EB-3531
Specifications are subject to be changed without notice.
Page 10 of 21
Version 1.2.1
Design Notes
VCC:
This is the main power supply to the engine board. (3.3Vdc ± 5%).
GND:
Ground pin for the baseband circuit.
RXA:
This is the main channel for receiving software commands from SiRFdemo software or
from your proprietary software.
RXB:
For user’s application (default null).
TXA:
This is the main channel for transmitting navigation and measurement data to a navigation
software or user written software. Output TTL level, 0V ~ 2.85V.
TXB:
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.
VBAT:
This is the battery backup power input for the SRAM and RTC when main power is
removed. Typically, the current draw is 15uA. Without the external backup battery, the
module/engine board 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 3.6v.
(
NOTE
:
When not in use 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 Rx
input to Zener’s cathode to pull the input “
HIGH
”.)
GPIO:
User can use this I/O pin for special functions. (For example, control LED).
BOOTSEL:
Set this pin to high for programming flash.
VCC_RF:
Provide Active Antenna Power 2.85V.
ON_OFF:
Edge triggered soft on/off request. It must be low for normal application.
GPIO15:
GPS status output. You can connect it to an LED.
Tracking:
Fixing: Hi
RF_PWR_CTRL:
RF power ON/OFF control. Hi: RF Power ON. Low: RF Power OFF.
