On 16 July 2014 10:38, Simon Wunderlich <sw@xxxxxxxxxxxxxxxxxx> wrote: > >> On Wednesday 16 July 2014 08:24:58 Michal Kazior wrote: >> > > * So far, we always get 64 bins of fft data in the samples, even if we >> > > >> > > are in HT40 or VHT80 mode. That doesn't seem right, as there should >> > > be more bins for wider channels (e.g. 128 or 256 bins). Is there any >> > > parameter to change in the configuration to get the output from >> > > multiple channels / higher bandwidth? >> > >> > Hmm.. I suspect this may be because you use scan command. Scanning >> > uses channel list which is programmed with legacy modes a and g >> > (implying 20Mhz). Perhaps that's the limiting factor now. Using other >> > (wider) modes breaks scan from what I remember but it might be worth >> > checking out if it impacts fft bin sizes. >> >> I did the HT80 and HT40 stuff on a single channel in the spectral >> "background" mode. They reports from the firmware (10.1) still only had 64 >> bins. The HT80 stuff wasn't tested with the "main" firmware because it >> refused to switch to HT80 mode as AP/Sta. > > Just to clarify this a little more, we tried AP (running hostapd) as well a > STA in 40 and 80 MHz modes. We always got 64 bins returned. It seems the number of bins is 2^ (fft_size - bin_scale) = 2^(7-1) = 64. Changing fft_size to 9 yields 256 bins. Perhaps fft reports are (implicitly) relative to the mode the hw is in at a given time and if you want a reasonable bin resolution for, e.g. VHT80 you need to increase fft_size? Michał -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
