ET-318
Specifications are subject to be changed without notice.
Page 5 of 16
Version 1.3.1
Pin Explanation
VCC_IN
This is the main DC supply for a 3.3V +- 5% DC input power module board.
GND
GND provides the ground for digital part.
BOOTSEL
Set this pin to high for programming flash.
RXA
This is the main receiver channel and is used to receive software commands to the board from SIRFdemo
software or from user written software. Pull up if not used.
RXB
This is the auxiliary receiving channel and is used to input differential corrections to the board to enable
DGPS navigation. Pull up if not used.
TXA
This is the main transmitting channel and is used to output navigation and measurement data to
SiRFdemo or user written software.
TXB
For user’s application (not currently used).
RF_IN
This pin receiver signal of GPS analog .due to the RF characteristics of the signal the design has to certain
criteria. The line on the PCB from the antenna (or antenna connector) has to be a controlled microstrip line
at 50
Ω
.
PPS
This pin provides one pulse-per-second output from the board, which is synchronized to GPS time. This is
not available in Trickle Power mode.
VBAT (memory Back-up)
This is the battery backup input that powers the SRAM and RTC when main power is removed. Typical
current draw is 15uA. Without an external backup battery, the module/engine board will execute a cold star
after every turn on. To achieve the faster start-up offered by a hot or warm start, a battery backup must be
connected. The battery voltage should be between 2.0v and 5.0v.
(
NOTE
:
This pin must be kept “
HIGH
” for
operation. From Vcc connect a 470 Ohm resistor in series with a 3.2v Zener diode to Ground. Then, connect the VBAT input to
Zener’s cathode to pull the input “
HIGH
”.)
TIMEMARK
This pin provides one pulse-per-second output from the board, which is synchronized to GPS time. This is
not available in Trickle Power mode.
