max number of end-device supported in tunnel mode of openthread when nRF52840 works as router

[Pandurang]

Hello All,

We are in the evaluation phase to implement openthread network in our gateway using nRF52840 as NCP device.

We require to have the number of end-device supported by nRF52840 working as NCP device

Open Thread network says, maximum 32 routers can be connected and 511 end-devices per router.

At this link, we found that with available memory in nRF52840, maximum 160 end-devices can be connected at a time. Actually, 160 is the value of maximum message buffers.

As we know, openthread has two modes - Full Stack and Tunnel mode.

In above link, it is not mentioned which mode is used. So, I assume, it would be Full Stack mode. Is this correct?

So, my query is how many maximum number of end-devices supported by nRF52840 in tunnel mode of OpenThread?

Any hint or guide will be very helpful.

Thanks.

[Jørgen Holmefjord]

Hi,

At this link, we found that with available memory in nRF52840, maximum 160 end-devices can be connected at a time. Actually, 160 is the value of maximum message buffers.

160 message buffers is not the maximum, this is the default configured number of buffers. The nRF52840 have 256 kB RAM available, so it is likely that you can increase this number quite a bit before running out of RAM. The total RAM usage in all measured example application with the default configs, are less than half of the available RAM space, see Flash and RAM requirements for nRF52840.

As we know, openthread has two modes - Full Stack and Tunnel mode.

I have actually never heard of these terms in connection with OpenThread before, but I see that they are mentioned in the old Thread and Zigbee SDK v1.0.0 documentation. I believe that these terms now have been replaced by the terms NCP and RCP.

In above link, it is not mentioned which mode is used. So, I assume, it would be Full Stack mode. Is this correct?

My answers in the linked thread was assuming System-on-Chip designs, which means that the Full OpenThread stack runs on the SoC.

So, my query is how many maximum number of end-devices supported by nRF52840 in tunnel mode of OpenThread?

Since the OpenThread stack will run on the host processor in RCP mode, the buffers will be stored in the RAM of the host processor. How many buffers the host processor can store depends on which host processor are used, and the size of its available RAM.

Best regards,
Jørgen