Thread: [Madwifi-devel] EEPROM content differences in two SMC2335W - calibration data?
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From: Joerg A. <ja...@gm...> - 2007-08-26 18:15:18
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Hi, I've got two SMC2335W EU CardBus cards (FCCID JI5SMC2335WR) and while trying to find out their differences to a Netgear WAG511 (H/W: 0.1, FCCID PY3WAB501) I'm rather suprised by finding differences in the EEPROM contents of the two SMC2335W. Beside the different MAC addresses, they differ at the offsets 0x180, 0x1df, and 0x200-0x280 (EEPROM version 3.2) Does anyone knows what these differences are? The header files of OpenHal don't give a hint. Is each Atheros card individually calibrated during production? BTW, the FCC docs of SMC2335W and WAG511 both refer to the same Atheros reference design, but the first one is 802.11ab while the latter one is 802.11abg. Any chance to "add" 802.11g to the SMC2335W? /Joerg |
From: Alfred A. <al...@cc...> - 2007-08-26 18:48:07
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Hello Joerg, nice to hear you're still around ;-) >I've got two SMC2335W EU CardBus cards (FCCID JI5SMC2335WR) and >while trying to find out their differences to a Netgear WAG511 >(H/W: 0.1, FCCID PY3WAB501) I'm rather suprised by finding >differences in the EEPROM contents of the two SMC2335W. >Beside the different MAC addresses, they differ at the offsets >0x180, 0x1df, and 0x200-0x280 (EEPROM version 3.2) > >Does anyone knows what these differences are? The header files of >OpenHal don't give a hint. >Is each Atheros card individually calibrated during production? Correct. The transmit section of Atheros-based WLAN cards contains programmable amplifiers and these amplifiers are calibrated during production. Roughly said, the EEPROM contains tables that say 'if you set the amplifier to x at a frequency of y MHz, then the output power will be z dBm'. Software in the HAL performs the necessary interpolations to get the desired output power at the given frequency. >BTW, the FCC docs of SMC2335W and WAG511 both refer to the same Atheros >reference design, but the first one is 802.11ab while the latter one is >802.11abg. Any chance to "add" 802.11g to the SMC2335W? Not really. The AR5211 MAC/BB in the 802.11ab design is not capable to do CCK and OFDM modulation simultaneously. One could construct a 'g-only' mode with OFDM modulation at 2.4 GHz, but it is of limited value in practice - an 11g radio is expected to be able to receive data with CCK rates. Best regards Alfred Arnold -- Alfred Arnold E-Mail: al...@cc... Computer Club at the http://john.ccac.rwth-aachen.de:8000/alf/ Technical University Phone: +49-241-406526 of Aachen Fax: +49-241-406527 |
From: Joerg A. <ja...@gm...> - 2007-08-26 21:42:05
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Alfred Arnold writes: > nice to hear you're still around yes, recently moved to a DSL-free area in Berlin and now I'm a bit involved with Freifunk mesh networking. > Correct. The transmit section of Atheros-based WLAN cards contains > programmable amplifiers and these amplifiers are calibrated during > production. Roughly said, the EEPROM contains tables that say 'if you set > the amplifier to x at a frequency of y MHz, then the output power will be > z dBm'. Software in the HAL performs the necessary interpolations to get > the desired output power at the given frequency. Thanks for the quick explanation. Copying the WAG511 eeprom onto the SMC2335W would put the wrong calibration values there (and be of limited help with 802.11g, see below). > >BTW, the FCC docs of SMC2335W and WAG511 both refer to the same Atheros > >reference design, but the first one is 802.11ab while the latter one is > >802.11abg. Any chance to "add" 802.11g to the SMC2335W? > > Not really. The AR5211 MAC/BB in the 802.11ab design is not capable to do > CCK and OFDM modulation simultaneously. One could construct a 'g-only' > mode with OFDM modulation at 2.4 GHz, but it is of limited value in > practice - an 11g radio is expected to be able to receive data with CCK > rates. Both FCC applications of SMC2335W and WAG511 claim to be electrical identical to the Atheros PPD-AR5BCB-00022. The WAG511 was sold as a 802.11abg card. I've looked into the user manual of the Atheros card and it really mentions a "pure g" mode only. CCK is needed for "mixed mode", i.e. RTS/CTS protection of g traffic against b neighbours, isn't it? So the WAG511 hasn't got a complete 802.11g implementation :-( Regards, Jörg. |