Explore the design and implementation of a secure, open-source DIN Rail Energy Monitor with a Linux host processor in this conference talk from linux.conf.au 2020. Dive into the evolution of IoT energy monitoring systems, from initial iterations using ESP8266 and ESP32 to the transition to a full-Linux capable host processor. Learn about the importance of security and privacy in IoT devices, and how open-source firmware allows users to audit these features. Discover the deep dive into Linux kernel module for SPI drivers, the use of ASIC's and FPGA's for real-time processing, and the potential of Python for energy monitor-specific code. Gain insights into components such as the SPI bus, OpenWRT, Arduino, MicroPython, MQTT, and various design inspirations for creating a privacy-focused energy monitoring solution.