Ublox C94-M8P User manual

C94-M8P
u-blox RTK Application Board Package
User Guide
Abstract
This document describes the structure and use of the C94-M8P RTK
application board package and provides information for evaluating
and testing the u-blox NEO-M8P high precision positioning
modules.
www.u-blox.com
UBX-15031066 - R06

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Document Information
Title
C94-M8P
Subtitle
u-blox RTK Application Board Package
Document type
User Guide
Document number
UBX-15031066
Revision and date
R06
01-Feb-2017
Document status
Advance Information
Document status explanation
Objective Specification
Document contains target values. Revised and supplementary data will be published later.
Advance Information
Document contains data based on early testing. Revised and supplementary data will be published later.
Early Production Information
Document contains data from product verification. Revised and supplementary data may be published later.
Production Information
Document contains the final product specification.
This document applies to the following products:
Product name
Type number
Firmware/FLASH version
PCN reference
C94-M8P
C94-M8P-1-10
FLASH FW3.01 HPG1.30
N/A
C94-M8P
C94-M8P-2-10
FLASH FW3.01 HPG1.30
N/A
C94-M8P
C94-M8P-3-10
FLASH FW3.01 HPG1.30
N/A
C94-M8P
C94-M8P-4-10
FLASH FW3.01 HPG1.30
N/A
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, including but not limited, with respect 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 © 2017, u-blox AG

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Preface
Using this guide
This guide assumes, the user has basic computer skills and is familiar with the Windows Graphical User Interface
(GUI) and GNSS receiver environments.
The following symbols are used in the document to highlight information:
A warning symbol indicates actions that could negatively impact or damage the device.
An index finger points out key information pertaining to device operation and performance.
Warnings and certifications
CAUTION! IN THE UNLIKELY EVENT OF A FAILURE IN THE INTERNAL PROTECTION
CIRCUITRY THERE IS A RISK OF AN EXPLOSION WHEN CHARGING FULLY OR
PARTIALLY DISCHARGED BATTERIES. REPLACE THE BATTERY IF IT NO LONGER
HAS SUFFICIENT CHARGE FOR UNIT OPERATION. CONTROL THE BATTERY BEFORE
USING IF THE DEVICE HAS NOT BEEN OPERATED FOR AN EXTENDED PERIOD OF
TIME.
Products marked with this lead-free symbol on the product label comply with the
“Directive 2002/95/EC and Directive 2011/65/EU of the European Parliament and the
Council on the Restriction of Use of certain Hazardous Substances in Electrical and
Electronic Equipment” (RoHS).
C94-M8P application board is RoHS compliant.

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Contents
Preface ................................................................................................................................3
Using this guide............................................................................................................................................... 3
Warnings and certifications ............................................................................................................................. 3
Contents..............................................................................................................................4
1Introduction..................................................................................................................6
1.1 Overview .............................................................................................................................................. 6
1.2 C94-M8P package includes .................................................................................................................. 6
1.3 Software requirements ......................................................................................................................... 6
1.4 System requirements ............................................................................................................................ 6
2Specification .................................................................................................................7
3Getting started .............................................................................................................8
3.1 Software installation ............................................................................................................................. 8
3.2 Hardware installation............................................................................................................................ 8
3.2.1 GNSS antenna considerations........................................................................................................ 8
3.3 Updating firmware on C94-M8P........................................................................................................... 9
3.4 Configuration ....................................................................................................................................... 9
3.4.1 GNSS module configuration .......................................................................................................... 9
3.4.2 Base Station configuration........................................................................................................... 10
3.4.3 Rover configuration ..................................................................................................................... 13
4Operation....................................................................................................................14
4.1 Base in operation................................................................................................................................ 14
4.2 Rover in operation .............................................................................................................................. 14
4.2.1 Monitoring the quality of the RTCM stream ................................................................................ 15
5Evaluation interfaces .................................................................................................16
5.1 RS232/UART Interface ........................................................................................................................ 16
5.2 USB interface...................................................................................................................................... 16
5.3 J8 connector....................................................................................................................................... 16
5.4 Battery connector ............................................................................................................................... 17
5.5 LED..................................................................................................................................................... 17
5.6 Antenna connectors ........................................................................................................................... 17
5.6.1 Radio antenna connector ............................................................................................................ 17
5.6.2 GNSS antenna connector ............................................................................................................ 18
6Block diagram.............................................................................................................19
7Board layout ...............................................................................................................20

