CAD function

1

Hi,
Can anyone please explain the difference between Radio.StartCad and Radio.SetRxDutyCycle?

I am clear with the SetRxDutyCycle function but not sure what is the difference between CAD and duty cycle? Don’t they both just detect preamble only?

2

Can you provide a little more context - device, software, hardware etc

3

I am using semtech SX1262 for LoRa (STM32WL) and using STM32CubeIDE.
I am a bit confused about CAD, should I use CAD or Duty Cycle on receiver end to listen to preamble sent by Transmitter?
https://semtech.my.salesforce.com/sfc/p/#E0000000JelG/a/2R000000HT76/7Nka9W5WgugoZe.xwIHJy6ebj1hW8UJ.USO_Pt2CLLo

4

Are you using LoRa to LoRa?

It is a significant task to write a LoRaWAN stack - which is what we cover here in relation to the TTN. A general LoRa question is off topic here I’m afraid.

5

Ok, thanks.

6

CAD does not detect preamble only, it detects LoRa modulation in general, i.e. even a payload will be detect by a CAD (which stands for Channel Activity Detection). It is particularly useful in listen-before-talk.

1 Like
7

Thanks.
So is it the right approach to think that CAD is a replacement for RxDutyCycle?

8

No the goal of each function are very different:

  • with RxDutyCyle, you check regularly if a packet arrives: if you get a preamble you continue the reception of the packet, otherwise you go to sleep, and will retry at a later time.
  • with CAD you just check is there any activity at the moment on the channel with a particular SF. You typically use this not to receive an incoming packet, but so that you can send a packet without collision with a packet currently being transmitted. Check the chapter 6.1.5 it explain this maybe better than me.
9

Sorry gents, but this is not the forum you are looking for.

Unless it is explicitly LoRaWAN on TTN, it’s not on topic.