OK, some progress.
First of all there was a dry joint on my TX wiring Fixing that means I get reliable data from the module.
In case I’d screwed something up at system level, I did a clean install of Stretch and got the GPS module set up and working first. That gets me reliable position information on ttyAMA0. Yay.
$GPRMC,225036.000,A,51xx.xxxx,N,000xx.xx,W,0.00,200.38,090318,A*71
I then installed and configured the LoRa software per the ttn-zh wiki (https://github.com/ttn-zh/ic880a-gateway/wiki). Everything is up and running and the concentrator appears to be seeing the GPS:
Mar 9 22:47:09 ttn-dev-gw ttn-gateway[538]: INFO: Reference longitude is configured to 0.000000 deg
Mar 9 22:47:09 ttn-dev-gw ttn-gateway[538]: INFO: Reference altitude is configured to 0 meters
Mar 9 22:47:09 ttn-dev-gw ttn-gateway[538]: INFO: GPS is enabled
I say ‘appears’… it isn’t throwing any errors about opening the serial port. I’m slightly suspicious that I can still cat /ttyAMA0 in another shell. However:
Mar 9 22:49:32 ttn-dev-gw ttn-gateway[538]: ### [GPS] ###
Mar 9 22:49:32 ttn-dev-gw ttn-gateway[538]: # Invalid gps time reference (age: 1520635659 sec)
Mar 9 22:49:32 ttn-dev-gw ttn-gateway[538]: # Manual GPS coordinates: latitude 0.00000, longitude 0.00000, altitude 0 m
Mar 9 22:49:32 ttn-dev-gw ttn-gateway[538]: ##### END #####
I’m getting this despite the fact that the timestamp on each sentence format is correct. I’ve also patched the PPS output from the GPS module to pin 19 on the iC880a concentrator.
I’m prepared to look at the resin option, but it feels like I’m so close that I’d really like to get it working as it stands…!
Mark
PS: fun fact - another problem I found was that with the module and antenna in the case, it doesn’t get a fix; with them out of the case, it works. The module (not antenna) was sandwiched between Raspi and concentrator - is it possible RFI was interfering with the signal? It’s still indoors by the way.