Such stack has to handle at least the device management: detect new device, enumerate, query device descriptors, etc… ST provides an USB Host stack as part of their STM32 Cube environment. While the STM32 F4 has an USB peripheral built-in, to actually use USB, an USB Host Stack is required. To keep the flexibility, we avoided using an RTOS – an RTOS could still be added if needed later. Starting with an existing port has the benefit that all but the Bluetooth transport has already been taken care of. For this port, we’ve selected the STM32 F4 Discovery board that we’ve used before.
However, such controller may become quite handy when we need to a) add Bluetooth functionality to existing devices with an USB port, and/or b) avoid radio emission testing for low volume products as the device is shipped without RF functionality.Īs there were request in the past for a BTstack USB port for MCUs and there have been a few implementations created by the BTstack community, we’ve decided to create such a port from scratch to learn about the challenges. Using a USB Bluetooth Controller has a higher complexity than one connected via the UART, mainly due to the need for an USB Host Stack. In this blog post, we provide an overview on how to use Bluetooth Controllers via USB as well report on our journey of porting BTstack to the STM32 F4 Discovery board which has an USB On-The-Go (OTG) interface.
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