RAK3172 Node Join Issue with RAK7268CV2 Gateway (EU868) – RX_TIMEOUT

LPWAN Modules / EVBs RAK3172
1

Hi all,

I’m facing an issue with a RAK3172 node joining a RAK7268CV2 (External Antenna) gateway using EU868 frequency. Here’s the situation:

Working setup:

  • Node: RAK3172
  • Gateway: RAK5146
  • Frequency: EU868
  • Network Server: ChirpStack
  • Node is able to join and communicate successfully.
    Problematic setup:
  • Node: Same RAK3172
  • Gateway: RAK7268CV2 (External Antenna)
  • Frequency: EU868
  • Node fails to join – I’m seeing EVT:JOIN_FAILED_RX_TIMEOUT.

What I’ve checked/tried so far:

  1. Confirmed OTAA keys and DevEUI are correct.
  2. Tried different antennas (3 types).
  3. Verified frequency (EU868 and also tried IN865).
  4. Node is not receiving any packets from the gateway during RX window.
  5. Other nodes are working fine with the same RAK7268CV2 gateway.
  6. The same node works fine with RAK5146.

Observations:

  • The issue seems to be that this particular RAK3172 node cannot receive downlink packets from RAK7268CV2, causing join failures.

My question:

  • What could cause this node to fail with RAK7268CV2 while working fine with RAK5146?
  • Any suggestions on settings to check on the gateway or node to fix the RX_TIMEOUT issue?
  • Could it be related to gateway configuration, antenna mismatch, or timing issues specific to this node?

Any help would be greatly appreciated!

2

Welcome to RAK forum @DiVyEsH ,

You already did good troubleshooting.

Some ideas I have:

  1. You saw the issue when you shift to a different gateway with external antenna. If you are using ChirpStack, do you see the join uplink attempts? Are there any error shown? If there is error related to collision, the node and the gateway might be too close to each other. Put it in the next room or try to test some meters away.
  2. You can try to full chip erase the RAK3172 then reupload a fresh RUI3 firmware, this way we can remove any firmware related issue.
3

Thank you, @carlrowan.
The problem was resolved after I replaced the RAK3172 chip. The join uplink is now being received by the gateway, and data is successfully reaching ChirpStack.

However, I still don’t know what was wrong with the old RAK chip. The AT commands were working fine also i did full chip erase several times and reuploaded fresh RUI3 Firmware, but the chip wasn’t sending any uplinks to the gateway.

4

Good news you have a working setup now.

With the problematic RAK3172, some ideas.

  1. Maybe it got damaged, electrically (like ESD) or mechanically (if subjected to extreme drop/vibration).
  2. You can try to do LoRa P2P on to see if the issue is really on the RF frontend part of the module.
  3. You can try to do continuous wave (AT+CW=868000000:14:5) and see on SDR (if you have) for RF signals.