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https://github.com/tinygo-org/drivers.git
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gps: improvements and bugfixes (#186)
* gps: buxfixes and refactoring of API to separate device from parser Signed-off-by: deadprogram <ron@hybridgroup.com> * gps: simplify time parser Signed-off-by: deadprogram <ron@hybridgroup.com> * gps: add support for RMC sentences Signed-off-by: deadprogram <ron@hybridgroup.com> * gps: small renaming to remove reduntant use of word GPS Signed-off-by: deadprogram <ron@hybridgroup.com>
This commit is contained in:
Ron Evans
GitHub
+94
-63
@@ -1,92 +1,123 @@
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package gps
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import (
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"errors"
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"strconv"
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"strings"
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"time"
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)
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type GPSParser struct {
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gpsDevice GPSDevice
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var (
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errEmptyNMEASentence = errors.New("cannot parse empty NMEA sentence")
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errUnknownNMEASentence = errors.New("unsupported NMEA sentence type")
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errInvalidGGASentence = errors.New("invalid GGA NMEA sentence")
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errInvalidRMCSentence = errors.New("invalid RMC NMEA sentence")
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)
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// Parser for GPS NMEA sentences.
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type Parser struct {
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}
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// fix is a GPS location fix
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// Fix is a GPS location fix
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type Fix struct {
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Valid bool
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Time time.Time
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Latitude float32
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Longitude float32
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Altitude int32
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// Valid if the fix was valid.
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Valid bool
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// Time that the fix was taken, in UTC time.
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Time time.Time
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// Latitude is the decimal latitude. Negative numbers indicate S.
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Latitude float32
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// Longitude is the decimal longitude. Negative numbers indicate E.
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Longitude float32
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// Altitude is only returned for GGA sentences.
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Altitude int32
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// Satellites is the number of visible satellites, but is only returned for GGA sentences.
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Satellites int16
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}
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func Parser(gpsDevice GPSDevice) GPSParser {
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return GPSParser{
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gpsDevice: gpsDevice,
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// NewParser returns a GPS NMEA Parser.
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func NewParser() Parser {
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return Parser{}
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}
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// Parse parses a NMEA sentence looking for fix info.
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func (parser *Parser) Parse(sentence string) (fix Fix, err error) {
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if sentence == "" {
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err = errEmptyNMEASentence
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return
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}
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}
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// NextFix returns the next GPS location Fix from the GPS device
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func (parser *GPSParser) NextFix() (fix Fix) {
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var ggaSentence = nextGGA(parser.gpsDevice)
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var ggaFields = strings.Split(ggaSentence, ",")
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fix.Altitude = findAltitude(ggaFields)
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fix.Satellites = findSatellites(ggaFields)
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fix.Longitude = findLongitude(ggaFields)
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fix.Latitude = findLatitude(ggaFields)
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fix.Time = findTime(ggaFields)
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fix.Valid = (fix.Altitude != -99999) && (fix.Satellites > 0)
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return fix
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}
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// nextGGA returns the next GGA type sentence from the GPS device
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// $--GGA,,,,,,,,,,,,,,*hh
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func nextGGA(gpsDevice GPSDevice) (sentence string) {
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for {
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sentence = gpsDevice.NextSentence()
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if sentence[3:6] == "GGA" {
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return sentence
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typ := sentence[3:6]
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switch typ {
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case "GGA":
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fields := strings.Split(sentence, ",")
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if len(fields) != 15 {
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err = errInvalidGGASentence
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return
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}
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fix.Altitude = findAltitude(fields[9])
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fix.Satellites = findSatellites(fields[7])
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fix.Longitude = findLongitude(fields[4], fields[5])
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fix.Latitude = findLatitude(fields[2], fields[3])
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fix.Time = findTime(fields[1])
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fix.Valid = (fix.Altitude != -99999) && (fix.Satellites > 0)
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case "RMC":
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fields := strings.Split(sentence, ",")
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if len(fields) != 13 {
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err = errInvalidRMCSentence
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return
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}
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fix.Longitude = findLongitude(fields[5], fields[6])
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fix.Latitude = findLatitude(fields[3], fields[4])
