Designed and manufactured in Boulder, CO USA, the SparkFun RTK Postcard is a compact development board for your high-precision positioning and navigation needs. This board combines the Quectel LG290P GNSS RTK receiver with an Espressif ESP32-PICO-MINI-02 MCU module, running our latest RTK Everywhere firmware. The ESP32 provides the SparkFun Postcard with WiFi and Bluetooth® connectivity to operate as an NTRIP caster or client. Meanwhile, the 4-pin locking JST-GH connector allows users to transmit or receive RTCMv3 messages for RTK corrections from a local base station.

• The LG290P module is a quad-band, multi-constellation, high-precision, RTK GNSS receiver. The module can simultaneously receive signals from the L1, L2, L5, and L6/E6 frequency bands of the GPS, GLONASS, Galileo, BDS, QZSS, and NavIC GNSS constellations. In addition, the module supports SBAS augmentation systems (WASS, EGNOS, BDSBAS, MSAS, GAGAN, and SDCM), PPP services* (BDS PPP-B2b, QZSS CLAS, MADOCA-PPP, and Galileo HAS), RTCM, and RTK corrections for precision navigation with a fast convergence time and reliable performance. Connect with ease using a variety of interfaces, including UART, SPI*, and I²C*.

• The ESP32-PICO-MINI-02 is a powerful MCU module with WiFi, Bluetooth®, and BLE connectivity and comes integrated with 8MB SPI flash, 2MB SPI Pseudo static RAM (PSRAM), and a 40 MHz crystal oscillator. The ESP32 microcontroller itself features two CPU cores that can be individually controlled, with an adjustable clock frequency between 80 - 240MHz and a low-power co-processor for minor tasks, such as monitoring peripherals. It supports a range of peripherals including an SD card interface, capacitive touch sensors, ADC, DAC, Two-Wire Automotive Interface (TWAI), Ethernet, high-speed SPI, UART, I2S, I²C, etc.

In addition to the RTK Postcard, we created the Portability Shield for users' convenience. It’s important to note that the RTK Postcard is designed to have full functionality when combined with the Portability Shield! Simply connecting these products provides a 1.3” OLED display and a five-way button to navigate the configuration settings and display PNT data; a microSD card slot for data logging; and a LiPo battery charger with a fuel gauge to take the RTK Postcard "on the go. “All of these will operate plug-and-play without the need for new code.

With the pre-loaded RTK Everywhere firmware, users can seamlessly operate the RTK Postcard as a base station or rover. These modes also offer additional functions, based on the available wireless communication options:

• The RTK Postcard can transmit or receive RTCMv3 messages, locally, by using the built-in ESP-NOW radio (2.4GHz) or by connecting external SiK Telemetry radios.
• Through WiFi or Bluetooth®, the RTK Postcard can also function as an NTRIP caster or client.
• The RTK Postcard can transmit NMEA messages to a graphical information software (GIS) app on any mobile device, when paired as a Bluetooth® device.

SparkFun RTK Postcard Features

• Quectel LG290P quad-band, GNSS module
  • Concurrent signal reception: 5 + QZSS
    • L1, L2, L5, E6 frequency bands
  • GNSS Constellations:
    • GPS (USA)
    • GLONASS (Russia)
    • Galileo (EU)
    • BDS (China)
    • QZSS (Japan)
    • NavIC (India)
  • SBAS Systems:
    • WASS (USA)
    • SDCM (Russia)
    • EGNOS (EU)
    • BDSBAS (China)
    • MSAS (Japan)
    • GAGAN (India)
  • Built-in NIC anti-jamming unit
• ESP32-PICO-MINI-N8R2 module
  • Firmware: RTK Everywhere
  • Provides WiFi/BT connectivity
    • Wi­Fi 802.11b/g/n
    • Bluetooth
  • Buttons
    • EPS32 Reset
    • ESP32 Boot
• Breakout board:
  • Dimensions: 1.70" x 1.70" (43.2mm x 43.2mm)
  • Four mounting holes:
    • 4-40 screw compatible
  • Input Voltage Range: 3.0 to 5.5V (5V pin)
• Connections:
  • 19 PTH pins
  • 4-pin JST-SH Qwiic connector (x2)
  • USB-C connector
  • 4-pin locking JST-GH connector
  • SMA antenna connector
  • u.fl antenna connector
• LEDs:
  • STAT - Green general status indicator
  • PWR - Red 3.3V power indicator
  • PPS - Yellow Pulse-Per-Second indicator
  • RTK - White RTK fix/correction indicator
  • BT - Blue Bluetooth indicator
• Backup battery

