GLOBALSAT ET-314 GPS Engine Board - Manual (Page 8)

ET-314AC
High Performance GPS Engine Board
2010/4/1
- 8 -
OPERATING Description
VCC
This is the main power supply to the engine
board. (3.1Vdc to 3.5Vdc)
GND
This is Ground pin for the baseband circuit.
GND_A
This is Ground pin for the ET-314AC RFand
circuit. To use ET-314AC, GND_A need
connect to GND with L bead or 0Ω resistor.
RxD0
This is the main channel for receiving
software commands from SiRFdemo
software or from your proprietary software.
TxD0
This is the main transmits channel for
outputting navigation and measurement data
to user’s navigation software or user written
software. Output is TTL level, 0V ~ 2.85V
RxD1
For user’s application (default null).
TxD1
For user’s application (default null).
RF_IN
This pin receives signal of GPS analog via
external active antenna. It has to be a
controlled impedance trace at 50ohm. Do not
have RF traces closed the other signal path
and routing it on the top layer. Keep the RF
traces as short as possible.
V_BAT
This is the battery backup power input for the
SRAM and RTC when main power is off.
Without the external backup battery,
ET-314AC will always execute a cold star
after turning 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
3.5V.
NC
ET-314AC reserves PIN, Just NC.
VDD28OUT
This PIN is output voltage 2.85V. If do not
use it, Just NC.
RESET
This pin is input low active. This Module has
internal Power on Reset circuit.
GPIOs
User can use this I/O pin for special functions
(For example, control LED) .ET-314AC had
GPIO 1 & 13 &14.
VCC_RF
VCC_RF can supply Active Antenna Bias
voltage. This pin will supply Active Antenna.
If do not use it, Just NC.
V_ANT
V_ANT is Active Antenna Bias voltage input.
If you use Active Antenna, you can connect
this pin to VCC_RF or connect other POWER
(Vin = 2.85~5V). If you will be use Passive
Antenna, Just NC.
BOOTSEL
Set this pin to high for programming flash in
debug mode. If need programming
ET-314AC Flash, just pull-up 15KΩ resistor
to 3.3V. When ET-314AC used in normal
function, this pin just NC.
1PPS
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. If do not use it, Just NC.