Bluetooth 4.0: An introduction to Bluetooth Low Energy—Part II

URL : http://www.eetimes.com/document.asp?doc_id=1278966

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Figure 3: A simplified structure of a communication stack for various types of Bluetooth devices. The dual mode device introduced in Bluetooth 4.0 supports both Low Energy and legacy Bluetooth BR/EDR specifications. Single mode devices, typically budget and resource constrained, will support only the BLE specification. 

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Figure 4: Bluetooth LE stack for Single Mode devices. The lower part of the stack, a controller, handles time consuming functionality and it’s often combined together with a physical radio.  HCI provides a standardized interface between the Bluetooth LE controller and an arbitrary MCU which is hosting the application and the upper part of the stack.  If both parts of the stack are collocated on the same MCU, e.g. sensor SoC, HCI is not used.

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