Ublox RCB-F9T Use and care manual

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RCB-F9T
u-blox RCB-F9T high accuracy timing board
Integration manual
Abstract
This document describes the features and application of RCB-F9T, a multi-
band GNSS timing board offering nanosecond level timing accuracy.
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RCB-F9T-Integration manual
Document information
Title RCB-F9T
Subtitle u-blox RCB-F9T high accuracy timing board
Document type Integration manual
Document number UBX-19003747
Revision and date R04 25-Feb-2020
Document status Early production information
This document applies to the following products:
Product name Type number Firmware version PCN reference
RCB-F9T RCB-F9T-0-01 TIM 2.01 UBX-19057484
u-blox reserves all rights to this document and the information contained herein. Products, names, logos and designs
described herein may in whole or in part be subject to intellectual property rights. Reproduction, use, modification or
disclosure to third parties of this document or any part thereof without the express permission of u-blox is strictly prohibited.
The information contained herein is provided "as is" and u-blox assumes no liability for the use of the information. No warranty,
either express or implied, is given with respect to, including but not limited to, the accuracy, correctness, reliability and fitness
for a particular purpose of the information. This document may be revised by u-blox at any time. For most recent documents,
please visit www.u blox.com.
Copyright © 2020, u-blox AG.
u-blox is a registered trademark of u-blox Holding AG in the EU and other countries.
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Contents
1 Integration manual structure............................................................................................ 5
2 System description...............................................................................................................6
2.1 Overview.................................................................................................................................................... 6
2.1.1 Differential timing.......................................................................................................................... 6
2.2 Architecture..............................................................................................................................................6
2.2.1 Block diagram..................................................................................................................................6
3 Receiver functionality.......................................................................................................... 7
3.1 Receiver configuration........................................................................................................................... 7
3.1.1 Changing the receiver configuration..........................................................................................7
3.1.2 Default GNSS configuration.........................................................................................................7
3.1.3 Default interface settings............................................................................................................ 8
3.1.4 Basic receiver configuration.........................................................................................................8
3.1.5 Differential timing mode configuration..................................................................................... 9
3.1.6 Legacy configuration interface compatibility........................................................................ 12
3.1.7 Navigation configuration............................................................................................................12
3.2 Geofencing..............................................................................................................................................16
3.2.1 Introduction...................................................................................................................................16
3.2.2 Interface......................................................................................................................................... 17
3.2.3 Geofence state evaluation......................................................................................................... 17
3.3 Interfaces................................................................................................................................................17
3.3.1 UART interface............................................................................................................................. 17
3.4 Predefined PIOs.....................................................................................................................................18
3.4.1 RESET_N........................................................................................................................................ 18
3.4.2 TIMEPULSE................................................................................................................................... 18
3.5 Antenna supervisor.............................................................................................................................. 18
3.5.1 Antenna voltage control - ANT_OFF........................................................................................18
3.5.2 Antenna short detection - ANT_SHORT_N............................................................................ 19
3.5.3 Antenna short detection auto recovery..................................................................................20
3.5.4 Antenna open circuit detection - ANT_DETECT................................................................... 20
3.6 Multiple GNSS assistance (MGA)..................................................................................................... 21
3.6.1 Authorization................................................................................................................................ 21
3.6.2 Multiple servers............................................................................................................................21
3.6.3 Preserving information during power-off................................................................................21
3.6.4 AssistNow Online......................................................................................................................... 22
3.7 Clocks and time.....................................................................................................................................25
3.7.1 Receiver local time.......................................................................................................................25
3.7.2 Navigation epochs....................................................................................................................... 26
3.7.3 iTOW timestamps........................................................................................................................26
3.7.4 GNSS times................................................................................................................................... 27
3.7.5 Time validity..................................................................................................................................27
3.7.6 UTC representation..................................................................................................................... 27
3.7.7 Leap seconds................................................................................................................................ 28
3.7.8 Real time clock............................................................................................................................. 29
3.7.9 Date.................................................................................................................................................29
