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sparkfun RTK Express Hook-Up Manual

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SparkFun RTK Express Hookup Guide
Introduction
The RTK Express from SparkFun is your one stop shop for high precision geolocation and surveying needs. For
basic users, it's incredibly easy to get up and running and for advanced users, the RTK Express is a flexible and
powerful tool.
SparkFun RTK Express
 GPS-18442
With just a few minutes of setup, the RTK Express is one of the fastest ways to take centimeter grade
measurements.

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Summary of Contents for sparkfun RTK Express

  • Page 1 The RTK Express from SparkFun is your one stop shop for high precision geolocation and surveying needs. For basic users, it’s incredibly easy to get up and running and for advanced users, the RTK Express is a flexible and powerful tool.
  • Page 2 An RTK Fix with 14mm accuracy in SW Maps By connecting your phone to the RTK Express over Bluetooth, your phone can act as the radio link to provide correction data as well as receive the NMEA output from the device. It’s how $10,000 surveying devices have been operating for the past decade - we just made it easier, smaller, and a lot cheaper.
  • Page 3 Depending on your setup you may want to use your phone for RTCM correction data. If a source is not available online, you will need a 2nd RTK Express setup in base mode and a radio link connecting the Base to the Rover.
  • Page 4 GNSS RTK is an incredible feat of engineering that has been made easy to use by powerful GNSS receivers such as the ZED-F9P by u-blox (the receiver inside RTK Express). The process of setting up an RTK system will be...

  • Page 5: Hardware Overview

    At power on the device will enter Rover or Base mode; whichever state the device was in at the last power down. When the SETUP button is pressed the RTK Express will toggle between Rover and Base mode. The display will...
  • Page 6 In Base mode the device will enter Base Station mode. This is used when the device is mounted to a fixed position (like a tripod or roof). The RTK Express will initiate a survey. After 60 to 120 seconds the survey will complete and the RTK Express will begin transmitting RTCM correction data out the radio port.
  • Page 7 With the unit fully powered down, charging takes approximately 1.5 hours from a 1A wall supply or 3 hours from a standard USB port. The RTK Express can run while being charged but it increases the charge time. Using an external USB battery bank to run the device for extended periods or running the device on a permanent wall power source is supported.
  • Page 8 The connector is a 4-pin locking 1.25mm JST SMD connector (part#: SM04B-GHS-TB, mating connector part#: GHR-04V-S). The RTK Express comes with a cable to interface to this connector but additional cables can be purchased. You will most likely connect this port to one of our Serial Telemetry Radios if you don’t have access to a correction source on the internet.
  • Page 9 This 4-pin JST connector is used to output and input a variety of data to the RTK Express. The connector is a 4- pin locking 1.25mm JST SMD connector (part#: SM04B-GHS-TB, mating connector part#: GHR-04V-S). The RTK Express comes with a cable to interface to this connector but additional cables can be purchased.
  • Page 10 NMEA-GLL NMEA-GNS NMEA-GRS NMEA-GSA NMEA-GST NMEA-GSV NMEA-RMC NMEA-VLW NMEA-VTG NMEA-ZDA NAV-CLOCK NAV-DOP NAV-EOE NAV-GEOFENCE NAV-HPPOSECEF NAV-HPPOSLLH NAV-ODO NAV-ORB NAV-POSECEF NAV-POSLLH NAV-PVT NAV-RELPOSNED NAV-SAT NAV-SIG NAV-STATUS NAV-SVIN NAV-TIMEBDS NAV-TIMEGAL NAV-TIMEGLO NAV-TIMEGPS NAV-TIMELS NAV-TIMEUTC NAV-VELECEF NAV-VELNED RXM-MEASX RXM-RAWX RXM-RLM RXM-RTCM RXM-SFRBX MON-COMMS MON-HW2 MON-HW3 MON-HW...
  • Page 11 RTK Express. The RTK Express can be charged from any USB port or adapter. The charge circuit is rated for 1000mA so USB 2.0 ports will charge at 500mA and USB 3.0+ ports will charge at 1A.
  • Page 12 Hardware Overview - Advanced Features The RTK Express is a hacker’s delight. Under the hood of the RTK Express is an ESP32 WROOM connected to a ZED-F9P as well as some peripheral hardware (LiPo fuel gauge, microSD, etc). It is programmed in Arduino and can be tailored by the end user to fit their needs.
  • Page 13 LiPo and Charging The RTK Express houses a standard 1300mAh 3.7V LiPo. The charge circuit is set to 1A so with an appropriate power source, charging an empty battery should take a little over one hour. USB C on the RTK Express is configured for 2A draw so if the user attaches to a USB 3.0 port, the charge circuit should operate near the 1A...
  • Page 14 The lower Qwiic connector is exposed on the end of the unit. These allow connection to the I C bus on the ESP32. Currently the stock RTK Express does not support any additional Qwiic sensors or...
  • Page 15 A microSD socket is situated on the ESP32 SPI bus. Any microSD up to 32GB is supported. RTK Express supports RAWX and NMEA logging to the SD card. Max logging time can also be set (default is 10 hours) to avoid multi-gigabyte text files.