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8Schematic....................................................................................................................21
Appendix ..........................................................................................................................22
AGlossary ......................................................................................................................22
BRadio communication link configuration .................................................................22
B.1 Serial console terminal installation ...................................................................................................... 25
CNotes on FW3.01 HPG1.30 .........................................................................................26
DNotes on hardware ....................................................................................................26
D.1 Variants -00........................................................................................................................................ 26
D.1.1 Overview ..................................................................................................................................... 26
D.1.2 Connectors.................................................................................................................................. 26
D.1.3 Dimensions.................................................................................................................................. 27
Related documents...........................................................................................................28
Revision history................................................................................................................28
Contact..............................................................................................................................29

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1Introduction
1.1 Overview
The C94-M8P application board package provides the means for efficient integration and evaluation of
NEO-M8P, u-blox’s M8 high precision GNSS modules.
The NEO-M8P module series introduces the concept of a “Rover” and a “Base Station”. By using a data stream
from the Base Station, the Rover can output its relative position with stunning cm-level accuracy in good
environments.
The C94-M8P board integrates the NEO-M8P-2 module with both Base Station and Rover functionality. The
C94-M8P includes a UHF radio link, allowing for easy setup and fast prototyping. The board also provides
connector pins for u-blox C027 and other application boards, enabling communication alternatives using u-blox
cellular and short-range technologies.
The C94-M8P application board package comes in four variants, each with an individually configured radio link
to meet different radio frequency requirements in different regions:
C94-M8P-1-10 for China (433 MHz)
C94-M8P-2-10 for USA and Canada (915 MHz)
C94-M8P-3-10 or C94-M8P-3-10 for Europe (433 MHz)
C94-M8P-4-10 for Japan (920 Mhz)
A label showing the application variant (ordering code) is located at the top-right corner of the board. For
information about variants with the old board version (C94-M8P-1-00, C94-M8P-2-00 and C94-M8P-3-00) refer
to Appendix D.1.
1.2 C94-M8P package includes
The C94-M8P package includes:
2 application boards (both with a NEO-M8P-2 module)
2 external UHF antennas
2 external active GNSS antennas
2 antenna ground planes
2 USB cables
A RF-shield is attached on the top of the radio module.
A plastic enclosure is attached on the top of the GNSS module. The purpose of the enclosure is to prevent
airflow affecting TCXO performance.
1.3 Software requirements
For the instructions and examples in this document, we require the following software:
The latest version of u-center for Windows (currently version 8.24). You can download it from
https://www.u-blox.com/en/product/c94-m8p
Serial console terminal, for example Putty
1.4 System requirements
For the instructions and examples in this document, we have the following system requirements:
PC with USB interface
Operating system: Windows Vista onwards (x86 and x64 versions)
GNSS USB drivers are automatically installed when installing u-center.

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2Specification
Parameter
Specification
Interfaces
1 USB port for GNSS data and power supply
1 RS232, for radio link configuration
Connection pins for UART communication (e.g. C027), 3.3 V
SMA connector
External GNSS antenna and UHF antenna
Dimensions
75 mm x 55 mm
Weight
35 g
Power Supply
5 V via USB or externally powered by battery (5.05 mm pitch 2-pin, 3.7 V –20 V) powered
1 battery connector
Normal Operating temperature
-40°C to +65°C
Table 1: C94-M8P application board specification

