3: Quick Start
GNSS Receiver Module A5135-H User Guide
17
3.2 Antenna
Although the A5135-H offers an on-module antenna, an additional external active
antenna can be used. Switching between both antennas is done via pin 12 (see also
“5.2Description A5135-H Signals”).
It is recommended to use an active GPS+GLONASS antenna with supply voltage of
3 to 5 VDC and a current draw of 50 mA maximum. The quality of the
GPS+GLONASS antenna chosen is off great importance to the overall sensitivity of
the GPS+GLONASS
system. An active antenna should have a gain ≥ 20 dB and a
n
oise figure ≤ 1.5 dB, which applies to more than 95% of the active antennas availa-
ble in the market.
3.3 Serial Port Settings
In UART operation (defined by the external pull-up resistor as outlined in Minimum
Configuration) the default serial port settings are:
•
NMEA, 9600 baudrate, 8 data bits, no parity, 1 stop bit, no flow control
3.4 Improved TTFF
In order to improve the TTFF (Time To First Fix), it is recommended to keep Vcc
supplied at all times. This will allow taking advantage of sophisticated low power
mode features of the SiRFstarV ROM chip set.
3.5 Self-start configuration
In order to minimize the GPIO required for operating A5135-H, WAKEUP (pin 4) and
ON_OFF (pin 19) can be tied together for entering the self-start mode such that no
ON_OFF pulse requires. Figure 7 shows the recommended connection for self-start
configuration with UART host port enabled.
Figure 7: Self-start configuration A5135-H
For self-start mode, full power operation will be activated once Vcc applied. No power
saving mode (PTF/MPM/Hibernation) will be supported.