Blog – TOPCON tractor + Drone – ESPRTK ESP32 F9P Radio Base Station RTK – Kenji Yamashita

TOPCON tractor + Drone – ESPRTK ESP32 F9P Radio Base Station RTK – Kenji Yamashita

Kenji Yamashita (山下健司) is from Japan.

He is a technology farmer, an engineer and a father of the family!

He sent us a request for help trying to build an RTK Base station for his TOPCON AGI-4 tractor and Drone (irrigation agriculture) .

Before he is used NTRIP service with internet connection.

However, it is expensive and complicated (combining phone, bluetooth and port switch…).

The problem is that he doesn’t want to depend on internet connection and wants to use only Radio UHF 433Mhz – 998Mhz connection.

He tried to use the EMLID receiver with no success.

We then helped him set up a low cost RTK station to use for TOPCON AGI-4 .

On the Base side, the RTK receiver is the Ublox F9P which acts as a Base and outputs messages RTCM 1005,1077 and 1087.

Using ESPrtk (ESP32) as a data forwarder, convert RTCM 1077,1087 to RTCM 1004,1012 and inject messages 1008,1033, 1006.

Finally there is a stream of RTCM 1004,1012,1005,1008,1006,1033 on the TX-UART2 port of the ESPrtk.

These messages will be sent to TOPCON via a UHF radio transmitter.

Of course, since the Serial input on TOPCON AGI-4 is RS232, we need to use a UART-RS232 converter module!

The result is he got RTK FIX on the first try. Congratulations !

He uses ESPrtk 3.9.99 Pro.

Run in “UART_Base_to_UART_Rover” mode.

Below are the video and photos he sent us of his project.

All images and videos copyright belongs to Kenji Yamashita – .

He is intending to sell his ready-made receivers to anyone and anywhere in the world.

If you want to buy , you can contact him.

See contact information at the bottom of this website.

If you want to build your own RTK Base station, read more here (Full instructions, connection diagram, how to configure):
NTRIP RTK Basestation – PX1122R / F9P + ESP32 + TRIMBLE, TOPCON, John Deere – ESP32 RTK.
Link :


  • App Build : NTRIP/MQTT RTK BaseStation+Rover
  • ESP32 : ESP32 DEV KIT C Espressif (ESP32_WROOM_32U or ESP32_WROOM_32UE CHIP
  • RTK GNSS: F9P or PX1122R
  • Ethernet : W5500 ( option !)
  • Display: OLED SSD1306 0.96 inch or SH1106 1.3 inch ( option !)
  • Power supply: 5V 2.5A Adapter
  • Other: LED , Button, Switch , 2.4Ghz WiFi Antenna , GNSS RTK Antenna, RJ45 Etheret cable, Micro USB Cable , 3.3V Active Buzzer , …

Hardware connection – ETHERNET + Full standards.

For RTK Basestation applications with up to several months or years of continuous uptime, we always recommend users to use the W5500 Ethernet module for their systems to ensure a stable 24-hour connection !.

In addition, it is possible to add 1 buzzer on the ERROR LED pin (3.3V Active Buzzer) and 1 small OLED module to be able to see the operating status, (connection status, error, flow rate, etc.) of the whole. system .

To connect ESPrtk with RTK receiver, Ethernet, OLED …,  Click here for more detail.  

Warning !

For those who are intending to use buzzer on ESPrtk.

To protect ESP32 chip. Do not connect the buzzer directly to the ESP32’s GPIO12 pin.

Please use protection diode (or combine with NPN transistor as shown image below).

Other Kenji Yamashita’s projects with his team.

Below are some images of the Drone RTK Radio Base project and some other projects (not this ESPrtk Base project).

These are collected on Facebook posts by Kenji Yamashita along with his team.

All images and videos copyright belongs to Kenji Yamashita – .

Contact – Kenji Yamashita (山下健司)

All images and videos copyright belongs to Kenji Yamashita – .

ESPrtk Q/A support team :

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