How to route GPS PPS from RAK5146 to Raspberry Pi GPIO using RAK2287/RAK5146 Pi HAT

LPWAN Industrial Gateways / Concentrators
1

Hello RAK Team,

I am using the following hardware:

  • RAK5146 SPI LoRa Concentrator with built-in ZOE-M8Q GPS
  • RAK2287 / RAK5146 Raspberry Pi HAT
  • Raspberry Pi CM4 with CM4 IO Board
  • ChirpStack Gateway OS (OpenWrt, kernel 6.6.104)

From the RAK5146 datasheet and schematic, I understand that:

  • The GPS PPS signal (from ZOE-M8Q TIMEPULSE) is available on the RAK5146 golden finger pin 19 (PPS)
  • PPS is internally connected to the SX1302/SX1303 for fine timestamping
  • However, on the RAK2287 / RAK5146 Pi HAT, PPS is not routed to any Raspberry Pi 40-pin GPIO (GPIO4, GPIO26, etc. are marked NC)

My goal is to use Linux PPS (/dev/pps0) on the host Raspberry Pi, not only the internal SX1302 timestamping.

I would like to ask:

  1. Is there an official or recommended method to route the GPS PPS signal from RAK5146 to a Raspberry Pi GPIO when using the RAK5146 Pi HAT?
  2. Are there any test pads, vias, or alternate pins on the HAT that expose the PPS signal?
  3. Does RAK recommend a hardware modification (jumper / wire) from golden finger pin 19 (PPS) to a specific Raspberry Pi GPIO (e.g. GPIO4)?
  4. Is there any future HAT revision or reference design that supports PPS-to-host GPIO directly?

Currently, Linux PPS works only after manually wiring PPS to a Pi GPIO, but I would like to confirm the correct and supported approach from RAK.

Thank you for your support.

Best regards,
Satyendra