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ESD Sensitivity

The mosaic-T module is sensitive to ESD. Use a proper grounding system to make sure that the working surface and the components are at the same electric potential.

ESD Precaution

As recommended by the manufacturer, we highly encourage users to take the necessary precautions to avoid damaging their module.

ESP32 Firmware

We have intentionally kept the ESP32 firmware as simple as possible - it only disciplines the TCXO oscillator and controls the OLED display. The SparkFun RTK Firmware or SparkFun RTK Everywhere firmware will not run on this product. The intention is that you can easily develop your own firmware for the GNSSDO(+) if the SparkFun firmware does not meet your needs.

The /Firmware/Binaries folder contains the firmware binaries.

You can update or reload the firmware using the SparkFun RTK Firmware Uploader.

You can of course modify the hardware too, should you want to. The design is completely open-source.

Hardware Overview

In this section, we walk you through the hardware design, interfaces, I/O connections, power options and more.

Power Options​

The mosaic-T and the ESP32 both required 3.3V power. To simplify the power circuitry, the four power sources are combined into a common 5V rail which then feeds individual 3.3V regulators for the mosaic-T and the ESP32.

Power connections

Power connections on the GNSSDO(+) PCB.

The GNSSDO can be powered individually or in combination, with any of the following:

  • USB Ports - 5V; delivered via the MOSAIC CONFIG and/or ESP32 CONFIG USB-C connectors.
  • Power-over-Ethernet - Range: 36 to 57V; delivered via the MOSAIC ETHERNET RJ45 MagJack connector.
  • External DC Power - Range: 9 to 36V; delivered via the VIN+ and VIN- screw cage terminals.

Powering the GNSSDO+ takes a little more thought and care. The double-oven oscillator in the GNSSDO+ draws more current than a standard USB (2.0) port can provide. You need to ensure that you use the provided 65W Power Delvery Wall Adapter if you are going to power the GNSSDO+ from USB. Also, the GNSSDO+ includes a Power Path priority circuit. From highest to lowest, the Power Path priorities are:

  • Power-over-Ethernet - Range: 36 to 57V; delivered via the MOSAIC ETHERNET RJ45 MagJack connector.
  • External DC Power - Range: 9 to 36V; delivered via the VIN+ and VIN- screw cage terminals.
  • CONFIG ESP32 USB Port - 5V from a Power Delivery Wall Adapter; delivered via the CONFIG ESP32 USB-C connector.
  • CONFIG MOSAIC USB Port - 5V from a Power Delivery Wall Adapter; delivered via the CONFIG MOSAIC USB-C connector.

If you have the CONFIG ESP32 USB Port connected to a standard USB (2.0) port, it will not be able to provide enough current. And due to the Power Path priority, it will not preferentially draw power from CONFIG MOSAIC USB Port. Your options are:

  • Provide power via Power-over-Ethernet or External DC Power since these have higher priority
  • Install a power switch in the CONFIG ESP32 USB Port cable to disconnect its power, forcing the GNSSDO+ to draw Power Delivery power from the CONFIG MOSAIC USB Port.

If you have CONFIG MOSAIC USB Port connected to a standard USB (2.0) port, ensure the Power Delivery Wall Adapter is connected to CONFIG ESP32 USB Port. The Power Path priority will ensure power is drawn from the CONFIG ESP32 USB Port.

Consult page 9 of the GNSSDO+ schematic for more details

Measure Current Draw

If you want to measure the board's current draw, you can open the MEAS jumper and measure the current via a pair of breakout pads (see the Jumpers section).

Protection Components

Diodes are used to combine and protect the power sources from each other. Also, a 2A resettable fuse (green) provides additional protection.

info

For more details, users can reference the GNSSDO schematic, GNSSDO+ schematic and the datasheets of the individual components on the board.

The mosaic-T and ESP32 both have USB-C connections. These USB ports can be used to power the GNSSDO during the initial configuration when the mosaic-T or ESP32 are connected to a computer. For GNSSDO+, ensure you are using the provided Power Path Wall Adapter as described above.

USB-C Connectors

USB-C connectors on the GNSSDO(+).

USB-C Power Connections

The USB-C device connections on the GNSSDO(+) PCB.

CH340 Driver

The CH340 allows the ESP32-WROVER to communicate with a computer/host device through the USB-C connection. This allows the ESP32 to show up as a device on the serial (or COM) port of the computer. Users will need to install the latest drivers for the computer to recognize the CH340 (see USB Driver section).

