Restricting BCM4354 to 802.11b only

Adrian Chadd

2017-10-06 21:53:18 UTC

I'm developing on an nVidia TX1 SOM which has an integrated BCM4354 chipset.
The SOM is running Ubuntu 16.04 Linux (64-bit ARM)
I have an application where I need long range with low bandwidth
requirements. It seems that 802.11b has the best receive sensitivity, and I
need to reduce latency caused by modulation switching (i.e. 802.11 b, g, n
etc). I'm looking for a way to configure the BCM43 chipset to lock in to
802.11b mode only, so I want to disable 802.11g and 802.11n modes.
I'm capable of making kernel driver modifications if necessary, but I don't
have the required information to do this. I've seen references on google to
the Broadcom WLAN client utility, or "wl", but it's not freely available
anywhere.
Does anyone have any advice on where to turn for information on how to do
this? Thanks.

Hi,

Have you noticed any actual modulation switching latency? Ideally it's
just enabling a different PHY path and so the latency should be
effectively nil.

Also, BCM4354 is a fullmac SDIO 11ac chip, not a b43 chip. :-)

And the TL;DR is - yes, there'll be an ioctl command to send to the
chip to tell it which PHY mode to operate in, and I bet you can set it
to operate on 'b' only. I just don't know off-hand on the brcmfmac
driver what that is, and you should likely ask on linux-wireless where
the brcmfmac people watch out.

-adrian