ZED-F9K - Integration manual
Figure 19: 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 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.
3.7.4.1 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 or HTTPS GET request), and sending the resulting data to the receiver.
Depending on the circumstances, it may be beneficial for the host software to:
• Create an appropriate UBX-MGA-INI-TIME_UTC message to deliver a better estimation of the
current time to the receiver, especially if the host system has a very good estimation 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.
3.7.4.2 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.
UBX-20046189 - R01
3 Receiver functionality
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C1-Public
Early production information
