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messages will always produce a response. This will be UBX-ACK-NAK in case of error, otherwise UBX-
ACK-ACK unless there is some other defined response to the message.
It is possible to send a small number of logging commands without waiting for acknowledgment,
since there is a command queue, but this risks confusion between the acknowledgments for the
commands. Also a command queue overflow would result in commands being lost.
3.5 Communication Interface
u-blox receivers are equipped with a communication interface which is multi-protocol capable. The
interface can be used to transmit GNSS measurements, monitor status information and configure
the receiver.
More than one protocol (e.g. UBX protocol and NMEA) can be assigned to a single port (multi-
protocol capability), which is particularly useful for debugging purposes.
RCB-F9T provides a UART interface for communication with a host CPU. The interface is configured
via the configuration methods described in the applicable interface description [2]
The following table shows the port number reported in the UBX-MON-COMMS messages.
Port no.
UBX-MON-COMMS portId
1
0x0100
Table 17: Port number assignment
It is important to isolate interface pins when the RCB-F9T VCC is removed. They can be
allowed to float or connected to a high impedance.
3.5.1 UART
The UART serves as the host interface. It supports a configurable baud rate and protocol selection.
The default baud rate is 115200 baud. To prevent buffering problems it is recommended
not to run at a lower baud rate than 38400 baud.
3.6 Predefined PIOs
In addition to the communication ports, there are some predefined PIOs provided by RCB-F9T to
interact with the receiver. These PIOs are described in this section.
If hardware backup mode is used a proper isolation of the interfaces is needed.
3.6.1 RESET_N
The RCB-F9T provides the ability to reset the receiver. The RESET_N pin is an input-only pin with an
internal pull-up resistor. Driving RESET_N low for at least 100 ms will trigger a cold start.
The RESET_N pin will delete all information and trigger a cold start. It should only be used
as a recovery option.
3.6.2 TIMEPULSE
The RCB-F9T provides time pulse signals on the TIMEPULSE and TIMEPULSE2 pins.
More information about the time pulse feature and its configuration can be found in the
section.
UBX-22004121 - R01
C1-Public
Electrical interface
UART1
3 Receiver functionality
Early production information
RCB-F9T - Integration manual
Time pulse
Page 26 of 64
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