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3.8 Timing functionality............................................................................................................................. 30
3.8.1 Time pulse..................................................................................................................................... 30
3.9 Security................................................................................................................................................... 33
3.9.1 Spoofing detection / monitoring...............................................................................................33
3.9.2 Jamming/interference indicator...............................................................................................34
3.9.3 GNSS receiver integrity.............................................................................................................. 34
3.10 u-blox protocol feature descriptions.............................................................................................. 35
3.10.1 Broadcast navigation data...................................................................................................... 35
3.11 Forcing a receiver reset.....................................................................................................................42
4 Design..................................................................................................................................... 43
4.1 Pin assignment......................................................................................................................................43
4.2 Power supply..........................................................................................................................................43
4.2.1 VCC: Main supply voltage.......................................................................................................... 43
4.2.2 RCB-F9T VCC_ANT: Antenna power supply.......................................................................... 44
4.3 Antenna...................................................................................................................................................44
4.4 EOS/ESD precautions.......................................................................................................................... 45
4.4.1 ESD protection measures.......................................................................................................... 45
4.4.2 EOS precautions...........................................................................................................................46
4.4.3 Safety precautions...................................................................................................................... 46
4.5 Electromagnetic interference on I/O lines.......................................................................................46
4.5.1 General notes on interference issues......................................................................................47
4.5.2 In-band interference mitigation................................................................................................47
4.5.3 Out-of-band interference........................................................................................................... 48
5 Product handling................................................................................................................. 49
5.1 ESD handling precautions.................................................................................................................. 49
Appendix.................................................................................................................................... 50
A RCB-F9T default configurations...........................................................................................................50
B Glossary......................................................................................................................................................50
Related documents................................................................................................................ 52
Revision history.......................................................................................................................53

RCB-F9T-Integration manual
1 Integration manual structure
This document provides a wealth of information to enable a successful design with the RCB-F9T
timing board. The manual is structured according to system, software and hardware aspects.
The first section, "System description" outlines the basics of the RCB-F9T timing board.
The following section "Receiver functionality" provides an exhaustive description of the receiver's
functionality. Beginning with the new configuration concept both existing and new users should read
this section to understand the new messages employed. Most of the following sub-sections should
be familiar to existing users of u-blox positioning products, however some changes are introduced
owing to the new configuration concept.
The sections from "Design" onwards addresses power supply recommendations and provides
information about the RCB-F9T hardware interfaces. An antenna section provides design
information and recommendation for this important component.
The final section addresses the major product handling concerns giving guidance on ESD
precautions.
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1 Integration
manual structure
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2 System description
2.1 Overview
The RCB-F9T timing board enables multi-band GNSS timing in a compact form factor using the
ZED-F9T, the u-blox F9 high accuracy timing module. The ZED-F9T module provides nanosecond
level timing accuracy in both standalone and differential timing modes.
In addition to the ZED-F9T module, the RCB-F9T timing board contains an SMB antenna connector
and 5 V power supply circuitry for an external active multi-band GNSS antenna. The 8-pin, 2.0 mm
pitch pin-header provides powering of the board, UART communications, and two independently
configurable time pulse signals.
2.1.1 Differential timing
The u-blox RCB-F9T high accuracy timing board takes local timing accuracy to the next level with
its differential timing mode.
In differential timing mode correction data is exchanged with other neighboring ZED-F9T timing
receivers via a communication network. In differential timing mode the RCB-F9T can operate either
as a master reference station, or as a slave station.
When RCB-F9T acts as a master reference timing station, it sends RTCM 3.3 differential corrections
to slave receivers.
When RCB-F9T acts as a slave receiver, it receives differential corrections RTCM 3.3 messages and
aligns its time pulse to the master reference station.
2.2 Architecture
The RCB-F9T timing board provides all the necessary RF and baseband processing to enable multi-
band GNSS timing. The block diagram below (Figure 1) shows the key functionality implemented in
the RCB-F9T.
2.2.1 Block diagram
Figure 1: RCB-F9T block diagram
An active antenna is mandatory with the RCB-F9T.
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3 Receiver functionality
This section describes the RCB-F9T operational features and their configuration.
3.1 Receiver configuration
The RCB-F9T is fully configurable with UBX configuration interface keys. The configuration
database in the receiver's RAM holds the current configuration, which is used by the receiver
at run-time. It is constructed on start-up of the receiver from several sources of configuration.
The configuration interface and the available keys are described fully in the RCB-F9T Interface
description [2].
The configuration interface has changed from earlier u-blox positioning receivers. There
is some backwards compatibility, however, users are strongly advised to adopt the
configuration interface described in this document. See legacy UBX-CFG message fields
reference section in the RCB-F9T Interface description [2].
