Video on Hacking 433 MHz Devices with an RTL-SDR and Raspberry Pi
Over on YouTube user Andreas Spiess has uploaded a video showing how to use an RTL-SDR to reverse engineer 433 MHz ISM band devices such as Internet of Things (IoT)/home automation sensors and actuators.
Andreas decided to do this because he has a 433 MHz remote controlled actuated outdoor awning which he wants to have automatically retract when the wind speed gets too high. To do this he wanted to use a wireless 433 MHz ISM band weather station with wind speed sensor. But unfortunately he discovered that it has a proprietary protocol that can't talk to his awning, which also has it's own proprietary protocol.
Andreas' solution is to use an RTL-SDR and Raspberry Pi running the rtl_433 decoder software to receive the weather station data. The rtl_433 software already contained a decoder for his weather station, so no further reverse engineering was required. The data is then converted into MQTT which is a common TCP/IP protocol for IoT devices. MQTT is then read by Node-RED which is a flowgraph based programming environment for IoT devices.
Next, unlike the weather station rtl_433 did not already have a decoder implemented for his awning. So Andreas had to reverse engineer the signal from scratch using the Universal Radio Hacker software. Using the reverse engineered signal information, Andreas then uses an ESP32 processor/WiFi chip and cheap 433 MHz transmitter to implement a clone of the awning's remote control signals. The ESP32 is programmed to understand the MQTT data sent from the Raspberry Pi via WiFi, so now the weather station can control the awning with a little bit of logic code in Node-RED.