Garmin GPS 16HVS Instruction Manual - Page 13
Appendix A., CR23X/CR10X Programs
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Appendix A. CR23X/CR10X Programs A.1 Programming Program instruction 15 (P15) is used to read the NEMA $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 nonnumeric 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 NEMA $GPGGA Data String Parameter 1 2 3 4 5 6 7 8 9 10 11 12 Data 1 61 -- 1 05 1 0 42 100 80 1 1 0 Description Repetitions 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 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