Configuration interface settings are held in a database consisting of separate configuration items.
An item is made up of a pair consisting of a key ID and a value. Related items are grouped together
and identified under a common group name: CFG-GROUP-*; a convention used in u-center and
within this document. Within u-center, a configuration group is identified as "Group name" and the
configuration item is identified as the "item name" under the "Generation 9 Configuration View" -
"Advanced Configuration" view.
The UBX messages available to change or poll the configurations are the UBX-CFG-VALSET, UBX-
CFG-VALGET, and UBX-CFG-VALDEL messages. For more information about these messages and
the configuration keys see the configuration interface section in the RCB-F9T Interface description
[2].
3.1.1 Changing the receiver configuration
All configuration messages, including legacy UBX-CFG messages, will result in a UBX-ACK-ACK
or UBX-ACK-NAK response. If several configuration messages are sent without waiting for this
response then the receiver may pause processing of input messages until processing of a previous
configuration message has been completed. When this happens a warning message "wait for cfg
ACK" will be sent to the host.
3.1.2 Default GNSS configuration
The RCB-F9T default GNSS configuration is set as follows:
• GPS: L1C/A, L2C
• GLONASS: L1OF, L2OF
• Galileo: E1B/C, E5b
• BeiDou: B1I, B2I
• QZSS: L1C/A, L2C
SBAS is also supported but not enabled in the default GNSS configuration. SBAS is not
recommended for timing applications.
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For more information about default configuration, see the RCB-F9T Interface description [2].
3.1.3 Default interface settings
Interface Settings
UART Output 115200 baud, 8 bits, no parity bit, 1 stop bit. NMEA GGA, GLL, GSA, GSV, RMC, VTG, TXT (and
no UBX) messages are output by default.
UART Input 115200 baud, 8 bits, no parity bit, 1 stop bit. UBX, NMEA and RTCM 3.3 messages are enabled
by default.
Table 1: Default configurations
Refer to the u-blox RCB-F9T Interface description [2] for information about further
settings.
By default the RCB-F9T outputs NMEA 4.10 messages that include satellite data for all GNSS bands
being received. This results in a higher-than-before NMEA load output for each navigation period.
Make sure the UART baud rate being used is sufficient for the selected navigation rate and the
number of GNSS signals being received.
3.1.4 Basic receiver configuration
This section summarizes the basic receiver configuration most commonly used.
3.1.4.1 Message output configuration
The rate of NMEA, UBX and RTCM protocol output messages are configurable.
If the rate configuration value is zero, then the corresponding message will not be output. Values
greater than zero indicate how often the message is output.
For periodic output messages the rate relates to the event the message is related to. For example,
the UBX-NAV-PVT (navigation position velocity and time solution) is related to the navigation epoch.
If the rate of this message is set to one (1), it will be output for every navigation epoch. If the rate
is set to two (2), it will be output every other navigation epoch. The rates of the output messages
are individually configurable per communication interface. See the CFG-MSGOUT-* configuration
group.
Some messages, such as UBX-MON-VER, are not periodic and will only be output as an answer to
a poll request.
The UBX-INF-* and NMEA-Standard-TXT information messages are non-periodic output messages
that do not have a message rate configuration. Instead they can be enabled for each communication
interface via the CFG-INFMSG-* configuration group.
All message output is additionally subject to the protocol configuration of the
communication interfaces. Messages of a given protocol will not be output until the protocol
is enabled for output on the interface (see the previous section).
3.1.4.2 GNSS signal configuration
The GNSS constellations and bands are configurable with configuration keys from configuration
group CFG-SIGNAL-*. Each GNSS constellation can be enabled or disabled independently. A GNSS
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constellation is considered to be enabled when the constellation enable key is set and at least one
of the constellation's band keys is enabled.
3.1.5 Differential timing mode configuration
In differential timing mode the RCB-F9T can operate either as a master reference station or as a
slave station. Using the RTCM3 protocol, the master sends timing corrections to the slave via a
communication link enabling the slave to compute its time relative to the master with high accuracy.
This section describes how to configure the RCB-F9T high accuracy timing board as a master
reference station and as slave station. The section begins with a note describing the RTCM protocol
and corresponding supported message types.
