ZED-F9T - Integration Manual
3.3.11.5.2 Write access
The receiver does not provide any write access except for writing UBX and NMEA messages to the
receiver, such as configuration or aiding data. Therefore, the register set mentioned in section Read
Access is not writeable. Following the start condition from the master, the 7-bit device address and
the
RW
bit (which is a logic low for write access) are clocked onto the bus by the master transmitter.
The receiver answers with an acknowledge (logic low) to indicate that it is responsible for the given
address. Now, the master can write 2 to
N
bytes to the receiver, generating a stop condition after the
last byte being written. The number of data bytes must be at least 2 to properly distinguish from
the write access to set the address counter in random read accesses.
Figure 16: DDC write access
3.4 Multiple GNSS assistance (MGA)
The u-blox MGA services provide a proprietary implementation of an A-GNSS protocol compatible
with u-blox GNSS receivers. When a client device makes an MGA request, the service responds
with the requested data using UBX protocol messages. These messages are ready for direct
transmission to the receiver communication port without requiring any modification by the client.
AssistNow Online optionally provides satellite ephemerides, health information and time aiding data
suitable for GNSS receiver systems with direct internet access.
The data downloaded from the service is organized by date and encoded into a sequence of UBX
MGA messages.
The ZED-F9T supports AssistNow Online only.
3.4.1 AssistNow Online
AssistNow Online is u-blox's end-to-end Assisted GNSS (A-GNSS) solution for receivers that have
access to the Internet. Data supplied by the AssistNow Online Service can be directly uploaded to
a u-blox receiver in order to substantially reduce time to first fix (TTFF), even under poor signal
conditions. The system works by collecting data such as ephemeris and almanac from the satellites
through u-blox's "Global Reference Network" of receivers and providing this data to customers in a
convenient form that can be forwarded directly to u-blox receivers.
The AssistNow Online Service uses a simple, stateless, HTTP interface. Therefore, it works on all
standard mobile communication networks that support Internet access, including GPRS, UMTS and
Wireless LAN. No special arrangements need to be made with mobile network operators to enable
AssistNow Online.
UBX-19005590 - R01
3 Receiver functionality
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