  • Page 16: Hardware Assembly

    Shown here is the most common RTK Rover setup. A monopole designed for cameras is used. A cell phone holder is clamped to the monopod and the RTK Express is mounted. The ¼” camera thread of the monopole is adapted to ⅝” 11-TPI and a L1/L2 antenna is attached. A Male TNC to Male SMA cable connects the antenna to the RTK Express.
  • Page 17 L1/L2 antenna with ground plate We strongly recommend against using a rigid helical antenna configuration as shown below. The RTK Express is not designed for such configurations and can lead to permanent damage to the antenna connector. The helical antenna becomes a large lever arm.
  • Page 18 Picture hanging strips from 3M make a nice semi-permanent mount. Plug the 4-pin to 6-pin JST cable included with the RTK Express from the Radio port to either of the Serial Telemetry Radios (shipped in pairs). We really love these radios because they are paired out of the box, either can send or receive (so it doesn't matter which radio is attached to base or rover) and they have remarkable range.
  • Page 19 Any tripod with a ¼” camera thread will work. The Amazon Basics tripod works well enough but is a bit light weight and rickety. A cell phone holder is clamped to the tripod and the RTK Express is held in the clamp. The ¼” camera thread is adapted to ⅝”...
  • Page 20 SW Maps with RTK Fix When powered on, the RTK Express will broadcast itself as either 'Express Rover-5556' or 'Express Base-5556' depending on which state it is in. Discover and pair with this device from your phone or tablet. Once paired, open SW Maps.
  • Page 21 From SW Map's main menu, select Bluetooth GNSS. This will display a list of available Bluetooth devices. Select the Rover or Base you just paired with. Select 'SparkFun RTK Surveyor' or 'u-blox RTK' (rather than just 'u-blox') from the Instrument Model dropdown. This is important and will enable the use of NTRIP. If your are taking height measurements (altitude) in addition to position (lat/long) be sure to enter the height of your antenna off the ground including any ARP offsets of your antenna (should be printed on the side).
  • Page 22 List of available Bluetooth devices Next we need to send RTCM correction data from the phone back to the RTK Express so that it can improve its fix accuracy. This is the amazing power of RTK Express and SW Maps. Your phone can be the radio link! From the main SW Maps menu select NTRIP Client.
  • Page 23 NTRIP Connection - Not there? Be sure to select 'u-blox RTK' instrument Enter your NTRIP caster credentials and click connect. You will see bytes begin to transfer from your phone to the RTK Express. Within a few seconds the RTK Express will go from ~300mm accuracy to 14mm. Pretty nifty, no?
  • Page 24 RTCM format. You, the user, don't need to know how to decode or deal with RTCM, you simply need to get RTCM from a source within 10km of your location into the RTK Express. The NTRIP client logs into the server (also known as the NTRIP caster) and grabs that data, every second, and sends it over Bluetooth to the RTK Express.
  • Page 25 The RTK Express has a 0.96" high-contrast OLED display. While small, it packs various situational data that can be helpful in the field. We will walk you through each display. Power On/Off RTK Express Startup and Shutdown Screens Press and hold the power button until the display illuminates to turn on the device. Similarly, press and hold the power button to turn off the device.
  • Page 26 The Fixed Base mode is similar but uses a structure icon to indicate a fixed base. Base Transmitting NTRIP RTK Express in Transmit Mode with NTRIP If the NTRIP server is enabled the device will first attempt to connect over WiFi. The WiFi icon will blink until a WiFi connection is obtained.

