Re: antenna diversity / antsel configuration

From: Jouni Malinen (
Date: 2002-07-23 21:14:53 UTC

On Tue, Jul 23, 2002 at 01:23:53PM -0700, Michael Codanti wrote:

> Have you tested a Prism 2.5 PCMCIA card with Primary 1.1.0, Station 1.4.2
> yet? I got one here but I don't have a Linux box with me to test it in.

Yes and it did not work (or to be more exact, Host AP mode's probe request responding did not work). I would like to know whether this works with station firmware 1.4.1 or 1.4.x with x>2..

> Now for my request.. We are getting a bunch of cards wth only external
> antenna connectors, and we want to only use one antenna on it. From what I
> have been told the HostAP driver does not currently support telling the card
> to use just one of the antenna ports. (i.e. turning diversity off) How
> difficult would that be to do?

There is no explicit option for this in the driver, but this should be doable using BBP configuration with writemif. I haven't tested this, so if you do, please let me know if it works..

Check Intersil's BBP data sheet for more details. Briefly, antenna configuration seems to be configured with CR9 (TX) and CR10 (RX).

'iwpriv wlan0 readmif 18' reads CR9 (gives 162 on a Prism2.5 PCI) and correspondingly readmif 20 reads CR10 (200).

CR9 bit1: 0=set AntSel pin to value in bit2

          1=set AntSel pin to antenna for which last valid headed CRC

CR9 bit2: 0=AntSel low, 1=AntSel high

CR10 bit0: 0=dual antenna for diversity, 1=single antenna CR10 bit1: 0=AntSel pin low, 1=AntSel high

I would interpret that so that no diversity and AntSel low could be set with:

iwpriv wlan0 writemif 18 160
iwpriv wlan0 writemif 20 201

and no diversity, AntSel high with:

iwpriv wlan0 writemif 18 164
iwpriv wlan0 writemif 20 203

Anyway, there might be differences between cards, so always better to read the original values and do bitops on them and write new values. You should also note that these values do not survive HW reset since they are not saved anywhere in the driver data.

If this works as expected, I could add option for configuring antsel for RX and TX with something like 0=diversity, 1=low, 2=high.

Jouni Malinen                                            PGP id EFC895FA

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