diff --git a/prod/doc/index.html b/prod/doc/index.html index ca0b826..a3a636c 100644 --- a/prod/doc/index.html +++ b/prod/doc/index.html @@ -68,7 +68,8 @@ Defective devices can be discarded or retained for a deeper analysis.
In this context, the actual process of soldering components to the unpopulated PCB, and all related tasks providing an input to this process. Such related tasks include the configuration of the - SMT line, and testing and conditioning of the components to solder. + SMT line, and testing and conditioning of the components prior to + soldering. @@ -114,12 +115,74 @@ Defective devices can be discarded or retained for a deeper analysis.

Fault analysis

-

Component orientation

+

Component placement and orientation

+ +

Supply voltages

+

Clock frequency

+The flawless performance of the crystal oscillator is crucial for +operation. Anomalies are easy to detect with even a low-cost oscilloscope +and pinpoint specific problems and help to select further analysis steps. +

+The crystal used in atben and atusb has a nominal tolerance +of +/- 15 ppm at 22-28 C. Low-cost oscilloscopes typically have a timing +accuracy of ++/- 100 ppm, which means that only major excursions can be detected by +measuring the clock output with such an instrument. Full-speed USB only +requires an accuracy of +/- 2500 ppm. +We can therefore consider all results within a range of +/- 1000 ppm as +sufficient, and perform more precise measurements by other means. This +applies to atben as well as to atusb. +

+ + +

Measuring the clock on atben

+ +atben normally does not output a clock signal. A 1 MHz clock +can be enabled with the following command: +
+atrf-txrx -d net:ben -C 1
+
+This configures atben as a promiscuous receiver. The reception +of any IEEE 802.15.4 frame or pressing Ctrl-C will terminate the command. +

+ +
ClockAction +
0 HzCheck voltages; check that the clock is enabled; + check for shorts around crystal; check connectivity of crystal +
0.999-1.001 MHz, ~3.3 VppPerform precision measurement with + atrf-xtal +
OtherCheck voltages; check for contamination around crystal +
+

+ + +

Measuring the clock on atusb

+ +The transceiver provides the clock for the microcontroller in atusb. +A clock signal is therefore always available. Immediately after reset, +the transceiver generates a 1 MHz clock. When the microcontrolled comes out +of reset, it raises the transceiver's clock output to 8 MHz and then +enables USB. +

+ +
ClockAction +
0 HzCheck voltages; check for shorts around crystal; check + connectivity of crystal +
0.999-1.001 MHz, ~3.3 VppCheck presence of firmware; check for + shorts on SPI signals; check connectivity of SPI signals +
7.992-8.008 MHz, ~3.3 VppPerform precision measurement with + atrf-xtal +
OtherCheck voltages; check for contamination around crystal +
+ + +

Precision measurements

+


-Last update: 2011-05-17  Werner Almesberger +Last update: 2011-05-18  Werner Almesberger