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189 lines
5.7 KiB
HTML
189 lines
5.7 KiB
HTML
<TITLE>Production and testing</TITLE>
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<BODY>
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<HTML>
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<H1>Production and testing</H1>
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This document gives a high-level description of the production test process
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for <B>atben</B> and <B>atusb</B> boards, plus - in the case of <B>atusb</B>
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the production steps required between the boards leaving the SMT line and the
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actual testing.
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<P>
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The testing serves two purposes:
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<OL>
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<LI>Ascertain the correctness of the preceding production steps, and
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<LI>identify suffering from random production flaws and either discard
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them or prepare them for repair.
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</OL>
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The results of testing and fault analysis also provide feedback for the
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SMT process and steps preceding it.
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<P>
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The following diagram illustrates the workflow:
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<P>
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<IMG src="flow.png">
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<P>
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Only <B>atusb</B> boards contain firmware and need flashing (which is
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a two-step process, see below). The functional tests and further fault
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analysis are largely the same for <B>atben</B> and <B>atusb</B>.
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<P>
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Devices accepted for further use can then be packaged for shipping.
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Defective devices can be discarded or retained for a deeper analysis.
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<H2>Terminology</H2>
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<DL>
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<DT>Ben</DT>
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<DD>a device capable of hosting the <B>atben</B> and <B>atusb-pgm</B>
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boards. In the production process, a Ben can perform three different
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roles:
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<OL>
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<LI> Host an <B>atben</B> board acting as DUT
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<LI> Host an <B>atben</B> board acting as reference
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<LI> Host an <B>atusb-pgm</B> used for flashing the boot loader
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</OL>
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In this document, we assume that a single Ben is used in all
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three roles, with the board in its 8:10 card slot changed as
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the role requires.
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<DT>PC</DT>
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<DD>a device capable of connecting to a Ben via USB, and of hosting an
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<B>atusb</B> board. In the production process, a PC can perform three
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different roles:
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<OL>
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<LI> Host an <B>atusb</B> board acting as DUT
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<LI> Host an <B>atusb</B> board acting as reference
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<LI> Control a Ben via USB (for convenience)
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</OL>
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In this document, we assume that a single PC is used in all
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three roles, with one USB host port permanently connecting to the
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Ben, and a second USB host port populated with <B>atusb</B> boards
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as needed.
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<DT>DUT</DT>
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<DD>Device Under Test. An <B>atben</B> or <B>atusb</B> board that
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has left SMT, and is being prepared for testing or in the process
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of being tested.
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<DT>Reference</DT>
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<DD>An <B>atben</B> or <B>atusb</B> device that is known to work and
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and that acts as a peer for RF communication with the DUT.
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<DT>SMT</DT>
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<DD>In this context, the actual process of soldering components to
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the unpopulated PCB, and all related tasks providing an input to
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this process. Such related tasks include the configuration of the
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SMT line, and testing and conditioning of the components prior to
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soldering.
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</DL>
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<H2>Setup</H2>
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<H3>PC software installation</H3>
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<H3>Ben software installation</H3>
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<H3>Ben software setup</H3>
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<H3>Test profiles</H3>
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<H2>Flashing (atusb only)<H2>
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<H3>Flashing the boot loader</H3>
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<P>
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<IMG src="setup-C.png">
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<P>
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<H3>Flashing the application</H3>
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<P>
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<IMG src="setup-D.png">
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<P>
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<H2>Functional test</H2>
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<H3>Test setup for atben</H3>
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<P>
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<IMG src="setup-A.png">
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<P>
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<H3>Test setup for atusb</H3>
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<P>
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<IMG src="setup-B.png">
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<P>
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<H3>Test procedure</H3>
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<H2>Fault analysis</H2>
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<H3>Component placement and orientation</H3>
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<H3>Supply voltages</H3>
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<H3>Clock frequency</H3>
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The flawless performance of the crystal oscillator is crucial for
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operation. Anomalies are easy to detect with even a low-cost oscilloscope
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and pinpoint specific problems and help to select further analysis steps.
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<P>
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The crystal used in <B>atben</B> and <B>atusb</B> has a nominal tolerance
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of +/- 15 ppm at 22-28 C. Low-cost oscilloscopes typically have a timing
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accuracy of
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+/- 100 ppm, which means that only major excursions can be detected by
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measuring the clock output with such an instrument. Full-speed USB only
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requires an accuracy of +/- 2500 ppm.
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We can therefore consider all results within a range of +/- 1000 ppm as
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sufficient, and perform more precise measurements by other means. This
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applies to <B>atben</B> as well as to <B>atusb</B>.
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<P>
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<H4>Measuring the clock on atben</H4>
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<B>atben</B> normally does not output a clock signal. A 1 MHz clock
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can be enabled with the following command:
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<PRE>
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atrf-txrx -d net:ben -C 1
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</PRE>
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This configures <B>atben</B> as a promiscuous receiver. The reception
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of any IEEE 802.15.4 frame or pressing Ctrl-C will terminate the command.
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<P>
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<TABLE>
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<TR><TH align="left">Clock<TH align="left">Action
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<TR><TD>0 Hz<TD>Check voltages; check that the clock is enabled;
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check for shorts around crystal; check connectivity of crystal
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<TR><TD>0.999-1.001 MHz, ~3.3 Vpp<TD>Perform precision measurement with
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<B>atrf-xtal</B>
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<TR><TD>Other<TD>Check voltages; check for contamination around crystal
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</TABLE>
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<P>
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<H4>Measuring the clock on atusb</H4>
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The transceiver provides the clock for the microcontroller in <B>atusb</B>.
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A clock signal is therefore always available. Immediately after reset,
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the transceiver generates a 1 MHz clock. When the microcontrolled comes out
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of reset, it raises the transceiver's clock output to 8 MHz and then
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enables USB.
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<P>
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<TABLE>
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<TR><TH align="left">Clock<TH align="left">Action
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<TR><TD>0 Hz<TD>Check voltages; check for shorts around crystal; check
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connectivity of crystal
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<TR><TD>0.999-1.001 MHz, ~3.3 Vpp<TD>Check presence of firmware; check for
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shorts on SPI signals; check connectivity of SPI signals
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<TR><TD>7.992-8.008 MHz, ~3.3 Vpp<TD>Perform precision measurement with
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<B>atrf-xtal</B>
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<TR><TD>Other<TD>Check voltages; check for contamination around crystal
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</TABLE>
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<H4>Precision measurements</H4>
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<P>
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<HR>
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Last update: 2011-05-18 <I>Werner Almesberger</I>
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<HR>
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</BODY>
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</HTML>
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