User:Robinc
From Rt2x00Wiki
This page is for my testing and development notes regarding rt2x00
Random notes, testing and thoughts are here, i may not follow instructions when testing as i want to see what works and what dosn't as the average user dosn't follow instructions either. Also these tests can verify regressions and new bugs
Contents |
My test setup
Toshiba Satelliite 2060CDS laptop 366Mhz 160M ram Debian unstable
Some notes on RSSI
After speaking to ivo I am doing some work on rssi and sensitivity calulations by looking at legacy code and doing some experiments.
With rt2500 Maximum collected RSSI seems to be 121 ( i have not quite observed 121 but got over 115 with touching antennas). I would assume if the antennas are physicaly connected 121 is what you would get. This seems to equate to 0dbm as the rssi to db offset is 121
dbm=rssi-121
Now averaging.
Ralink use a expodentaly decaying mean, this is very good at coping with environmental conditions changing unlike a normal mean and only uses a single storage location unlike a rolling mean. :-
Adv=Adv-(adv/8)+new_reading
the /8 can be efficienly done with a bit shift >>3
Becuause of the above code to get an actual value you must take adv and >>3 and the data passed to Asicbbptuning() is infact the real (not *8) value of adverage rssi.
So the first thing ralink do is convert rssi to dbm by taking off 121.
What i have noticed with rt2500 is that there is no tuning when not assicated, i think this is a bad idea because i started loosing beacons when the signal became very strong or very weak.
RT2500:-
BBP R17 is the Voltage Controlled Gain selector (VCG)
On The rt2500 when the chip initalises R17 is set to least default sensitivity which is 50, maximum sensitivity is set by code and is 64, but it appears that for very strong signals the lower level of gain has been reducde to 44 in rt2500
So this gives values for RT2500 BBP R17 (VCG) of Least sensitive 44 (decimal) Most sensitive 64 (decimal)
It is possible that more or less gain exists outside these ranges.
RT2400 :-
BBP Register for gain is R13
Seems max level is 0x20 for R13
Eeek can't find a minimum level presume its 0x00
Code does not look in as much detail as rt2500 does and levels
23-May-2007
Managed to get rt2500usb to kernel fault when unplugging the device, didn't record the backtrace however :-( and have not achieved same results.
Firmware location on debian unstable is /lib/firmware/
RT61pci hard faulted on an eject of card, partial backtrace points at rt61pci_txdone+0x26/0x58 [rt61pci], yep thats the EIP, stack context was :-
rt61pci_txdone+0x26/0x58 rt2x00pci_beacondone +0x2c/0x58 rt61pci_interrupt +0x9d/0xa6
22-May-2007
Testing rt2400 pci against office 802.11B AP and some nearby neighbours, network is 128bit wep encrypted
- Insert card, device detected and module installed, OK
- iwlist scanning, "wlan0 interface does not support scanning, network is down"
- ifconfig wlan0 up, "ADDRCONG(NETDEV_UP): wlan0 link is not ready"
- iwlist scanning, 2 cells detected, looks normal and correct
- Scanning results appear normal.
- Set WEP key, set ESSID, driver attempted association
- Makes whole buch of noise in logs but associates
- manual setting of ip address, ping sucessfull
- using dhclient requires some fighting and seems to cause loss of association. Have managed to get ip address. Think problem is caused by dhclient taking interface down and brining back up.
- repeat test, reinsert card, set essid, set key run dhclient, FAILED to do very much at all
- repeat test, reinsert card, bring up interface, set ESSID, set KEY, dhclient, SUCCESSFUL.
- repeat test, reinsert card, set ESSID, set KEY, bring interface up. No association attempted, set essid again, set key again, no association, 3rd time it worked.
- repeat test, setup debian /etc/network/interfaces file for wlan0. Ok this time it worked with a dhclient from the ifpreup stage you just need a little patience as the driver does not kick in to an association stright away.
- repeat above again, reinsert card, failed to enter associate attempt
Seems to not enter associate if not kicked in some way when the interface is up
Switch to RT2500USB
Similar problems with associating as rt2400. Can manualy associate by setting key and essid after interface up but logs so associated but cannot set ipaddress and sucessfully ping router