RAK7258 and GPS receiver connectivity

Issue:
Mon Nov 2 19:45:36 2020 user.info lora_pkt_fwd[1601]:
INFO: Disabling GPS mode for concentrator’s counter…
Mon Nov 2 19:45:36 2020 user.info lora_pkt_fwd[1601]: INFO: host/sx1301 time offset=(1604362993s:600141µs) - drift=164µs
Mon Nov 2 19:45:36 2020 user.info lora_pkt_fwd[1601]: INFO: Enabling GPS mode for concentrator’s counter.
. . .
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd[1601]: ### [GPS] ###
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd[1601]: # Invalid time reference (age: 1604364337 sec)
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd[1601]: # no valid GPS coordinates available yet
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd[1601]: ##### END #####

Setup:
Everything is the same as in the original package, the LTE module works with an AT&T SIM card.
GPS receivers were tested from the RAK5205 tracker, from the SIM7600 LTE module development kit and the embedded no-name.

LoRa® Server:
Used packet forwarder for TTN

Details:
I received a new RAK7258 (LTE), and made sure that the connector for the GPS receiver is soldered inside it (this is quite reasonable, given that the LTE module EG95-NA is used).
Actually, I am interested in two questions:

  1. How to use the GPS-receiver?
  2. How to get coordinates (so that the gateway can display them on the “LoRa Gateway” -> “LoRa Packet Forwarder” page, “GPS Information” tab).
    The LTE module works, but the system log constantly displays:

Mon Nov 2 19:45:36 2020 user.info lora_pkt_fwd [1601]:
INFO: Disabling GPS mode for concentrator’s counter …
Mon Nov 2 19:45:36 2020 user.info lora_pkt_fwd [1601]: INFO: host / sx1301 time offset = (1604362993s: 600141µs) - drift = 164µs
Mon Nov 2 19:45:36 2020 user.info lora_pkt_fwd [1601]: INFO: Enabling GPS mode for concentrator’s counter.

Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]:

2020-11-03 00:45:37 UTC

Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: ### [UPSTREAM] ###
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # RF packets received by concentrator: 2
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # CRC_OK: 100.00, CRC_FAIL: 0.00, NO_CRC: 0.00
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # RF packets forwarded: 2 (78 bytes)
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # PUSH_DATA datagrams sent: 3 (587 bytes)
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # PUSH_DATA acknowledged: 100.00
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: ### [DOWNSTREAM] ###
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # PULL_DATA sent: 6 (100.00 acknowledged)
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # PULL_RESP (onse) datagrams received: 1 (182 bytes)
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # RF packets sent to concentrator: 1 (12 bytes)
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # SX1301 time (PPS): 1343305069, offset us 0
Mon Nov 2 19:45:37 2020 user.info lora_pkt_fwd [1601]: src / jitqueue.c: 456: jit_print_queue (): INFO: [jit] queue is empty
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: ### [GPS] ###
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # Invalid time reference (age: 1604364337 sec)
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: # no valid GPS coordinates available yet
Mon Nov 2 19:45:37 2020 user.notice lora_pkt_fwd [1601]: ##### END #####

That is, as I understand it, the gateway receives a timestamp, but, for some reason, rejects the coordinates as invalid.

How to solve this problem?

Hi @Mic29,
As I understood you are waiting for GPS coordinates from the gateway. Am I right? You can’t get this data because RAK7258 does not support GPS.

Well, but the RAK7285 (LTE version) supports the EG95 LTE module, which in turn supports GPS and GPS-A. Moreover, the connector for connecting the GPS receiver to this module is soldered to the main board of the gateway.
Thus, all the work on obtaining coordinates and exact time falls on the LTE module, and the gateway only needs to request (receive) this data from the module.
Judging by the contents of the log, RAK7285 “understands” that there is a connected GPS receiver, is trying to get a time stamp and possibly coordinates.
Perhaps I am misunderstanding something, but it seems to me that for the gateway it is necessary either to specify a certain serial device from where it can take this data, or to indicate where the data stream from this serial device should be redirected.
Unfortunately, I am not very good at OpenWRT and its capabilities.

Hi Nikola!
I understand correctly that the same thing happens to me as described in the post Add GPS to RAK7258?
That is, the original firmware does not process the received data?

That is, in theory, I need to redirect the data stream from the GPS receiver to the /dev/ttyS1 device.
The problem is that this data will not be received and processed by the RAK7258 firmware, right?