Trimble Outdoors SK8 - Manual (Page 29)

Lassen-SK8 Embedded GPS Module 1-7
Starter Kit
The interface motherboard includes a 9 to 32 VDC switching power supply which
provides a regulated +5 VDC to the receiver. It also converts the TTL-level I/O to RS-232
for a direct interface to a computer. The motherboard provides an open-collector interface
for the PPS and also includes a 3.6V lithium backup battery enabling lightening-fast hot
starts. The Starter Kit includes an AC/DC converter for powering the module from an AC
wall socket. The metal enclosure (see Figure 1-3) provides 2 interface port connectors, an
antenna connector and a power connector. The mounting plate is secured to the metal
enclosure with four screws. The eight pin header plugs into the corresponding 8-pin socket
on the motherboard as shown in Figure 1-3.
Figure 1-3. Starter Kit Interface Unit
*
Note – Due to the open-collector interface, the polarity of the PPS signal is inverted. The
pulse is a 10µs negative-going pulse with the falling edge synchronized to UTC. When
removed from the motherboard, the receiver provides a TTL level, positive-going pulse. In
order to pull up the 1pps use a 10k pull up resister as shown in the following illustration.
.
Figure 1-4. Open Collector PPS
The Starter Kit interface unit provides fifty percent of the duty cycle on the PPS line.
•
PORT 1
+5
Vdc
Pin 9
PPS
Pin 9
10K ohm