Campbell-scientific GPS16-HVS Garmin GPS Receiver Manuel d'utilisateur télécharger pdf (Page 15)

Appendix A. CR23X/CR10X Programs

A.1 Programming

Program instruction 15 (P15) is used to read the NMEA $GPGGA string of

time and position data. Each iteration of P15 can either read the numeric fields

or read everything. When reading the numeric fields, such as time, latitude,

longitude and elevation, P15 requires non-numeric delimiters between data

points. The only available format of GPS data with delimiters is the NMEA

0183 format. Program instruction 15 (P15) reads serial data and discards non-

numeric values. All non-numeric values act as delimiters between numbers,

and decimal points can also act as delimiters. P15 can be used to import

everything in the string, character by character, and convert it to the decimal

equivalent. The decimal equivalent method is seldom used, and only when the

general area (hemisphere) is not known.

A.1.1 Program Execution Interval

When the PPS signal is used to trigger the read data function (P15), the

program table execution interval does not matter. Otherwise the timing

between the Garmin16-HVS output and the datalogger read must be

considered. Generally the execution interval can not be less than 2 seconds

when the PPS signal is not used.

A.1.2 Reading GPS Data

TABLE A-1 is a sample CR23X P15 instruction for reading NMEA $GPGGA

data string. The second parameter has two dashes indicating data buffering has

been turned off. The CR10X does not have the data buffering option.

TABLE A-1. P15 for NMEA $GPGGA Data String

Parameter

Data

Description

Repetitions

61 --

Configuration code for RS232 ASCII data at 1200 baud

with data buffering turned off. The -- indicates data

buffering turned off. Decimal delimiter

Delay before sending data out

Control ports. Two digit format AB. A is for

handshaking and set to zero. B in this example is control

port 5 (datalogger RCV). Garmin16-HVS

communication cable: GPS transmit to control port 5 in

this example

Input location where first character to transmit is stored.

Note: nothing is actually transmitted

Number of consecutive input locations to send

Termination character, 42 is ASCII equivalent of the

asterisk

100

Maximum number of characters to receive.

Delay in mS. How long to wait for $GPGGA string

Starting input location for time and position data

Multiplier, always 1.

Offset, always 0.

A-1

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 31 32

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