Missed packets in FSK packet mode

Hi all,

I’m writing a library that will support both LoRa and FSK modes. I wrote small test that will send several packets in FSK packet mode and receive it on the other end. However receiver gets only 2 out of 3 packets. When I put ~50ms delay between packets on the transmitter side, all packets successfully received by the receiver.

Transmitter works fine, here is spectrogram:

Screenshot 2023-05-01 at 11.21.08

On it there is a clear preamble, small packet, crc, preamble, bigger packet (63 bytes), crc, preamble and start of the biggest packet. Everything is transmitted one after another.

So I suspect something to do with RX synchroniser, that can’t get the lock.

I tried:

  • Call manual RX restart via RestartRxWithoutPllLock
  • Set up AutoRestartRxMode = 01, InterPacketRxDelay = 0 (default) to avoid additional delays in the chain.
  • Disable AfcAutoOn=0
  • Set RestartRxOnCollision=0

Nothing worked.

Is there any hidden latency on the receiver side? Is there a minimum delay between packets in FSK packet mode? Any other ideas?