Second iteration of the Influencair sensor node, with numerous improvements over the NodeMCU version:

• swapped out NodeMCU, replacing ESP8266 with an Atmel SAMD21G18 ARM Cortex M0 as main MCU
• replaced SDS011 with a Honeywell HPM particle sensor, offering improved life time and reliability
• flexible power supply design with a SEPIC converter, allowing input voltages between 2 V and 20 V
• replaced USB connector with a much more reliable DC barrel jack
• replaced Wifi with LoRa 868 MHz, including planar PCB antenna

The evaluation version also includes NOx and VOC sensors, and circuitry to charge up a battery with solar panels.