3.1.5.1 RTCM corrections
RTCM is a binary data protocol for communication of GNSS correction information. The RCB-F9T
high accuracy timing board supports RTCM as specified by RTCM 10403.3, Differential GNSS
(Global Navigation Satellite Systems) Services – Version 3 (October 7, 2016).
The RTCM specification is currently at version 3.3 and RTCM version 2 messages are not supported
by this standard.
To modify the RTCM input/output settings, see the configuration section in the u-blox RCB-F9T
Interface description [2].
3.1.5.2 List of supported RTCM input messages
Message Description
RTCM 1005 Stationary RTK reference station ARP
RTCM 1077 GPS MSM7
RTCM 1087 GLONASS MSM7
RTCM 1097 Galileo MSM7
RTCM 1127 BeiDou MSM7
RTCM 1230 GLONASS code-phase biases
RTCM 4072.1 Additional reference station information
Table 2: RCB-F9T supported input RTCM version 3.3 messages
3.1.5.3 List of supported RTCM output messages
Message Description
RTCM 1005 Stationary RTK reference station ARP
RTCM 1077 GPS MSM7
RTCM 1087 GLONASS MSM7
RTCM 1097 Galileo MSM7
RTCM 1127 BeiDou MSM7
RTCM 1230 GLONASS code-phase biases
RTCM 4072.1 Additional reference station information
Table 3: RCB-F9T supported output RTCM version 3.3 messages
3.1.5.4 Timing receiver position
Time mode is a special receiver mode where the position of the receiver is known and fixed and only
the time and frequency is calculated using all available satellites. This mode allows for maximum
time accuracy, for single-SV solutions, and also for using the receiver as a stationary reference
station.
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In order to use time mode, the receiver's position must be known as exactly as possible. Errors in the
fixed position will translate into time errors depending on the satellite constellation.
The following procedures can be used to initialize the timing receiver position:
• Using built-in survey-in procedure to estimate the position.
• Entering coordinates independently generated or taken from an accurate position such as a
survey marker.
3.1.5.4.1 Survey-in
Survey-in is a procedure that is carried out prior to entering Time mode. It estimates the receiver
position by building a weighted mean of all valid 3D position solutions.
Two major parameters are required when configuring:
• A minimum observation time defines the minimum observation time independent of the
actual number of fixes used for the position estimate. Values can range from one day for high
accuracy requirements to a few minutes for coarse position determination.
• A 3D position standard deviation defines a limit on the spread of positions that contribute to
the calculated mean.
Survey-in ends when both requirements are successfully met. The Survey-in status can be queried
using the UBX-TIM-SVIN message.
The timing receiver should not be fed RTCM corrections while it is in survey-in mode.
To configure a timing receiver into Survey-in mode (CFG-TMODE-MODE=SURVEY_IN), the following
items are required:
Configuration item Description
CFG-TMODE-MODE Receiver mode (disabled, survey-in or fixed)
CFG-TMODE-SVIN_MIN_DUR Survey-in minimum duration
CFG-TMODE-SVIN_ACC_LIMIT Survey-in position accuracy limit. The accuracy of given coordinates in 0.0001
meters (i.e. value 100 equals 1 cm)
Table 4: Configuration items used for setting a timing receiver into Survey-in mode
Set the configuration items shown above into flash memory to perform a survey-in
procedure automatically upon start-up.
3.1.5.4.2 Fixed position
Here the timing receiver position coordinates are entered manually. Any error in the timing receiver
position will directly translate into timing errors.
To configure into Fixed mode (CFG-TMODE-MODE=FIXED), the following items are relevant:
Once the receiver is set in fixed mode, select the position format to use: either LLH or ECEF with
optional high precision (mm) coordinates compared to the standard cm value.
For example, with CFG-TMODE-POS_TYPE=ECEF the timing receiver antenna position can be
entered to cm precision using CFG-TMODE-ECEF_X, CFG-TMODE-ECEF_Y, CFGTMODE-ECEF_Z.
For high precision (mm) coordinates use CFG-TMODEECEF_X_HP, CFG-TMODE-ECEF_Y_HP, CFG-
TMODE-ECEF_Z_HP. The same applies with corresponding coordinates used with CFG-TMODE-
POS_TYPE=LLH.
If the timing receiver is moved during operation then new position coordinates must be
configured.
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