From 33f84b436c7458f11168ef0babb0d8aae440062b Mon Sep 17 00:00:00 2001 From: Werner Almesberger Date: Sat, 28 May 2011 13:19:45 -0300 Subject: [PATCH] prod/doc/: completed description of signal strength measurement - test.hmac: added more details on physical test setup - setup.hmac: described SPECTRUM_MARGIN parameter - setup.hmac: described process for generating the reference spectrum --- prod/doc/setup.hmac | 32 +++++++++++++++++++++++++++++++- prod/doc/test.hmac | 6 ++++++ 2 files changed, 37 insertions(+), 1 deletion(-) diff --git a/prod/doc/setup.hmac b/prod/doc/setup.hmac index c0fb4c6..be660fa 100644 --- a/prod/doc/setup.hmac +++ b/prod/doc/setup.hmac @@ -164,6 +164,11 @@ if the host name or IP address under which the Ben is reached differs from "ben", the value of ATBEN_DUT and ATUSB_REF will have be changed accordingly.

+The Makefile also contains the variable SPECTRUM_MARGIN that +defines how many dB of tolerance should be allowed below and above the +reference signal strength. The default is to allow a margin of 5 dB in +either direction. +

The scripts atusb and atusb-flash also contain configuration variables. If the names of the files containing the atusb firmware binaries are not boot.hex and @@ -369,7 +374,32 @@ Ben, and if a stable temperature is maintained. -@@@ +The signal strength of a DUT is assesses by comparing it with +measurements previously obtained in the same setup, with a known to +be good device taking the role of the DUT. It is therefore necessary +to establish a reference profile each time the test environment changes, +e.g., when changing location or when using a different reference device. +

+The physical arrangement of the devices should have the characteristics +described in the test section. The orientation +of the devices should be chosen such that the overall signal strength is +near its maximum, that the spectrum is relatively "flat", and that small +changes in the orientation only produce small variations in the measured +signal strength. +

+To generate the profiles for atben and atusb, simply run +

+make spectrum
+
+Then place the devices appropriately and press D in the measurement +window to use the displayed spectrum as the reference. Multiple spectra +can be merged into the reference, e.g., if environmental conditions cause +significant variations. Spectra included in the reference are shown in blue. +

+After a obtaining the reference spectrum, press Q to exit. The +Makefile will then record the signal strength limits for an atben +DUT in the file ben.profile and proceed with the reverse +measurement, i.e., with atusb acting as the DUT. diff --git a/prod/doc/test.hmac b/prod/doc/test.hmac index 73c5aa5..4d8b99d 100644 --- a/prod/doc/test.hmac +++ b/prod/doc/test.hmac @@ -29,6 +29,12 @@ the PC, insert the atben board into the Ben, and place both devices at the same location and with the same orientation used when acquiring the signal strength profile.

+The two devices should be about 1 m apart, with as few metal or watery +objects between or near them as possible. Location and orientation should +be easily reproducible, e.g., by marking the device's edges on the table +with tape. Other transmitters in the 2.4 GHz band will interfere with +measurements and should be kept as far away and as inactive as possible. +