Septentrio logo mosaic-T​

The heart of our product is of course the mosaic-T GNSS module from Septentrio. It is a very sophisticated chip with multiple interfaces: UARTS, USB and Ethernet. On GNSSDO, the GPIO1 and GPIO2 pins are available as 0.1" test points should you need access to them. On GNSSDO+, GP1 and GP2 are available on the 10-way screw cage connector.

mosaic-T

The Septentrio mosaic-T GNSS module.

Espressif logo ESP32-WROVER​

The ESP32 processor is there to control (discipline) the 10 MHz TCXO oscillator and the OLED display. We have deliberately kept the ESP32 firmware as simple as possible. The intention is that you can write your own firmware using the Espressif IDF or Arduino IDE if you need to.

Espressif ESP32 on GNSSDO

The Espressif ESP32-WROVER processor on GNSSDO.

Espressif ESP32 on GNSSDO+

The Espressif ESP32-WROVER processor on GNSSDO+.

Think of the ESP32 as a co-processor, or riding shotgun... The mosaic-T COM1, COM3 and COM4 UARTs are linked to the ESP32, allowing the two to communicate directly without needing an Ethernet link. In our firmware, the PVTGeodetic and ReceiverTime messages are output on COM1. The ESP32 displays some of their content on the I2C OLED display, and then uses the content to discipline the TCXO oscillator. See Oscillator for more details.

ESP32 Firmware

We have intentionally kept the ESP32 firmware as simple as possible. The intention is that users can easily develop their, own firmware for the GNSSDO(+) using the Espressif ESP IDF or the Arduino IDE if the SparkFun firmware does not meet their needs.

The /Firmware/Binaries folder contains the firmware binaries.

You can update or reload the firmware using the SparkFun RTK Firmware Uploader.

The ESP32-WROVER-IE antenna is not connected. If you write your own firmware and want to use BT/WiFi connectivity, you will need to attach your own antenna to the u.FL connector on the ESP32 module.

Ethernet PHY Interface​

The mosaic-T has a KSZ8041NLI Ethernet PHY interface, connected using a Reduced Media-Independent Interface (RMII).

Ethernet Connector

Ethernet (PoE) conection.

Ethernet PHY

The Ethernet PHY on the GNSSDO(+) PCB.

No IP address?

Check the Ethernet interface is enabled. It may be disabled. Connect via the CONFIG MOSAIC USB-C port and open 192.168.3.1 on a web browser. Check the Communication \ Ethernet sub-page.

mosaic-T web page

mosaic-T web page (PNG) with Ethernet disabled.

mosaic-T web page

mosaic-T web page (PNG) with Ethernet enabled.

By default, the mosaic-T Ethernet port is configured for Dynamic Host Configuration Protocol (DHCP). It expects the router / Ethernet switch to provide it with an IP address. If the IP address is all zeros (0.0.0.0), check that your router has DHCP enabled. Most do.

If you need a static IP address, you can configure this through the mosaic-T's Communication \ Ethernet sub-page.

Subnet 3 is reserved for the mosaic-T's USB-C connection (Ethernet-over-USB). If your router / switch is allocating addresses using subnet 3 (192.168.3.***), please change its settings so it uses a different subnet.

USB-C Connectors​

The mosaic-T and ESP32 both have USB-C connections. The MOSAIC USB port is high-speed and connected to the T through a balancing transformer. The ESP32 USB port is connected through a CH340 USB-UART IC.

USB-C Connectors

USB-C connections: mosaic-T (left) and ESP32 (right).

USB-C Power Connections

The USB-C data connections on the GNSSDO(+) PCB.

info

The GNSSDO can draw power from either or both USB ports, in addition to Power-over-Ethernet and the DC-DC external input described above. Powering GNSSDO+ via USB takes a little more though and care. Please see the notes above.

CH340 Driver

The CH340 allows the ESP32-WROVER to communicate with a computer/host device through the USB-C connection. This allows the ESP32 to show up as a device on the serial (or COM) port of the computer. Users will need to install the latest drivers for the computer to recognize the CH340 (see USB Driver section).

