ATR0635 Datasheet, PDF (13/33 Pages) ATMEL Corporation – ANTARIS4 Single-chip GPS Receiver SuperSense

ATR0635
3.3.2 Sensitivity Settings
Table 3-5. GPS Sensitivity Settings
GPSMODE3
(Fixed PU)
0⁽¹⁾
0⁽¹⁾
1⁽²⁾
1⁽²⁾
GPSMODE2
(Reset = PU) Description
0
Auto mode (Default ROM value)
1⁽²⁾
Fast mode
0
Normal mode
1⁽²⁾
High sensitivity
Notes: 1. Increased back-up current
2. Leave open
For all GPS receivers the sensitivity depends on the integration time of the GPS signals. There-
fore there is a trade-off between sensitivity and the time to detect the GPS signal (Time to first
fix). The three modes, “Fast Acquisition”, “Normal” and “High Sensitivity”, have a fixed integra-
tion time. The “Normal” mode, recommended for the most applications, is a trade off between
the sensitivity and TTFF. The “Fast Acquisition” mode is optimized for fast acquisition, at the
cost of a lower sensitivity. The “High Sensitivity” mode is optimized for higher sensitivity, at the
cost of longer TTFF. The “Auto” mode adjusts the integration time (sensitivity) automatically
according to the measured signal levels. That means the receiver with this setting has a fast
TTFF at strong signals, a high sensitivity to acquire weak signals but some times at medium sig-
nal level a higher TTFF as the “Normal” mode. These sensitivity settings affect only the startup
performance not the tracking performance.
3.4 Serial I/O Configuration
The ATR0635 features a two-stage I/O-message and protocol-selection procedure for the two
available serial ports. At the first stage, a certain protocol can be enabled or disabled for a given
USART port or the USB port. Selectable protocols are RTCM, NMEA and UBX. At the second
stage, messages can be enabled or disabled for each enabled protocol on each port. In all con-
figurations described below, all protocols are enabled on all ports, but output messages are
enabled in a way that ports appear to communicate at only one protocol. However, each port will
accept any input message in any of the three implemented protocols
Table 3-6. Serial I/O Configuration
GPSMODE12
(Reset = PU)
0
GPSMODE6
(Reset = PU)
0
USART1/USB
USART2
GPSMODE5 (Output Protocol/ (Output Protocol/
(Reset = PD) Baud Rate (kBaud)) Baud Rate (kBaud)) Messages⁽¹⁾ Information Messages
0⁽²⁾
UBX/57.6
NMEA/19.2
High
User, Notice, Warning, Error
0
0
1
UBX/38.4
NMEA/9.6
Medium User, Notice, Warning, Error
0
1⁽²⁾
0⁽²⁾
UBX/19.2
NMEA/4.8
Low
User, Notice, Warning, Error
0
1⁽²⁾
1
–/Auto
–/Auto
Off
None
1⁽²⁾
0
0⁽²⁾
NMEA/19.2
UBX/57.6
High
User, Notice, Warning, Error
1⁽²⁾
0
1
NMEA/4.8
UBX/19.2
Low
User, Notice, Warning, Error
1⁽²⁾
1⁽²⁾
0⁽²⁾
NMEA/9.6
UBX/38.4
Medium User, Notice, Warning, Error
1⁽²⁾
1⁽²⁾
1
UBX/115.2
NMEA/19.2
Debug
All
Notes: 1. See Table 3-7 to Table 3-10 on page 14, the messages are described in the ANTARIS4 protocol specification
2. Leave open
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4928C–GPS–06/06