Currently, customers who are leveraging FreeRTOS-based devices and wish to connect to Azure need to resort to home-grown solutions or venture to adapt existing SDKs to get a working solution. With this middleware they'll get a proper SDK that exposes the APIs these developers expect to see when getting their devices connected to Azure. In contrast with home-grown solutions, the Azure IoT middleware for FreeRTOS is maintained and supported by Microsoft, and it is an open-source project that allows you to adapt it to a number of different hardware combinations to support your business and technical requirements.
Check out the samples for Azure IoT middleware for FreeRTOS on GitHub.