"Writing multiple SOH"
Most likely not the problem what AP has but I think its good to mention also in this thread: https://forum.mysensors.org/post/56960

V_HVAC_FLOW_MODE, V_HVAC_SPEED and V_HVAC_FLOW_STATE handling still missing.
No smartSleep implementation yet.

I think there is couple things you need to tweak if you want to use SoftwareSerial instead of AltSoftSerial since its quite well baked in the default solution.

See these:

• https://github.com/mysensors/MySensors/blob/development/MySensors.h#L298
• https://github.com/mysensors/MySensors/blob/development/core/MyTransportRS485.cpp#L99

Will the result change if you add more sync(SOH) chars?

@kimot what hw you are using? MCP2515 + MCP2551?

@Reza have you tried to use terminating resistors?

And perhaps it could be good to try 1k pull-up and pull-downs at the gateway end. The left diagram:

With these two tricks I got my setup stable.

And a little tweak to transport class could help also..

@Anticimex
Have you measured or know someone who has or can you estimate how much the communication takes time with one "relay on" command for example?
1ms, 10ms or 100ms?

@frazzle said:

Now my questions:

• Can send and receive messages without a controller? How would I go about that?
• How secure is the NRF24 connection? To be clear, I don't mind anybody reading what's being sent, but I don't want someone sending commands to my stations and thus triggering the relays (it's very unlikely, but you never know )
• Is there a way to report signal strength between the gateway and the wireless station?
• Any other tips you can give me?

Thanks for reading

1. Yes you can. Take a look at serial api documentation. You need to implement "controller" software by yourself.
2. Use signing. You can find more information from here
3. Not really. nRF24 library support only check if signal => -64dBm or not.. see this
4. It might be easier to use arduino as gw. See ACK functionality from documentation for resending the lost packages.

Currently there is no "hw" ack functionlity like the radio has.
You can check out the rs485 transmit code from here.

But you can of course use the ack functionality between controller software and node to make sure message will get to destination.