time field empty when no GPS present

[jpmeijers]

Looking at the PROTOCOL

packet_forwarder/PROTOCOL.TXT

Lines 133 to 135 in d0226ea

	time | string | UTC time of pkt RX, us precision, ISO 8601 'compact' format
	tmms | number | GPS time of pkt RX, number of milliseconds since 06.Jan.1980
	tmst | number | Internal timestamp of "RX finished" event (32b unsigned)

And then at the code

packet_forwarder/lora_pkt_fwd/src/lora_pkt_fwd.c

Lines 1609 to 1637 in d0226ea

	/* Packet RX time (GPS based), 37 useful chars */
	if (ref_ok == true) {
	/* convert packet timestamp to UTC absolute time */
	j = lgw_cnt2utc(local_ref, p->count_us, &pkt_utc_time);
	if (j == LGW_GPS_SUCCESS) {
	/* split the UNIX timestamp to its calendar components */
	x = gmtime(&(pkt_utc_time.tv_sec));
	j = snprintf((char *)(buff_up + buff_index), TX_BUFF_SIZE-buff_index, ",\"time\":\"%04i-%02i-%02iT%02i:%02i:%02i.%06liZ\"", (x->tm_year)+1900, (x->tm_mon)+1, x->tm_mday, x->tm_hour, x->tm_min, x->tm_sec, (pkt_utc_time.tv_nsec)/1000); /* ISO 8601 format */
	if (j > 0) {
	buff_index += j;
	} else {
	MSG("ERROR: [up] snprintf failed line %u\n", (__LINE__ - 4));
	exit(EXIT_FAILURE);
	}
	}
	/* convert packet timestamp to GPS absolute time */
	j = lgw_cnt2gps(local_ref, p->count_us, &pkt_gps_time);
	if (j == LGW_GPS_SUCCESS) {
	pkt_gps_time_ms = pkt_gps_time.tv_sec * 1E3 + pkt_gps_time.tv_nsec / 1E6;
	j = snprintf((char *)(buff_up + buff_index), TX_BUFF_SIZE-buff_index, ",\"tmms\":%llu",
	pkt_gps_time_ms); /* GPS time in milliseconds since 06.Jan.1980 */
	if (j > 0) {
	buff_index += j;
	} else {
	MSG("ERROR: [up] snprintf failed line %u\n", (__LINE__ - 4));
	exit(EXIT_FAILURE);
	}
	}
	}

time should contain an ISO time, irrelevant if the gateway is GPS synced or not. Maybe it's NTP synced, and the should be good enough to indicate at what time a packet was received.

tmms should contain the GPS timestamp in case a GPS is present.

tmst contains the concentrator clock counter value used to schedule downlinks accurately.

My opinion is that this line

packet_forwarder/lora_pkt_fwd/src/lora_pkt_fwd.c

Line 1613 in d0226ea

if (j == LGW_GPS_SUCCESS) {

should be removed.

[jpmeijers]

I was expecting to see the time field being added when fake_gps is enabled, but that does not seem to work.

Fake GPS off (metadata from TTN):

{
   "gtw_id":"eui-60c5a8fffeXXXXXX",
   "timestamp":11257844,
   "time":"",
   "channel":5,
   "rssi":-38,
   "snr":9.5,
   "rf_chain":0
}

Fake GPS on:

{
   "gtw_id":"eui-60c5a8fffeXXXXXX",
   "timestamp":600364156,
   "time":"",
   "channel":5,
   "rssi":-38,
   "snr":9,
   "rf_chain":0,
   "latitude":"<REDACTED>",
   "longitude":"<REDACTED>",
   "altitude":190
}

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