u-blox ZED-F9P Integration Manual

ZED-F9P-Integration Manual
UBX-18010802 - R02

4 Receiver description Page 40 of 114
Advance Information
Figure 26: MGA architecture
The data returned by the AssistNow Online Service is a sequence of UBX-MGA messages, starting
with an estimate of the current time in the form of a UBX-MGA-INI-TIME_UTC message.
AssistNow Online currently supports GPS, GLONASS, BeiDou, Galileo, and QZSS.
Customers may choose to use third party sources of assistance data instead of using the
AssistNow Online Service. Customers choosing this option will need to ensure that the data is
converted from the format used by the third party source to the appropriate MGA messages.
However, it is important to ensure that the receiver has an estimate of the current time
before it processes any other assistance data. For this reason, it is strongly recommended
to send a UBX-MGA-INITIME_ UTC or UBX-MGA-INI-TIME_GNSS as the first message of any
assistance.
4.6.2 Host software
As u-blox receivers have no means to connect directly with the Internet, the AssistNow Online
system can only work if the host system that contains the receiver can connect to the Internet,
download the data from the AssistNow Online Service and forward it on to the receiver. In the
simplest case that may involve fetching the data from the AssistNow Online Service (by means of
a single HTTP GET request), and sending the resulting data to the receiver.
Depending on the circumstances, it may be beneficial for the host software to include:
• Creating an appropriate UBX-MGA-INI-TIME_UTC message to deliver a better sense of time to
the receiver, especially if the host system has a very good sense of the current time and can
deliver a time pulse to one of the receiver's EXTINT pins.
• Enable and use flow control to prevent loss of data due to buffer overflow in the receiver.
u-blox provides the source code for an example library, called libMGA, that provides all of the
functionality we expect in most host software.
4.6.3 AssistNow Online sequence
A typical sequence of use of the AssistNow Online Service comprises the following steps:
• Power-up the u-blox receiver
• Request data from the AssistNow Online Service

u-blox ZED-F9P Specifications

General

GNSS	GPS, GLONASS, Galileo, BeiDou, QZSS, SBAS
Concurrent GNSS	4
RTK	Yes
Velocity Accuracy	0.05 m/s
Time Pulse Accuracy	30 ns
Operating Temperature	-40°C to +85°C
Supply Voltage	2.7 V to 3.6 V
Channels	184
Frequency Bands	L1, L2
Dimensions	22 mm x 17 mm x 2.4 mm
Interfaces	UART, SPI, I2C