Le 22/02/2014 11:43, Lars Bøgild Thomsen a écrit : > On Saturday 22 February 2014 10:11:08 Michel Stempin wrote: >>>> The main drawback of these modules is that they are not individually RF >>>> calibrated on the production line, resulting on poor/non conform WiFi >>>> performance. You can figure this out by reading the RF ART calibration >>>> partition on 2 random units: they will be the same, byte for byte :( >>> That is quite interesting information. I'll check my modules. >> Please let me know about the result, as I tested on mines and have it tested >> with another unrelated person from the forum and got the exact same ART >> partitions. THis may be different for your newer board, but you'd better >> check! > > For now I did a simple md5sum of the art partition on the two devices I have > and they are NOT identical! I have however no idea how to decode the > information contained in that partition, so whether that means they are not > calibrated I do not know. > > I am also not an RF engineer but I would suspect that the manufacturer could > get away with identical calibration on a device such as this. The > differences between the boards are probably not all that big. By the way - > don't they actually store the MAC address on that partition? If that is the > case they ought to be different.
Then you should be fine: the ones I tested carried the exact same md5sum result. These RF calibration values MUST be different, since they are used by the driver to output a flat response over the whole WiFi band, that cannot be guaranteed by the component tolerances. Having the same values for all the boards will result in sub-optimal performances and probably FCC/CE compliance failure. The ART partitions are 64kB long, but actually only a small part of it is used, from offset 0x1000 to 0x1440, and they don't contain the MAC address: this one is stored at the end of the U-Boot partition, at offset 0x0001fc00 on my boards. -- Michel _______________________________________________ openwrt-devel mailing list openwrt-devel@lists.openwrt.org https://lists.openwrt.org/cgi-bin/mailman/listinfo/openwrt-devel