µSD Socket​

The µSD socket is connected directly to the mosaic-T via a one-bit SDIO interface for fast data logging. The mosaic-T supports µSD cards with a FAT32 file system (i.e. only cards up to 32GB in size).

micro SD socket and log button

µSD slot and LOG button.

micro SD socket and log button

µSD socket and Log button on the GNSSDO(+) PCB.

Operation Instructions
Initial Configuration

Before logging can take place, it is necessary to define a "logging stream" using the Logging page or RxTools. Streams can contain NMEA or SBF (Septentrio Binary Format) data; SBF can contain RTCM and/or RINEX.

Logging stream configuration

µSD logging stream configuration.

Instructional Video

How to log data to the SD card of the Septentrio mosaic receiver module

Once the stream is defined, users can control the data logging operation through the LOG button.

  • A short press of the LOG button (<5s) toggles data logging to the SD card on and off.
    • The red LOG LED will flash while logging is taking place.
  • A long press, holding the LOG button for more than 5 seconds (>5s) and then releasing it, will force the board to:
    • Unmount the SD card if it was mounted
    • Mount the SD card if it was unmounted

SMA Connectors​

The GNSSDO has robust SMA connectors for the mosaic-T GNSS antenna, Pulse-Per-Second output, 10 MHz clock signal and the Event A input.

SMA Connections

The SMA connections on the SparkPNT GNSSDO.

Connector Polarity

All these SMA connectors have a standard polarity. When selecting antennas and/or cables for the GNSSDO, double-check the polarity for the connections and cables.

The Event A SMA connector is standard polarity. The voltage is adjustable via the VCCIO switch: 3.3V or 5V. 2.8V and 1.8V are also available via the jumper links (see the Jumpers section). The output can also be configured for 50 Ohm via the jumper links (see the Jumpers section).

EventA Connections

The SMA connector for the EventA input.

EventA Connections

The connection for the EventA input.

Input/Output Terminals​

The GNSSDO is equipped with a 10-way 3.5mm screw cage terminal connector.

IO Connections

I/O Screw Terminal Connections.

IO Connections

I/O Screw Terminal Connections on the GNSSDO PCB.

These terminals are described in the tabs below. For more information on the I/O terminals, you can refer to the GNSSDO schematic and the GNSSDO+ schematic.

The VIN+ and VIN- terminals allow the GNSSDO to be powered by an external DC power source - typically a 12V / 24V vehicle battery.

TerminalFunction
VIN+External voltage: Min: 9V; Max: 36V
VIN-Ground / Chassis / 0V
info

The DC-DC converter in the GNSSDO provides 1.5kV isolation between VIN+/VIN- and 5V/GND. There is no direct electrical connection between VIN- and GND.

Ground Loop

If desired, users can link VIN- to the adjacent GND screw cage terminal. However, this will bypass the voltage isolation and could introduce an unwanted ground loop, particularly if the GNSS antenna ground (shield, 0V) is also connected to the chassis.

Switches​

There are two miniature slide switches on the GNSSDO PCB:

Switches

GNSSDO Switches

But only one on the GNSSDO+ PCB:

Switches

GNSSDO+ Switches

warning

The mosaic-T module can either use its internal TCXO or accept an external signal as a frequency reference. However, the module will constantly reboot if the REF_I pin isn't provided a 10MHz sinusoidal signal and left floating. Therefore, users should only set the GNSSDO 10MHz switch to the IN position, only if a 10MHz clock signal can be provided; otherwise, the switch should remain in the OUT position.

Additionally, switching between an external and internal frequency reference must occur when the mosaic-T is powered off, or the module must be reset after switching states.

  • VCCIO: This switch sets the voltage of the Input Output Terminals (COM2 UART, Event B, SCL2 & SDA2 (GNSSDO), GP1 & GP2 (GNSSDO+))

    • The I/O voltage can be set to 3.3V (default) or 5V.

  • 10MHz: This switch changes the function of the 10MHz SMA connector

    tip

    This switch is only available on GNSSDO. The GNSSDO+ 10MHz SMA is output-only.

    • When set to OUT (default):
      • The SMA connector will output a 10MHz "CMOS" disciplined clock signal
      • The signal voltage is set by the VCCIO voltage selection switch
    • When set to IN:
      • The user must apply a clock signal from an external 10MHz oscillator; otherwise, the mosaic-T module will constantly reset
      • The input impedance is 50Ω
      • The detection level is -14dBm
      • The max supported input level is +12dBm

Status LEDs​

There are six status LEDs on the GNSSDO(+):

LEDs

The status indicator LEDs on the GNSSDO(+).