  • Page 27: System Configuration

    ⚡ Warning! All data in and out of RTK Express is 3.3V. Exposing these pins to 5V logic will damage the device.
  • Page 28 Rover-XXXX or Express Base-XXXX depending on which state it is in. The menus will timeout after 15 seconds of inactivity, so if you do not press a key the RTK Express will return to reporting status messages after 15 seconds.
  • Page 29 As of v1.13 of the ZED-F9P firmware there is a bug that, when SBAS is enabled, causes the RTK status pin to fail to work. SBAS does not improve or detract from the RTK Express precision. We recommend leaving SBAS disabled.
  • Page 30 Base The RTK Express can also serve as a correction source, also called a Base. The Base doesn't move and 'knows' where it is so it can calculate the discrepancies between the signals it is receiving and what it should be receiving.
  • Page 31 Settings for the NTRIP Server This is a new and powerful feature of the RTK Express. The RTK Express can be configured to transmit its RTCM directly over WiFi to the user's mountpoint. This eliminates the need for a radio link.
  • Page 32 By default the Radio port is set to 57600bps to match the Serial Telemetry Radios that are recommended to be used with the RTK Express (it is a plug and play solution). This can be set from 4800bps to 921600bps.
  • Page 33 UART1 becoming overwhelmed because the ZED cannot transmit at 115200bps fast enough. The Data port on the RTK Express is very flexible. It can be configured in four different ways: Internally the Data connector is connected to a digital mux allowing one of four software selectable setups. By default the Data port will be connected to the UART1 of the ZED-F9P and output any messages via serial.
  • Page 34 Option 2 allows a user to set the max logging time. This is convenient to determine the location of a fixed antenna or a receiver on a repeatable landmark. Set the RTK Express to log RAWX data for 10 hours, convert to RINEX, run through an observation processing station and you’ll get the corrected position with...
  • Page 35 Connect a USB A to C cable from your computer to the ESP32 port on the RTK Express. Now identify the com port the RTK Enumerated at. The easiest way to do this is to open the device manager: CH340 is on COM6 as shown in Device Manager If the COM port is not showing be sure the unit is turned On.
  • Page 36 -z --flash_mode dio --flash_freq 80m --flash_size detect 0 RTK_Surveyor_Firmware_v13_co mbined.bin Note: You will need to modify COM6 to match the serial port that RTK Express enumerates at. Programming via the esptool CLI Upon completion, your RTK Express will have the latest and greatest features! Creating Custom Firmware The RTK Express is an ESP32 and high-precision GNSS hackers’s delight.

  • Page 37: Troubleshooting

    SPARKFUN TECHNICAL ASSISTANCE PAGE If you don't find what you need there, the SparkFun Forums are a great place to find and ask for help. If this is your first visit, you'll need to create a Forum Account to search product forums and post questions.
  • Page 38 GPS-RTK2 Hookup Guide SparkFun GPS-RTK Dead Reckoning ZED-F9R Hookup Guide Get precision down to the diameter of a dime with the The u-blox ZED-F9R is a powerful GPS-RTK unit that new ZED-F9P from u-blox. uses a fusion of IMU, wheel ticks, a vehicle dynamics...