Reverse Engineering And Self-Hosting The OBI Smart Energy Tracker

Sold by German DIY store OBI, the OBI Energy Tracker is a €15 set of two devices, one of which you essentially stick on top of your existing electricity meter. This then allows for electricity usage to be measured and tracked, with the data sent to the second, gateway device. This latter cloud-bound device is linked to an OBI account via the heyOBI app. This correspondingly called for the gateway device to be reverse-engineered and freed from its cloud-based shackles, a task that [Aaron Christophel] happily took upon himself.

The whole process is also covered in two videos, with the first providing all the essentials on reprovisioning the original firmware for a local MQTT server in English, while the second, German-language video focuses on custom firmware for the ESP32-C3 inside of the gateway device.

Inside the reader device is a Cortex-M0+-based BAT32G135 MCU that communicates with the meter via its IR protocol. This is then communicated via 868 MHz LoRa to the gateway device that will be placed somewhere within Wi-Fi reach by the user. Inside this latter device is as mentioned the ESP32-C3, which by default runs firmware that communicates via secure MQTT with an AWS cloud instance for the typical cloud-based shenanigans.

The aforementioned reprovisioning option doesn’t require firmware flashing, just a handful of steps to follow. This involves fetching the 32-bit TEA key, generating your own PKI, running your own MQTTS-capable broker and having the provided Python script handle the rest from there.

Flashing custom firmware is the other option, with straightforward UART/JTAG reflashing sadly disabled by the manufacturer. With the effort required here you could perhaps argue that simply connecting the reader device to a custom gateway device might be a lot easier, especially if you already have a LoRa transceiver and associated hardware.