Hello Benoit,
Regarding the Half/Quarter channel support in madwifi-free; does it
also implement possible changes in the center frequency ?
Is that possible to select different center frequencies? e.g. for
quarter channels in 802.11a use channels 37, 38 and 39, ...
If not, what should be required to do that?
Regards
Marcel
On 06/29/2010 12:10 PM, Steve Brown wrote:
> On 06/28/2010 12:17 AM, Benoit Papillault wrote:
>
>> Le 25/06/2010 22:08, Steve Brown a écrit :
>>
>>> I see that there are some TO DO comments in the ath5k code for
>>> half/quarter channels. Is this being worked on?
>>>
>>> If not and somebody on the list has the needed info and would be willing
>>> to suffer some dumb questions, I'll try to add it.
>>>
>>> Steve
>>>
>> Hi Steve,
>>
>> Reading ath5k, I gathered the following information :
>>
>> /*
>> * PHY timing register 3 [5112+]
>> */
>> #define AR5K_PHY_TIMING_3 0x9814
>> #define AR5K_PHY_TIMING_3_DSC_MAN 0xfffe0000
>> #define AR5K_PHY_TIMING_3_DSC_MAN_S 17
>> #define AR5K_PHY_TIMING_3_DSC_EXP 0x0001e000
>> #define AR5K_PHY_TIMING_3_DSC_EXP_S 13
>>
>> This describe the mantissa (MAN) and exponent (EXP) of the clock used
>> to compute the center frequency. This value is divided by 2 for 10 MHz
>> channels.
>>
>> /*
>> * PHY PLL (Phase Locked Loop) control register
>> */
>> #define AR5K_PHY_PLL 0x987c
>> #define AR5K_PHY_PLL_HALF_RATE 0x00000100
>> #define AR5K_PHY_PLL_QUARTER_RATE 0x00000200
>>
>> For 802.11a (40MHz PLL), bit AR5K_PHY_PLL_HALF is set to get 10 MHz
>> channels. That's probably the most important register.
>>
>> /*
>> * PHY mode register [5111+]
>> */
>> #define AR5K_PHY_MODE 0x0a200 /*
>> Register Address */
>> #define AR5K_PHY_MODE_MOD 0x00000001 /* PHY
>> Modulation bit */
>> #define AR5K_PHY_MODE_MOD_OFDM 0
>> #define AR5K_PHY_MODE_MOD_CCK 1
>> #define AR5K_PHY_MODE_FREQ 0x00000002 /* Freq mode
>> bit */
>> #define AR5K_PHY_MODE_FREQ_5GHZ 0
>> #define AR5K_PHY_MODE_FREQ_2GHZ 2
>> #define AR5K_PHY_MODE_MOD_DYN 0x00000004 /* Enable
>> Dynamic OFDM/CCK mode [5112+] */
>> #define AR5K_PHY_MODE_RAD 0x00000008 /* [5212+] */
>> #define AR5K_PHY_MODE_RAD_RF5111 0
>> #define AR5K_PHY_MODE_RAD_RF5112 8
>> #define AR5K_PHY_MODE_XR 0x00000010 /* Enable XR
>> mode [5112+] */
>> #define AR5K_PHY_MODE_HALF_RATE 0x00000020 /* Enable Half
>> rate (test) */
>> #define AR5K_PHY_MODE_QUARTER_RATE 0x00000040 /* Enable
>> Quarter rat (test) */
>>
>> For 10 MHz channels, AR5K_PHY_MODE_HALF_RATE needs to be set.
>>
>> There are also some information on madwifi-free :
>> http://madwifi-project.org/browser/madwifi/trunk/ath_hal/ar5212/ar5212_reset.c
>>
>>
>> I've not played myself with those bits, but that could be a good
>> starting point for you.
>>
>> Regards,
>> Benoit
>>
> Benoit, thanks for your comments.
>
> In looking more closely at madwifi-free, I now see that half/quarter
> channel is implemented. In fact, setting the country code to 5001
> selects the channel mappings for my XR9 card and includes half/quarter
> channels. I verified the channel widths with a spec analyzer. 5MHz and
> 10MHz widths are properly selected. Scanning is slightly broken, but it
> looks very close.
>
> I'm sure that everything I need is there.
>
> Steve
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>
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