Openviro Axe PoE is an RP2040-based environmental sensor for server rooms and cabinets (Crowdfunding)

Openviro Axe PoE is a rack-mountable, open-source environmental sensor designed to measure the temperature and humidity (and air pressure) in server rooms or cabinets with electrical equipment.

The device is based on a Raspberry Pi RP2040 board with Ethernet connectivity housed in a plastic enclosure and equipped with two RJ12 connectors for Bosch BME280 sensors with an accuracy of +/- 0.5°C. It provides better results than sensors placed in a machine that may be impacted by the internal components’ heat dissipation. For instance, the two sensor inputs can be used to measure the temperature and humidity of the intake and exhaust in a server rack.

Openviro Axe PoE specifications:

• Microcontroller – Raspberry Pi RP2040 dual Arm Cortex-M0+ @133 MHz with 264 KB SRAM
• Storage – 16 MB flash memory
• Network – 10/100Mbps Ethernet RJ45 port via LAN8710Ai
• Expansion – 2x RJ12 connector for THP Probes
• Misc – 3x Buttons
• Power Input (one or the other)
  • 5V via USB Type-C port
  • 24 – 54V Power over Ethernet (PoE – Active Class 1)
  • 12 – 48V DC via 5.5 mm barrel jack
• Dimensions – 90 x 82.8 x 28.8 mm
• Material – Aluminum enclosure

Openviro THP probes specifications

• RJ12 connector for interface with the Axe PoE
• Sensor
  • Bosch BME280 temperature/humidity/pressure sensor
  • Range
    • Temperarure: -40°C to +85°C; recommended: 0 to +60°C (PETG enclosure)
    • Humidity: 0 to 100% relative humidity
    • Air pressure: 300 to 1100 hPa
  • Accuracy: +/- 0.5°C; +/-3% relative humidity; +/- 1.7 hPa
• Dimensions – Not finalized, but the final product will be smaller than the prototypes shown below

The data is queried via the SNMP (Simple Network Management Protocol) protocol that’s been around for years and is still often used in monitoring systems. I even remember implementing software using it 25 years ago to manage VoIP CPEs. The RP2040 firmware currently supports SNMP v1 and v2c, and SNMP v3 support is currently in beta. There’s no need for internet/cloud access since everything works in the LAN.

It’s compatible with SNMP software such as Nagios, Observium, PRTG, CheckMK, Zabbix, and even Home Assistant. Craft Computing says it’s more accurate (0.5°C) and with a 0.01°C step, the charts are smoother than most other solutions, as shown in the comparison below.

The firmware will be open-sourced after the crowdfunding campaign and released on GitHub, but it looks like the hardware will be kept closed source.

Craft Computing launched the Openviro Axe PoE on Crowd Supply with a $45,000 funding target that’s almost been reached. The Openviro Axe PoE requires a $149 pledge with a THP probe, and additional probes cost $29 each. Shipping adds $8 to the US and $18 to the rest of the world, and backers should expect their rewards to ship by the end of September 2025.

It initially looked a bit pricey to me, but competing systems like Room Alert 3S ($299) or APC AP9641 ($188 + $69 = $257) cost even more. Note that the prices include one THP sensor probe.

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