mirror of https://github.com/ARMmbed/mbed-os.git
55 lines
2.3 KiB
Markdown
55 lines
2.3 KiB
Markdown
# HCI abstraction architecture
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The HCI driver is split into two interfaces:
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* `CordioHCIDriver`: It is the driver for a BLE controller. It contains
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the primitive necessary to start and initialize the controller.
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* `CordioHCITransport`: It is the transport interface which is used by the HCI
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driver to communicate with the controller.
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A `CordioHCITransport` is injected into a `CordioHCIDriver` at construction
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time. A `CordioHCIDriver` is also injected at construction time of a `BLECordio`
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instance.
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This can be summarized in the following diagram:
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## CordioHCITransportDriver
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The single responsibility of this driver is to handle the communication with
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the Bluetooth module. Basically, sending and reading bytes.
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Given that the Bluetooth specification defines standard transport interface, an
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implementation of the H4 interface is bundled in this port. It might be extended
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in the future with an implementation of the H5 interface. However, there is no
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plan to provide the SDIO implementation at the moment.
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This interface is defined in the header file
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[CordioHCITransportDriver.h](../driver/CordioHCITransportDriver.h)
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## CordioHCIDriver
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The responsibilities of this driver are:
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* Provide the memory which will used by the Bluetooth stack.
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* Initialize the Bluetooth controller.
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* Handle the reset/startup sequence of the Bluetooth controller.
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This interface is defined in the header file
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[CordioHCIDriver.h](../driver/CordioHCIDriver.h)
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A partial implementation is present in the file
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[CordioHCIDriver.cpp](../driver/CordioHCIDriver.cpp). It defines the function
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delivering memory to the stack and a complete reset sequence. However, it does
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not define any initialization for the Bluetooth controller, this part being
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specific to the controller used.
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The driver also provides an interface to perform RF testing on the BLE trasnmitter.
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This is done using the LE Receiver/Transmitter Test command and LE Test End command
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as described in the Bluetooth Core spec in Vol.2, Part E, 7.8.28-30.
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The driver allows to set preferred TX power. This is an optional feature
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(check return code) and the support for it and the extent of control is
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down to the BLE chip. Chips may have different allowed values, although the
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command will pick the closest value no smaller than requested. Please refer
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to the controller code or BLE chip documentation.
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