RAKwireless has launched the WisMesh Pi HAT RAK6421, a HAT+ compliant expansion board that converts a Raspberry Pi into an always-on Meshtastic base station. Aimed at users running meshtasticd, the Linux-native Meshtastic service, the board is designed for fixed gateways, MQTT relays, and backbone nodes where ESP32-based handhelds run out of headroom for Node-RED, Grafana, and heavy MQTT traffic.
The interesting twist is that the RAK6421 ships without a soldered-on radio. Instead, it exposes two WisBlock IO slots and four sensor slots, so users pick their own LoRa module, swapping between the standard RAK13300 or the higher-output 1W RAK13302 depending on range and regulatory needs. The HAT speaks SPI, UART, I2C, and GPIO to those slots, adds four 16-bit analog inputs through an ADS1115-compatible SGM58031 ADC, and includes a CAT24C32-compatible EEPROM for HAT+ auto-discovery. Operating range is -40°C to +85°C (-40°F to 185°F), and downstream power rails deliver both 3.3V and a 4.17V VBAT to attached WisBlock modules.
Compatibility covers the Raspberry Pi 4, Raspberry Pi 5, and Raspberry Pi Zero 2W, plus other SBCs with a standard 40-pin header. The four WisBlock sensor slots accept existing modules including the RAK1906 (Bosch BME680 environmental sensor), RAK1901 (Sensirion SHTC3 temperature and humidity), RAK12019 UV sensor, and RAK12002 RTC, along with GNSS options like the Quectel L76K. Two extra headers expose AIN1, GPIO4, GPIO5, VBAT, and a separate I2C1 bus for custom add-ons.
On the software side, RAKwireless publishes a ready-to-flash Raspberry Pi image with meshtasticd preinstalled, documented in the quick start guide. Open-source scripts also automate the install of Mosquitto, InfluxDB, Node-RED, and a preconfigured Grafana dashboard, and the board is officially listed in Meshtastic's supported hardware. Users who prefer the manual route can drop meshtasticd onto stock Raspberry Pi OS, with wiring details in the datasheet.
The standalone HAT starts at $12.50 (€12) at the RAKwireless store, with bundled sensor kits running up to $96 (€88). Complete kits pairing the HAT with a Raspberry Pi 4 2GB or Raspberry Pi 5 4GB plus a preloaded microSD card are listed at $136 (€125) and $206 (€189). A RAK13300 or RAK13302 LoRa module is required separately if you don't already have one on the shelf. More details are on the product overview page.