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3Getting started
3.1 Software installation
The latest version of u-center (currently version 8.24) is needed for the examples and instructions described in
this document. Internet access is also required during the software installation to ensure that the most up-to-
date components are installed on your system. After installation, the u-center application can be found in the
”u-blox” folder in the Start->Program menu.
3.2 Hardware installation
To test and evaluate the benefits of u-blox’s Real Time Kinematic (RTK) technology, two C94-M8P application
boards –the “Base”and the “Rover”–need to be set up as described below.
Connect the UHF antenna to the SMA connector marked with “UHF”
Connect the GNSS antenna to the SMA connector marked with ”GNSS”
Connect the micro USB cable to the micro USB port on the board (for power and configuration)
Depending on the evaluation purposes, the test connectors may be used differently
The two boards are identical. Select one of the boards to
act as a “Base” and one as a “Rover”.
3.2.1 GNSS antenna considerations
In order to optimize the benefit of u-blox’s Real Time Kinematic (RTK) technology and achieve high accuracy
performance, the placements of the antennas are extremely important. The recommendations for the GNSS
antenna used with the system are:
The antenna needs to be placed in an open sky environment with unobstrucked visibility to the sky.
Care should be taken to minimize multipath. This can be achieved by using a ground plane, which is
supplied with the application board package for the GNSS antenna, and placing it above nearby buildings or
other obstructions.
If the installation does not provide a natural ground plane, such as a car roof, using a ground plane is
strongly recommended. The ground plane should have a minimum diameter of 10 cm. If better
performance is required due to multipath, then a larger ground plane will improve the performance.
Moving to a lower multipath environment might be required.
For more information, refer to Achieving Centimeter Level Performance with Low Cost Antennas [6].
Correct operation requires a static Base Station.

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3.3 Updating firmware on C94-M8P
Before starting evaluation, please check that the application boards are using the latest firmware. Information on
the latest firmware is published on the u-blox web site. For updating the firmware, follow the steps described in
chapter 7.1 Firmware Update u-blox 5-8 in u-center User Guide [4].
All the changes in configuration are lost when application boards are updated. Base and Rover must be re-
configured after updating
Do not have more than one application board connected to your computer while updating
3.4 Configuration
The C94-M8P package includes two identical boards featuring u-blox NEO-M8P-2 modules. You will configure
one of the boards to act as a Base Station, and the other will operate as a Rover.
3.4.1 GNSS module configuration
The NEO-M8P-2 positioning module on the C94-M8P application board is a concurrent GNSS receiver and can
receive and track multiple GNSS systems. The NEO-M8P module is configured by default for concurrent GPS and
GLONASS reception, where both constellations will be used in an RTK solution. Other available configurations
are GPS-only and GPS+BeiDou reception. A GPS-only setup can be used if higher RTK update rate is of interest.
The default GNSS constellation is GPS+GLONASS. For most users this is the optimal configuration and no
further configuration is needed.
If the configuration is changed –the changes need to be made for both boards as Base and Rover should
use the same GNSS systems.
For GNSS module configuration, use the micro-A USB port to connect with a PC running u-center. Once it is
connected, configure the module on u-center (View -> Message View -> UBX-CFG-GNSS) as shown in Figure 1.
For more information, refer to the u-center User Guide [4], the u-blox 8 / u-blox M8 Receiver Description
including Protocol Specification [1], and Protocol Specification Addendum for HPG1.30 [5].
Always remember to store configuration changes by sending the UBX-CFG-CFG message in u-center, which
can be done with the shortcut, .
Figure 1: Configuration of the NEO-M8P-2 GNSS module on C94-M8P application board

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3.4.2 Base Station configuration
The board that is selected to operate as Base needs to be configured as described below.
Setting up RTCM messages
A Base device needs to allow RTCM messages 1005 (Station coordinates), 1077 (GPS observations), 1087
(GLONASS observations) and 1230 (GLONASS code-phase biases) to go through the UART1 port on the receiver
module. UART1 refers to the connection between the NEO-M8P-2 GNSS module and the UHF radio module on
the application board. To do this, use the UBX-CFG-MSG messages as shown in Error! Reference source not
found..
RTCM messages should be configured to be output at 1 Hz. The output rate must be the same as the
Navigation Rate of Base station, which is 1 Hz by default.
RTCM messages do not need to be configured differently even if the Navigation Rate of the Rover is
configured differently, e.g. to have a higher output rate than the default 1 Hz.
Individual RTCM messages should be configured at the same rate.
The throughput of the RTCM communications link must be considered with respect to the amount of
bytes required for the enabled RTCM messages and message rates.
RTCM 1230 is required to make GLONASS ambiguity fixing possible.
If BeiDou is used, RTCM message 1127 needs to be used instead of 1087 (GLONASS), and RTCM 1230 can
be omitted.
MSM4 observation messages (i.e. 1074 for GPS, 1084 for GLONASS, and 1124 for BeiDou) can be used
instead of MSM7 to reduce the communication bandwidth requirements.
Figure 2: For a GPS+GLONASS setup, enable the RTCM messages 1005, 1077, 1087 and 1230 on UART1 port

