ZOE-M8B - System Integration Manual
UBX-17045131 - R04
Contents
Page 15 of 42
Production Information
2.1.2.2
Continuous Mode
Continuous Mode provides the best performance in terms of tracking sensitivity and navigation
performance by acquiring all satellites that are visible in the sky. Continuous mode uses the
acquisition engine until all visible satellites are acquired, and uses the tracking engine to track the
satellites.
In order to achieve the best navigation performance, the tracking engine is not duty-cycled.
If balanced operation is selected for the continuous mode, then some GNSS RF operations are
optimized. This reduces the power consumption slightly for the tracking phase.
The navigation update rate in the continuous mode is set with the UBX-CFG-RATE message.
2.2
Communication interfaces
The ZOE-M8B GNSS SiP provides UART, SPI and DDC (I
2
C compatible) interfaces for communication
with a host CPU. Additionally, an SQI interface is available for connecting the ZOE-M8B GNSS SiP with
an optional external flash memory.
The UART, SPI and DDC pins are supplied by
VCC
and operate at this voltage level.
Four dedicated pins can be configured as either 1 x UART and 1 x DDC or a single SPI interface
selectable by
D_SEL
pin. Table 2 below provides the port mapping details.
Pin #
Pin D4 (D_SEL) = “high” (left open)
Pin D4 (D_SEL) = “Low” (connected to GND)
J5
UART TXD
SPI MISO
J4
UART RXD
SPI MOSI
B1
DDC SCL
SPI CLK
A2
DDC SDA
SPI CS_N
Table 2: Communication Interfaces overview
☞
It is not possible to use the SPI interface simultaneously with the DDC or UART interface.
☞
For debugging purposes, it is recommended to have a second interface e.g. DDC available that is
independent from the application and accessible via test-points.
For each interface, a dedicated pin can be defined to indicate that data is ready to be transmitted.
The TXD Ready signal indicates that the receiver has data to transmit. Each TXD Ready signal is
associated with a particular interface and cannot be shared. A listener can wait on the TXD Ready
signal instead of polling the DDC or SPI interfaces. The UBX-CFG-PRT message lets you configure
the polarity and the number of bytes in the buffer before the TXD Ready signal goes active. The TX
Ready signal can be mapped e.g. to UART TX. The TXD Ready function is disabled by default.
☞
The TXD Ready functionality can be enabled and configured by proper AT commands sent to the
involved u-blox cellular module supporting the feature. For more information see the
GPS
Implementation and Aiding Features in u-blox wireless modules [2].
☞
The TXD Ready feature is supported on several u-blox cellular module products.
2.2.1
UART interface
A UART interface is available for serial communication to a host CPU. The UART interface supports
configurable data rates with the default at 9600 baud. Signal levels are related to the
VCC
supply
voltage. An interface based on RS232 standard levels (+/- 7 V) can be realized using level shifter ICs
such as the Maxim MAX3232.
Hardware handshake signals and synchronous operation are not supported.
