V1.4
– Apr-13
User’s Manual
Page 29 of 34
titled “Set TricklePower Parameters”. In order to request a fix outside the specified
duty cycles, it is necessary to toggle the ON_OFF pin. Toggling is done by pulling the
signal to HIGH for about 200ms.
9.5 Hibernate Mode
In order to enter Hibernate Mode it is necessary to send a shutdown command or to
toggle to ON_OFF pin by pulling the signal to HIGH for about 200ms. Starting with
firmware version 4.0.1 the according command is supported in NMEA and SiRF
Binary mode. After a short delay the module will switch into hibernate mode. The
RTC will keep on running and SRAM is backed with the typical current of 20 μA
drawn from Vcc. To wake the module up again, toggling the ON_OFF pin is neces-
sary (200ms pulse width).
9.6 Extended Ephemeris
The receiver is capable of supporting two versions of using Extended Ephemeris (EE)
data. The first one is the version, where the EE data are calculated on a server, are
transmitted to device incorporating the receiver, and are then loaded into the receiver.
These data can be valid for up to seven days.
The second version is the internal extrapolation of available “natural” Ephemeris data.
This is done automatically and no external support is required. The internally calc u-
lated EE data are valid for up to 3 days.
The receiver firmware will define which set of EE data to use or will neglect those in
case “natural” data are available. Both versions of EE data will help to further lower
power consumption in SiRFaware
TM
mode.
9.7 TM_GPIO5 pin (1 pulse per second pin)
The 1PPS pin is an output pin.
In addition to precise positioning, GPS also allows for accurate timing due to the
synchronized atomic clocks in the GPS satellites. While the current date and time is
transmitted in NMEA sentences (UTC), an exact and accurate timing signal is pro-
vided via the 1PPS pin of the A2035-H GPS receiver.
Under good signal conditions the 1PPS signal comes between 620ns and 710ns
after the full GPS system second which is accurately (around 10ns) synchronized to
UTC. Therefore the 1 second clock can be derived and maintained within around
90ns under good signal conditions.
Note:
The 1PPS clock accuracy directly depends on the position accuracy!
The GPS signals travel at the speed of light, therefore a position inaccuracy directly
translates into 1PPS inaccuracies.