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Base radio link
The radio link needs to be configured on the Base. Use the UBX-CFG-PRT message to set “Protocol in”to
“none”, as shown in Figure 3.
Figure 3: Configuring Base radio link
Base station operation
When the NEO-M8P functions as a Base Station, the receiver uses measurements from all available satellites to
broadcast corrections. By sending the UBX-CFG-TMODE3 message, the Base Station can be configured to
operate in a Fixed position mode or to self Survey-in its position, depending on the user’s knowledge of the Base
Station’s antenna reference position.
The Base Station must be configured with a Fixed position or have completed a Survey-in operation before it
will be able to output the RTCM reference station position message needed by the Rover.
The current firmware requires five ambiguities to attempt fixing. The RTK fixed status can therefore be
reached when either of the following requirements is fulfilled: 1) six satellites from a single constellation are
available, or 2) eight satellites from two different constellations are available.
Disable NMEA (disable child messages) in u-center to see TIME mode displayed in u-center.
Fixed position mode
In Fixed position mode, specify the Base Station’s antenna reference point with ECEF or Lat/Lon/Alt coordinates.
The corresponding fields are available via u-center, as shown in Figure 4. The coordinates can be specified with
0.1 mm resolution. For more information, see the Protocol Specification Addendum for HPG1.30 [5].
The accuracy of the specified coordinates will reflect directly in the absolute accuracy of the Rover’s position.
Figure 4: Configure to Fixed Position Mode for a Base Station

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Survey-in mode
If the coordinates of the Base Station antenna are not known with very good accuracy, the Base Station should
be configured to operate in Survey-in mode. When working in Survey-in mode the Base Station will determine its
own position by building a weighted mean of all valid 3D position solutions.
The UBX-CFG-TMODE3 message has two fields to fill in for survey-in mode, as shown in Figure 5. The first field,
“Minimum Observation Time”, defines a minimum amount of observation time regardless of the actual number
of valid fixes that were used for position calculation. Reasonable values range from one day for applications that
require high absolute accuracy, to a few minutes for applications that only require high relative accuracy.
The second field, “Required Position Accuracy”, forces the calculated Base station position to be of at least the
given 3D position accuracy.
Navigation Rate (UBX-CFB-RATE) should be 1 Hz during Survey-in.
Figure 5: Configure to Survey-in Mode for a Base Station
In operation, after both requirements are fulfilled, the Base station finishes the Survey-in mode and enters Fixed
mode automatically. Through the UBX-NAV-SVIN message, the Base operation status from Survey-in to Fixed can
be monitored, as shown in Figure 6.

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Figure 6: Base Station moving from Survey-in Mode to Fixed Mode
As the Base Station position error is inherited by the Rover absolute position error, users should carefully
evaluate the Rover absolute accuracy requirement and setup and choose the Base station mode accordingly.
3.4.3 Rover configuration
In its default mode, the Rover will automatically apply the RTCM corrections it receives. In effect, it will
immediately enter RTK float mode and, assuming circumstances allow for it, eventually reach RTK fixed mode.
In order to mitigate position jumps when switching between fixed and float modes, you can use RTK float-only
mode. Select it using the u-center message UBX-CFG-DGNSS. In this mode, the Rover will estimate the
ambiguities as float but will not attempt to fix them.
Rover radio link
Radio link needs to be configured on the Rover. Use UBX-CFG-PRT message to set Protocol out to “none”, as
shown in Figure 7.
Figure 7: Configuring Rover radio link

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4Operation
4.1 Base in operation
When the Base device is in normal operation, by enabling message UBX-NAV-STATUS, the Data View in u-center
shows “TIME” fix mode.
Figure 8: Data View shows “TIME” when Base is in FIXED mode
4.2 Rover in operation
When the Rover device is in normal operation, the Data View in u-center shows “FLOAT” or “FIXED” to indicate
the current operation mode.
Figure 9: Data View shows “FLOAT” or “FIXED” on Rover
Additionally, the message “UBX-NAV-RELPOSNED” in u-center shows more details about relative positions and
accuracies. For more information, refer to the u-center User Guide [4], the u-blox 8 / u-blox M8 Receiver
Description including Protocol Specification [1], and Protocol Specification Addendum for HPG1.30 [5].

