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sdk:gps-udp-client-gnsstogps [2019/07/08 13:56] fachet |
sdk:gps-udp-client-gnsstogps [2020/12/10 16:13] juraschek [SDK Script gps-udp-client-GNSStoGPS.are] |
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| + | ====== Background ====== | ||
| + | GPS was the first Global Navigation Satellite System (GNSS) and the term GPS is often used as a synonym for GNSS. | ||
| + | |||
| + | Older software often only checks for NMEA 0183 sentences starting with <nowiki>"$GP"</nowiki> (= GPS only) instead of looking for all GNSS systems. | ||
| + | |||
| + | Newer GNSS receivers often use multiple GNSS systems and therefore <nowiki>"$GN"</nowiki> is used (<nowiki>"$GNRMC..."</nowiki>) if it recives a combination of GPS, Galileo and GLONASS signals. | ||
| + | |||
| + | It would be better to us instead of <nowiki>"$GPRMC"</nowiki> either <nowiki>"$G.RMC"</nowiki> ("." = anychar) for using GPS, Galileo and/or GLONASS (GNSS) or even <nowiki>"$..RMC"</nowiki> which means any source. | ||
| + | |||
| + | <code> | ||
| + | NMEA 0183 sentence "$XXYYY..." explanation: | ||
| + | |||
| + | "$" = Start | ||
| + | "XX" = Source device (https://de.wikipedia.org/wiki/NMEA_0183#Ger%C3%A4te-IDs) | ||
| + | BD = Beidu | ||
| + | GA = Galileo | ||
| + | GL = GLONASS | ||
| + | GP = GPS | ||
| + | GN = GNSS position fix from more than one constellation (eg. GPS + GLONASS) | ||
| + | "YYY" = Record | ||
| + | RMC = Recommended Minimum Sentence C (used in most cases) | ||
| + | GGA = Global Positioning System Fix Data | ||
| + | GNS = GNSS fixed data | ||
| + | GLL = Geographic Position - Latitude/Longitude | ||
| + | ... | ||
| + | |||
| + | Source: https://de.wikipedia.org/wiki/NMEA_0183 | ||
| + | </code> | ||
| + | |||
| ====== SDK Script gps-udp-client-GNSStoGPS.are ====== | ====== SDK Script gps-udp-client-GNSStoGPS.are ====== | ||
| + | <code c gps-udp-client-gnsstogps.are> | ||
| /* DESC: This script sends the local GPS NMEA stream to a remote UDP server. | /* DESC: This script sends the local GPS NMEA stream to a remote UDP server. | ||
| * DESC: It checks for the correct CR/LF end of line characters and convert messages $GN to $GP | * DESC: It checks for the correct CR/LF end of line characters and convert messages $GN to $GP | ||
| Line 22: | Line 52: | ||
| nb_config_set("gpsd.0.status=0"); | nb_config_set("gpsd.0.status=0"); | ||
| - | sleep(3); | + | do { |
| + | sleep(3); | ||
| + | } while ( nb_config_done != 0) | ||
| + | |||
| nb_config_set("gpsd.0.status=1"); | nb_config_set("gpsd.0.status=1"); | ||
| - | sleep(5); | + | do { |
| + | sleep(5); | ||
| + | } while ( nb_config_done != 0) | ||
| return 0; | return 0; | ||
| } | } | ||
| - | |||
| int gpsd_connect () | int gpsd_connect () | ||
| { | { | ||
| Line 38: | Line 71: | ||
| exit(-1); | exit(-1); | ||
| } | } | ||
| - | for (attempt = 0; attempt <= 5; attempt++) { | + | for (attempt = 0; attempt <= 15; attempt++) { |
| - | sleep(3); | + | sleep(15); |
| if (connect(gpsd, local_ip, local_port) < 0) { | if (connect(gpsd, local_ip, local_port) < 0) { | ||
| nb_syslog("Could not connect to daemon"); | nb_syslog("Could not connect to daemon"); | ||
| - | if (attempt == 3) { | + | if (attempt == 12) { |
| nb_syslog("Unable to connect, restarting daemon"); | nb_syslog("Unable to connect, restarting daemon"); | ||
| gpsd_restart(); | gpsd_restart(); | ||
| Line 52: | Line 85: | ||
| } | } | ||
| nb_syslog("Connected to daemon, requesting NMEA"); | nb_syslog("Connected to daemon, requesting NMEA"); | ||
| - | send(gpsd,"R=1\n"); | + | send(gpsd, "R=1\n"); |
| nb_syslog("Processing NMEA"); | nb_syslog("Processing NMEA"); | ||
| return gpsd; | return gpsd; | ||
| + | } | ||
| + | |||
| + | string checksum(string s) | ||
| + | { | ||
| + | pos = strchr(s, "*"); | ||
| + | |||
| + | if (is_void(pos)) | ||
| + | return s; /* no checksum to correct */ | ||
| + | |||
| + | cs = 0; | ||
| + | chars = explode(s); | ||
| + | for (i = 1; i < pos; i++) { /* skip $ and *XX */ | ||
| + | c = ord(chars[i]); | ||
| + | cs ^= c; | ||
| + | } | ||
| + | r = sprintf("%s%02X%s", substr(s, 0, pos + 1), cs, substr(s, pos + 3)); | ||
| + | return r; | ||
| } | } | ||
| Line 70: | Line 120: | ||
| /* open UDP server socket */ | /* open UDP server socket */ | ||
| server = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); | server = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); | ||
| - | if(server < 0) { | + | if (server < 0) { |
| nb_syslog("Unable to open socket"); | nb_syslog("Unable to open socket"); | ||
| exit(-1); | exit(-1); | ||
| Line 104: | Line 154: | ||
| data = recv(gpsd); | data = recv(gpsd); | ||
| len = strlen(data); | len = strlen(data); | ||
| - | printf("received %d\n", len); | ||
| /* Check for correct framing: CR+LF */ | /* Check for correct framing: CR+LF */ | ||
| if(len > 2) { | if(len > 2) { | ||
| Line 123: | Line 172: | ||
| } | } | ||
| /* Convert message $GN to $GP for backward compatibility */ | /* Convert message $GN to $GP for backward compatibility */ | ||
| - | printf("vor %s\n", data); | ||
| if(strstr(data, "$GN") == 0) {; | if(strstr(data, "$GN") == 0) {; | ||
| a_arr = explode(data); | a_arr = explode(data); | ||
| a_arr[2] = "P"; | a_arr[2] = "P"; | ||
| - | data = implode(a_arr); | + | data = checksum(implode(a_arr)); |
| } | } | ||
| - | printf("nach %s\n", data); | ||
| /* skip all messages different from GPGGA | /* skip all messages different from GPGGA | ||
| * if(strstr(data,"$GPGGA")==()) | * if(strstr(data,"$GPGGA")==()) | ||