LEDs

The status indicator LEDs on the GNSSDO(+) PCB.

  • PWR - Power (Red)
    • Illuminates when power is applied
  • LOG - µSD Logging (Red)
    • Solid Red - µSD card is mounted
    • Blinking Red - Data is being logged
    • Off - µSD is dismounted or not present
  • LOCK - Oscillator Lock (Green)
    • The TCXO is locked to the correct frequency - as reported by PVTGeodetic RxClkBias
    • Connected to ESP32 GPIO pin 33
  • PVT - Position Velocity Time (Green)
    • Solid Green - The mosaic-T has valid Position, Velocity and Time
    • Off - Satellite signal not present or acquired
  • ERROR - GNSS Error (Yellow)
    • The GNSS Error status - as reported by PVTGeodetic Error
    • Connected to ESP32 GPIO pin 32
  • RTK - Real-Time Kinematic (Yellow)
    • This LED has little or no functionality on the GNSSDO(+) as the mosaic-T uses PPP, not RTK
    • Internally, it is connected to the mosaic-T GPLED2 pin
    • It can be configured for (e.g.) TRACKLED if desired

OLED Display​

The GNSSDO(+) has a 128x64 pixel OLED display, controlled by the ESP32 via I2C. After some initial diagnostic messages, the display will show position, time and other data from the mosaic-T PVTGeodetic, ReceiverTime and IPStatus SBF blocks.

OLED Display

The OLED display on the GNSSDO(+).

info

OLED display

Information on the OLED display.

  • Date & Time : YYYY/MM/DD HH:MM:SS from ReceiverTime
  • IP : nnn.nnn.nnn.nnn from IPStatus IPAddress
  • Lat : Latitude from PVTGeodetic (Degrees)
  • Long : Longitude from PVTGeodetic (Degrees)
  • Sys : TimeSystem from PVTGeodetic
    • GPS, Galileo, GLONASS, BeiDou, QZSS, Fugro
  • Error : Error from PVTGeodetic
    • None, Measurements, Ephemerides, DOP, Residuals, Convergence, Outliers, Export, Differential, Base, Ambiguities
  • Fine : FINETIME from ReceiverTime
    • False, True
  • PPS : Indicates if the Pulse-Per-Second signal is being generated
    • Off, On
    • PPS is only generated once the RxClkBias has achieved the required accuracy
  • Bias : RxClkBias from PVTGeodetic (ms/us/ns)

The display is updated on arrival of the ReceiverTime message. You may see a small lag between the display and the actual time system time, but it will be minimal.

Buttons​

There are three buttons on the GNSSDO(+): RESET, BOOT, and LOG.

Buttons

Buttons on the GNSSDO(+).

Buttons

Buttons on the GNSSDO(+) PCB.

  • Septentrio logo mosaic-T: Data Logging

    • Once a logging stream is defined, users can control the data logging operation through the LOG button.

      • A short press of the LOG button (<5s) toggles data logging to the SD card on and off.
        • The red LOG LED will flash while logging is taking place.
      • Holding the LOG button for more than 5 seconds (>5s) and then releasing it, will force the board to:
        • Unmount the SD card if it was mounted
        • Mount the SD card if it was unmounted
      • The SD card must be mounted to allow data logging by the mosaic-T
      • When the SD card is unmounted, it is accessible as a mass storage device via the CONFIG MOSAIC USB-C interface
        • Files can be read and written over USB while the SD card is unmounted
      • You can enter commands using the Admin \ Expert Console to:
        • Change what happens when the disk is full
        • Change how the files are named
        • Change the mounting / unmounting of the disk
      • Consult section 3.2.20 of the Firmware Reference Guide for more details
      Instructional Video

      How to log data to the SD card of the Septentrio mosaic receiver module

  • Espressif logo ESP32: Reset

    • The RESET button allows users to reset the firmware running on the ESP32-WROVER module without disconnecting the power.

  • Espressif logo ESP32: Boot Control

    • The BOOT button can be used to force the ESP32 into the serial bootloader. Holding down the BOOT button, while connecting the GNSSDO(+) to a computer through its USB-C connector or resetting the board will cause it to enter the Firmware Download mode. The ESP32 will remain in this mode until it power cycles (happens automatically after uploading new firmware) or the RESET button is pressed.
      1. Hold the BOOT button down.
      2. Reset the MCU.
        • While unpowered, connect the board to a computer through the USB-C connection.
        • While powered, press the RESET button.
      3. Release the BOOT button.
      4. After programming is completed, reboot the MCU.
        • Press the RESET button.
        • Power cycle the board.