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fix.Time = findTime(fields[1])
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fix.Valid = (len(fields[2]) > 0 && fields[2][0:1] == "A")
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default:
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err = errUnknownNMEASentence
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}
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return
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}
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// findTime returns the time from a GGA sentence:
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// findTime returns the time from an NMEA sentence:
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// $--GGA,hhmmss.ss,,,,,,,,,,,,,*xx
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func findTime(ggaFields []string) time.Time {
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if len(ggaFields) < 1 || len(ggaFields[1]) < 6 {
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func findTime(val string) time.Time {
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if len(val) < 6 {
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return time.Time{}
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}
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ts := strings.Builder{}
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ts.WriteString(ggaFields[1][0:2])
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ts.WriteString(":")
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ts.WriteString(ggaFields[1][2:4])
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ts.WriteString(":")
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ts.WriteString(ggaFields[1][4:6])
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var t, _ = time.Parse("15:04:05", ts.String())
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h, _ := strconv.ParseInt(val[0:2], 10, 8)
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m, _ := strconv.ParseInt(val[2:4], 10, 8)
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s, _ := strconv.ParseInt(val[4:6], 10, 8)
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ms, _ := strconv.ParseInt(val[7:10], 10, 16)
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t := time.Date(0, 0, 0, int(h), int(m), int(s), int(ms), time.UTC)
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return t
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}
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// findAltitude returns the altitude from a GGA sentence:
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// findAltitude returns the altitude from an NMEA sentence:
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// $--GGA,,,,,,,,,25.8,,,,,*63
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func findAltitude(ggaFields []string) int32 {
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if len(ggaFields) > 8 && len(ggaFields[9]) > 0 {
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var v, _ = strconv.ParseFloat(ggaFields[9], 32)
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func findAltitude(val string) int32 {
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if len(val) > 0 {
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var v, _ = strconv.ParseFloat(val, 32)
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return int32(v)
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}
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return -99999
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}
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// findLatitude returns the Latitude from a GGA sentence:
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// findLatitude returns the Latitude from an NMEA sentence:
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// $--GGA,,ddmm.mmmmm,x,,,,,,,,,,,*hh
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func findLatitude(ggaFields []string) float32 {
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if len(ggaFields) > 2 && len(ggaFields[2]) > 8 {
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var dd = ggaFields[2][0:2]
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var mm = ggaFields[2][2:]
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func findLatitude(val, hemi string) float32 {
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if len(val) > 8 {
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var dd = val[0:2]
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var mm = val[2:]
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var d, _ = strconv.ParseFloat(dd, 32)
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var m, _ = strconv.ParseFloat(mm, 32)
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var v = float32(d + (m / 60))
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if ggaFields[3] == "S" {
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if hemi == "S" {
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v *= -1
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}
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return v
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@@ -94,16 +125,16 @@ func findLatitude(ggaFields []string) float32 {
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return 0.0
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}
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// findLatitude returns the longitude from a GGA sentence:
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// findLatitude returns the longitude from an NMEA sentence:
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// $--GGA,,,,dddmm.mmmmm,x,,,,,,,,,*hh
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func findLongitude(ggaFields []string) float32 {
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if len(ggaFields) > 4 && len(ggaFields[4]) > 8 {
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var ddd = ggaFields[4][0:3]
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var mm = ggaFields[4][3:]
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func findLongitude(val, hemi string) float32 {
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if len(val) > 8 {
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var ddd = val[0:3]
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var mm = val[3:]
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var d, _ = strconv.ParseFloat(ddd, 32)
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var m, _ = strconv.ParseFloat(mm, 32)
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var v = float32(d + (m / 60))
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if ggaFields[5] == "W" {
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if hemi == "W" {
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v *= -1
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}
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return v
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@@ -111,11 +142,11 @@ func findLongitude(ggaFields []string) float32 {
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return 0.0
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}
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// findSatellites returns the satellites from a GGA sentence:
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// findSatellites returns the satellites from an NMEA sentence:
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// $--GGA,,,,,,,nn,,,,,,,*hh
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func findSatellites(ggaFields []string) (n int16) {
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if len(ggaFields) > 6 && len(ggaFields[7]) > 0 {
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var nn = ggaFields[7]
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func findSatellites(val string) (n int16) {
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if len(val) > 0 {
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var nn = val
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var v, _ = strconv.ParseInt(nn, 10, 32)
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n = int16(v)
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return n
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