Espism
This repo contins schematics and code to build a low cost ISM radio to wifi gateway.
Look at hardware/v2 for the hardware and verification for the software used to do hardware verification. The directory mqtt_sniffer contains an ISM to MQTT sniffer. Blog post is here.
Building
git clone --recursive https://github.com/SuperHouse/esp-open-rtos.git
vi esp-open-rtos/include/ssid_config.h # Fix wifi credentials
git clone https://github.com/kanflo/eor-spi.git esp-open-rtos/extras/spi
git clone https://github.com/kanflo/eor-rfm69 esp-open-rtos/extras/rfm69
export EOR_ROOT=$PWD/esp-open-rtos
cd mqtt_sniffer
make && make flash