LG290P General Features

• High-precision GNSS module
• Electrical Characteristics:
  • Supply Voltage: 3.15 to 3.45V
  • Current Consumption:
    • Normal Operation:
      • 91mA (300.3mW) (Acquisition)
      • 91mA (300.3mW) (Tracking)
    • Power Saving Mode:
      • 12μA (39.6mW) (Backup Mode)
• GNSS Frequency bands:
  • GPS: L1 C/A, L1C*, L5, L2C
  • GLONASS: L1, L2
  • Galileo: E1, E5a, E5b, E6
  • BDS: B1I, B1C, B2a, B2b, B2I, B3I
  • QZSS: L1 C/A, L1C*, L5, L2C
  • NavIC: L5
  • SBAS: L1 C/A
  • L-band PPP*:
    • PPP: B2b
    • QZSS: L6
    • Galileo HAS: E6
• Tracking Channels: 1040
• Horizontal Position Accuracy:
  • Autonomous: 0.7m
  • RTK: 0.8cm + 1ppm
• Vertical Accuracy:
  • Autonomous: 2.5m
  • RTK: 1.5cm + 1ppm
• Velocity Accuracy Without Aid: 0.03m/s
• Accuracy of 1PPS Signal: 5ns (RMS)
• RTK Convergence Time: 5s
• Time to First Fix (without AGNSS):
  • Cold Start: 28s
  • Warm Start: 28s
  • Hot Start: 1.7s
• Sensitivity:
  • Acquisition: -146dBm
  • Tracking: -160dBm
  • Reacquisition: -155dBm
• Dynamic Performance:
  • Maximum Altitude: 10000m
  • Maximum Velocity: 490m/s
  • Maximum Acceleration: 4g
• Update Rate:
  • Default: 10Hz
  • Max: 20Hz
• Antenna Interface:
  • External active antenna
  • Power Supply: External or Internal
• Interfaces
  • UART (x3)
    • Baud Rate: 9600–3000000bps
    • Default: 460800bps
    • Protocol: NMEA 0183/RTCM 3.x
  • SPI* (x1)
  • I2C* (x1)
• Operating temperature: -40 to 85°C
• Footprint: 12.2mm × 16mm × 2.6mm
• Weight: ~0.9g

ESP32 General Features

• Electrical Characteristics:
  • Operating Voltage: 3.0 to 3.6 V
  • Current Consumption:
    • RF Operation: 368mA (peak)
    • Normal Operation: 20-31mA
    • Light-Sleep: 0.8mA
    • Deep-Sleep: 5µA
• Xtensa® Dual-Core 32-bit LX6 Microprocessor (up to 240MHz)
  • 448KB of ROM and 520KB SRAM
  • 8MB SPI Flash
  • 2MB PSRAM
  • 16KB SRAM in RTC
• PCB antenna
• Wi­F 802.11b/g/n
  • Bit Rate: up to 150Mbps (802.11n)
  • Frequency Range: 2412 - 2484MHz
• Bluetooth
  • Bluetooth v4.2 Specification:
    • BR/EDR
    • Bluetooth LE
  • Transmitter Class: 1, 2, and 3
• Supported Peripherals:
  • SD card, UART, SPI, SDIO, I2C, LED PWM, Motor PWM, I2S, IR, pulse counter, GPIO, capacitive touch sensor, ADC, DAC, TWAI® (compatible with ISO 11898-1, i.e. CAN Specification 2.0), Ethernet MAC
• Operating Temperature: -40 to 85°C

• Design Files
  • Schematic
  • KiCad Files
  • Board Dimensions
  • STEP File
• Hookup Guide
  • User Manual - RTK Everywhere Firmware
  • CH342 USB Driver (manufacturer website)
    • Windows
    • MacOS
  • QGNSS Software (v2.0)
• Component Documentation
  • ESP32-Pico-Mini-02 Module Datasheet
    • ESP32-Pico SoC Series Datasheet
  • LG290P Product Brochure
  • RTK Application Note
  • GNSS Protocol Specification
  • Hardware Design
  • Firmware Upgrade Guide
  • CH342 Datasheet
  • RT9080 Datasheet
  • JST-GH Dimensions
• Qwiic Info Page
• GitHub Firmware Repo
• GitHub Hardware Repo