence,
field 2 is lat., field 3 is either 'E' or 'W'. Field 2 is the primary field, field 3 is the qualifier
field. Another example, in DBT sentence, field 1 is the primary field, field 2 is the qualifier
field and it must be 'f' indicate field 1 unit is in feet.
Marker Messages:
1) -100002: empty primary field
2) -100004: empty qualifier field
3) -100006: invalid qualifier field
4) -100008: reach the end of a sentence
5) -100010: complete sentence is not detected.