Jumpers (GNSSDO)​

Never modified a jumper before?

Check out our Jumper Pads and PCB Traces tutorial for a quick introduction!

There are several jumpers on the GNSSDO PCB which can be used to (e.g.) disable the LEDs or allow measurement of the board's current draw.

Jumpers

The jumpers on the top of the GNSSDO PCB.

  • POE - This jumper can be used to disconnect the Power-over-Ethernet (PoE) module 50Ω load.
    • The PoE module has a minimum load of 200mA. We included the 50Ω load to ensure this is met. If you can ensure this by other means, open this jumper to disconnect the load.
  • Voltage Configuration: A-V
    • The jumper links A-V can be used to configure the voltage levels and impedance of the SMA connections. Please refer to the schematic for additional information.
    • To configure the 10MHz output for 50 Ohms: open jumper A and close jumper D.
      • Jumper A is closed by default. Open it to select 50 Ohms for the 10MHz output.
      • Jumper B is closed by default. It could be used to isolate the gate driving the 10MHz output. Advanced use only.
      • Jumper C is open by default. It could be used to select the alternate gate for the 10MHz CMOS output. Advanced use only.
      • Jumper D is open by default. Close it to select 50 Ohms for the 10MHz output.
    • To configure the PPS output for 50 Ohms: open jumper E and close jumper H.
      • Jumper E is closed by default. Open it to select 50 Ohms for the PPS output.
      • Jumper F is closed by default. It could be used to isolate the gate driving the PPS output. Advanced use only.
      • Jumper G is open by default. It could be used to select the alternate gate for the PPS CMOS output. Advanced use only.
      • Jumper H is open by default. Close it to select 50 Ohms for the PPS output.
    • Jumpers J,K,L configure the voltage of the Event A input.
      • Jumper J is closed by default. It selects VCCIO as the Event A input voltage.
      • Jumper K is open by default. Open jumper J and close jumper K to configure Event A for 2.8V.
      • Jumper L is open by default. Open jumper J and close jumper L to configure Event A for 1.8V.
    • Jumpers M,N,P configure the voltage of the PPS output.
      • Jumper M is closed by default. It selects VCCIO as the PPS output voltage.
      • Jumper N is open by default. Open jumper M and close jumper N to configure PPS for 2.8V.
      • Jumper P is open by default. Open jumper M and close jumper P to configure PPS for 1.8V.
    • Jumpers R,S,T configure the voltage of the 10MHz output.
      • Jumper R is closed by default. It selects VCCIO as the 10MHz output voltage.
      • Jumper S is open by default. Open jumper R and close jumper S to configure 10MHz for 2.8V output.
      • Jumper T is open by default. Open jumper R and close jumper T to configure 10MHz for 1.8V output.
    • Jumper U can be used to isolate the on-board 10MHz TCXO.
      • Open jumper U when connecting an alternate TCXO via the breakout pads on the PCB. Advanced use only.
    • To configure the Event A input for 50 Ohms: close jumper V.
      • Jumper V is open by default. Close it to select 50 Ohms for the Event A input.

Jumpers (GNSSDO+)​

Never modified a jumper before?

Check out our Jumper Pads and PCB Traces tutorial for a quick introduction!

There are several jumpers on the GNSSDO+ PCB which can be used to (e.g.) disable the LEDs or allow measurement of the board's current draw.

Jumpers

The jumpers on the top of the GNSSDO+ PCB.

  • Voltage Configuration: A-D
    • The jumper links can be used to configure the voltage levels and impedance of the SMA connections. Please refer to the schematic for additional information.
    • Jumpers A,B,C configure the voltage of the Event A input.
      • Jumper A is closed by default. It selects VCCIO as the Event A input voltage.
      • Jumper B is open by default. Open jumper A and close jumper B to configure Event A for 2.8V.
      • Jumper C is open by default. Open jumper A and close jumper C to configure Event A for 1.8V.
    • To configure the Event A input for 50 Ohms: close jumper D.
      • Jumper D is open by default. Close it to select 50 Ohms for the Event A input.