RAKwireless WisMesh Pi HAT RAK6421 is a modular Meshtastic gateway expansion board for Raspberry Pi 4/5 that adds support for the company’s WisBlock ecosystem. Designed for users running meshtasticd (the Linux-native Meshtastic service), it enables scalable, always-on Meshtastic base stations, MQTT gateways, and backbone relay nodes.
Unlike other LoRa solutions based on Raspberry Pi, the RAK6421 takes a modular approach. Instead of a built-in radio, it offers two WisBlock IO slots and four sensor slots, allowing users to easily plug in or swap modules. This means you can choose between standard LoRa modules like the RAK13300 or higher-power 1W versions like the RAK13302, without dealing with messy USB adapters or breadboard wiring.
RAK6421 WisMesh Pi HAT RAK6421 specifications:
- Compatibility
- Raspberry Pi 4, Raspberry Pi 5, and Raspberry Pi Zero 2W SBCs
- Potentially other SBC with standard 40-pin Raspberry Pi GPIO header (HAT+ compliant)
- Expansion
- 2x WisBlock IO slots for LoRa radio modules and other IO modules
- SPI, UART, I2C, and GPIO signals
- 4x analog inputs (0…3.3V) via SGM58031XMS10G/TR (ADS1115 compatible) 16-bit, low-power, precision sigma-delta (ΔΣ) analog-to-digital converter
- 4x WisBlock Sensor slots (Slot A, B, C, D) for I2C modules like GNSS (Quectel L76K), environmental sensors (BME680, SHTC3), and RTCs
- 4-pin J8 header exposing AIN1, GPIO4, GPIO5, and VBAT
- 4-pin J9 header exposing 3.3V, GND, I2C1_SCL, and I2C1_SDA
- 2x WisBlock IO slots for LoRa radio modules and other IO modules
- Misc – Onboard CAT24C32-compatible EEPROM connected to ID_SD/ID_SC for hardware auto-discovery; read-only by default (read-write mode accessible by shorting J10 pins)
- Power Supply
- 5V input (4.9V to 5.1V) from the Raspberry Pi 40-pin header
- Downstream power delivery of 3.3V and 4.17V (VBAT) to connected WisBlock modules
- Dimensions – Standard Raspberry Pi HAT form factor
- Temperature Range – -40°C to +85°C (operating)
ESP32-based nodes like the LR2021 LoRa Plus, the T-Display S3 Pro LR1121, the LILYGO T-LoRa Pager, and other similar nodes work well as portable, battery-powered devices. However, fixed gateways that need to handle heavy MQTT traffic, Node-RED, or Grafana dashboards quickly hit performance limits on a microcontroller. The WisMesh Pi HAT RAK6421 solves this by letting you run Meshtastic on a Raspberry Pi. It provides stable SPI, I²C, and UART connections, making it much more reliable for long-term telemetry and gateway use.
On the software side, RAKwireless provides a ready-to-use Raspberry Pi image with meshtasticd already installed and configured, which can be downloaded from their quick start guide. They also offer open-source scripts that automatically install Mosquitto MQTT, InfluxDB, Node-RED, and a pre-configured Grafana dashboard. You can check the product overview page for more details. You can also manually install Meshtastic on standard Raspberry Pi OS or build a custom image. More information on that can be found in the datasheet. The RAK6421 is also officially supported by Meshtastic.
The HAT natively supports a wide array of existing WisBlock modules, including the RAK1906 (Bosch BME680 environment sensor), RAK1901 (Sensirion SHTC3 temp/humidity), RAK12019 (UV sensor), and RAK12002 (RTC module).
The WisMesh Pi RAK6421 HAT is available on AliExpress starting at $12.50 for the standalone board, with bundled options (including sensors like RS485, environmental, and CO₂ modules) priced up to $95.90. Alternatively, you can also find bundles with a Raspberry Pi 4 2GB or Raspberry Pi 5 4GB and a microSD card preloaded with the software for $135.99 and $205.99, respectively. Finally, you’ll also find all these on the RAKwireless store. You’ll also need to add a RAK13300 or RAK13302 (1W) LoRa module if you don’t already own one.
Debashis Das is a technical content writer and embedded engineer with over five years of experience in the industry. With expertise in Embedded C, PCB Design, and SEO optimization, he effectively blends difficult technical topics with clear communication
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