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diff --git a/usr.sbin/xntpd/gadget/README b/usr.sbin/xntpd/gadget/README deleted file mode 100644 index 35bbc18..0000000 --- a/usr.sbin/xntpd/gadget/README +++ /dev/null @@ -1,84 +0,0 @@ -Gadget Box - -The gadget box is a 5"x3"x2" aluminum minibox containing level-converter -and modem circuitry and intended for use with host time servers -supporting the Network Time Protocol. It includes two subcircuits. One -of these converts a TTL positive edge into a fixed-width pulse at EIA -levels and is for use with a timecode receiver or oscillator including a -TTL one-pulse-per-second (1-pps) output. The other converts the timecode -modulation broadcast by Canadian time/frequency standard station CHU -into a 300-bps serial character stream at EIA levels and is for use with -the clk_chu.c or clk_chu_STREAMS.c modules in the xntp3 distribution. - -This archive contains complete construction details for the gadget box, -including schematic, parts list and artwork for a two-sided, printed- -circuit board. All files are in PostScript, with the exception of this -file and an information file, which are in ASCII. The artwork is in the -1:1 scale and is suitable for direct printing on photographic resist for -each side of the board. While a plated-through-holes process is most -convenient, it is possible to bridge the two sides using soldered wires -where necessary. - -Following is a brief functional description of the device. See the -schematic diagram gadget.s01 for reference. The audio output of a -shortwave radio tuned to CHU at 3330, 7335 or 14670 kHz is connected to -J2. A level of at least 30 mV peak-peak is required, such as provided by -the recorder output on many receivers. The input level is adjusted by -potentiometer R8 so that the timecode modulation broadcast at 31-39 -seconds past the minute reliably lights green LED1, but the signals -broadcast during other seconds of the minute do not. - -Opamp U4A provides low-impedance drive for the bridged-tee bandpass -filter U4B. The filter has a bandpass of about 600 Hz at the 6-dB points -and a center frequency of about 2150 Hz. It is designed to avoid -aliasing effects with receivers of relatively wide bandpass -characteristics. The modem itself is implemented by U2 and its -associated circuitry. Resistors R4 and R1 are a 40-dB pad which matches -the filter output to the modem input. U2 is a TTL/EIA level converter -with integral power supply for bipolar signals. The modem output is -available at pin 3 (receive data) of DB25 connector J1. - -The TTL 1-pps signal is connected via J3 to a retriggerable one-shot -U3A, which generates a TTL pulse of width determined by potentiometer -R7. The pulse width is determined by the bit rate of the attached serial -port. In the common case the width is one bit-time, such as 26 us for -38.4 kbps, for example. This appears to the port as a single start bit -of zero followed by eight bits of ones and a stop bit of one. The second -one-shot U3B generates a 200-ms pulse suitable for driving the amber -LED3 as a visual monitor. The output of U3A is converted to EIA levels -by U1 and appears at pin 12 (secondary receive data) of J1. - -If only the 1-pps circuit is required, U2 and U4 can be deleted and the -gadget box powered from the EIA modem-control signal at pin 20 (terminal -ready) of J1, assuming this signal is placed in the on (positive -voltage) condition by the computer program. J1 is wired to keep most -finicky UARTs and terminal-driver programs happy. If the CHU circuit is -required, an external 12-volt AC transformer or 9-12-volt DC supply -connected to J4 is required. Red LED2 indicates power is supplied to the -box. - -Following is a list of files included in this archive. All files are in -PostScript, except this one (README) and the information file -(gadget.lst), which are in ASCII. The files gadget.s01, gadget.s02 and -gadget.lst were generated using the Schema schematic-capture program -from Omation. The printed-circuit files *.lpr were generated using -Schema-PCB, also from Omation. - -Files ----------------------------------------- -README this file -gadget.s01 circuit schematic -gadget.s02 minibox assembly drawing -gadget.lst net list, pin list, parts list, etc. -gen0102.lpr pcb x-ray diagram -art01.lpr pcb artword side 1 -art02.lpr pcb artwork side 2 -adt0127.lpr pcb assembly drawing -dd0124.lpr pcb drill drawing -sm0228.lpr pcb solder mask (side 2) -sst0126.lpr pcb silkscreen mask (side 1) - -Dave Mills -University of Delaware -6 July 1992 -Revised 21 August 1992 |