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Figure 10: UBX-NAV-RELPOSNED in u-center for Rover
To achieve the expected accuracy of positioning with u-blox RTK technology, continued carrier phase
tracking is important.
4.2.1 Monitoring the quality of the RTCM stream
You can monitor the quality of the RTCM stream that the Rover receives. Use UBX-RXM-RTCM message to see
station ID, message type and CRC status.
Low latency (< 5 s) of the RTCM3 stream is critical for achieving a RTK FLOAT/FIXED solution at the Rover.
Any communication issues will prevent RTK FLOAT/FIXED being achieved.

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5Evaluation interfaces
The C94-M8P application board provides the specified interfaces as mentioned in section 2, for configuration,
logging, and measurement.
J1: RS232 –UART M8P/Radio
J2: USB –M8P
J3: External battery / DC connector
J6: Debugger interface for radio module
J8: Test & Production interface
J8: UART & GNSS features
oGeofence and RTK status
oInterface to e.g. u-blox C027
J10: Indicator LEDs
Figure 11: C94-M8P Application Board
5.1 RS232/UART Interface
There are two purposes for the UART interface on the board:
For configuring the radio module with AT commands
On the Rover board, to log the data stream (RTCM messages) sent from the radio module to the GNSS
module
Before configuring the radio module, the UART output of the GNSS module needs to be disabled.
See section Appendix B for radio communication link configuration.
5.2 USB interface
The C94-M8P board provides one micro-A USB interface, which is used for:
Configuring the GNSS NEO-M8P-2 module
Logging data sent out from the GNSS module, including UBX, NMEA messages.
5.3 J8 connector
The J8 connector is the combined interface for monitoring the Geofence status output and the RTK status
output, and is also a connector for the UART.
Geofence status corresponds to pin 15 and the RTK status corresponds to pin 16 on the NEO-M8P-2
module.
Pin 13, pin 14, pin 20 and any of the GND pins are for connecting to u-blox C027 and other application
boards. It enables communication alternatives using u-blox cellular and short-range technologies.
J8
J2
J1
J3
J6
J10

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The pin assignments of the 20-pin J8 connector are shown in Error! Reference source not found.. For more
information, see the NEO-M8P Data Sheet [2].
Pin Nr.
Assignment
1
V_BAT
2
GND
3
GND
4
RTK_STAT, monitor RTK status
5
GEOFENCE_STAT, monitor Geofence status
6
TIMEPULSE
7
GND
8
GND
9
RXD_GNSS
10
TXD_GNSS
11
GND
12
GND
13
RXD_EXT
14
TXD_EXT
15
GND
16
GND
17
SAFEBOOT_N
18
EXTINT
19
RESET_N
20
RADIO_OFF, apply 3.3 V to turn off the radio module for external UART communication.
Table 2: Pin assignments of J8 connector
5.4 Battery connector
There is a 2-pin battery connector available on the C94-M8P for connecting the board to an external battery or
DC supply. This uses a standard 5.05 mm pitch 2-pin connector for supplying a 3.7-20 VDC source or external
battery. The pin assignments of this 2-pin connector are shown in Error! Reference source not found..
Pin Nr.
Assignment
1
V_BAT, battery “+”
2
GND, battery “-”
Table 3: Pin assignments of battery connector
5.5 LED
The Blue LED (DS2), mounted on the C94-M8P application board, shows the time pulse output signal from the
NEO-M8P-2 module. The LED starts flashing one pulse per second during a GNSS fix. If there is no GNSS fix, the
LED will light up without flashing.
The Green LED (DS1) indicates the RTK status. The LED flashes in float mode and stays on in fix mode. The LED is
off when there is no RTK fix.
5.6 Antenna connectors
5.6.1 Radio antenna connector
The radio antenna SMA connector on each board is used for connecting a UHF antenna. This connector is
marked with the text “UHF” on the board.

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5.6.2 GNSS antenna connector
The GNSS module SMA connector on each board is used to connect the external active GNSS antenna. This
connector is marked with the text “GNSS” on the board.

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6Block diagram
Figure 12: Block diagram of the C94-M8P application board

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7Board layout
Figure 13: Board Layout of C94-M8P Application Board