SparkFun RTK Reference Station Hookup Guide

Contributors: PaulZC

Tried and Tested Configurations

The RTK Reference Station does so much that it is difficult for us to methodically test everything it is capable of.

We also need to be honest and say that the RTK firmware uses almost all of the RAM available on the ESP32-WROOM, especially on the Reference Station where we need to reserve additional RAM for the SDIO (SD_MMC) microSD interface and to buffer the high-bandwidth SPI data from the GNSS module. The Reference Station is slightly compromised as we do not have enough RAM to run WiFi, Bluetooth, SDIO and Ethernet at the same time, while pulling high message rate data from the GNSS.

The list below contains configurations that we have tried and tested, and have found to work well. But you will notice some missing configurations - like supporting TCP Client and Server over WiFi - for the reason outlined above.

• Base Mode: Survey-In or Fixed Position; NTRIP Server enabled - corrections are sent to the NTRIP Caster via Ethernet
  • Tested with rtk2go.com
  • A measurement rate of 1Hz is recommended (the default is 4Hz)
• Base Mode: Configuration via Bluetooth
  • Tested with Serial Bluetooth Terminal on Android
• Rover Mode: NTRIP Client enabled - corrections received from the NTRIP Caster via Ethernet
  • Tested with rtk2go.com
  • A measurement rate of 1Hz is recommended (the default is 4Hz)
• Rover Mode: NTRIP Client with location display on (e.g.) SW Maps
  • Tested using SW Maps on Android
  • SW Maps connected to rtk2go.com NTRIP Server / Caster via WiFi and providing corrections to the Reference Station via Bluetooth
  • Real-time display of Reference Station location and position accuracy via Bluetooth
• Rover Mode: Configuration via Bluetooth
  • Tested with Serial Bluetooth Terminal on Android
• NTP Mode
  • Tested with Raspberry Pi (with ntp and ntpq) and Windows PC (with Meinberg NTP - see the Product Manual for details)
  • Excellent agreement with NTP Pool servers
• Configure-Via-Ethernet Mode
  • Reference Station is booted into a dedicated mode to allow configuration via a web page over Ethernet
  • The Ethernet IP address is displayed on the OLED display
  • Supports microSD file upload / download and deletion
• Configure-Via-WiFi Mode
  • Identical to the other RTK products
  • Both Access Point (Hotspot) and network modes are supported
• TCP Client: provision of NMEA and / or UBX GNSS messages to an external TCP Server via Ethernet
  • Configured via the Ethernet Menu / configuration tab
  • NMEA and / or UBX messages can be sent to an external TCP server (to its IP address or URL)
• Firmware Update: update Over-The-Air via WiFi

Things Which Work - If You Are Careful

As we mentioned above, the Reference Station RTK firmware uses almost all of the ESP32-WROOM's RAM. Unfortunately this means you can not have both WiFi and Bluetooth running simultaneously for example. It also complicates things if you use additional RAM by: using the ESP-NOW radio link; or allocate extra RAM for high rate GNSS message storage.

The following configurations do work, but you do need to proceed carefully:

• ESP-NOW:
  • The E-Pair Mode does work, you can use the ESP-NOW radio link to send correction data from a Reference Station Base to a RTK Rover, but only if Bluetooth is disabled
  • Disable Bluetooth via the System Menu. Select "b" twice to: first select BLE mode; and then to disable Bluetooth completely
  • Restart the system using the System Menu \ Debug Menu: enter "s" followed by "d" followed by "r" to restart the Reference Station. This ensures the RAM used by Bluetooth is released
  • Select the E-Pair option by pressing the MODE button until "E-Pair" is displayed
  • Pair the Reference Station Base with an RTK Rover and the Rover will achieve RTK-Fix
  • Please see the Product Manual for more details
• RXM-RAWX and RXM-SFRBX Logging at 20Hz
  • The Reference Station can log RXM-RAWX and RXM-SFRBX at 20Hz, but only if you increase the size of the GNSS Handler Buffer
  • Start by disabling Bluetooth as described above
  • Open the System Menu \ Debug Menu and select option 35. Increase the GNSS Handler Buffer to 16384 - 65535 bytes for best results
  • Restart the Reference Station and then use the GNSS Receiver Menu to increase the measurement rate to 20Hz
  • For best results, use a freshly-formatted microSD card. The card write speed can reduce dramatically if it contains multiple files

Unsupported Configurations

The following is a summary of the configurations which the Reference Station does not currently support (as of firmware 3.4):

• Base Mode: Survey-In or Fixed Position; NTRIP Server enabled - corrections sent via WiFi
• Rover Mode: NTRIP Client enabled - corrections received via WiFi
• Firmware Update: update via Ethernet