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CC254X WITH EXT MCU

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This page describes some common configurations when using a CC254x in combination with an external MCU.

Overview[edit]

Name Description Advantages Disadvantages
Network Processor
  • External MCU drives application using CC254x HCI API.
  • GATT database is stored on chip.
  • Prebuilt image available
  • No IAR programming required
  • Standard API
  • No custom profile support
Network Processor GATT_DB_OFF_CHIP
  • External MCU drives application using CC254x HCI API.
  • GATT database is stored off chip.
  • Based off standard HostTestRelease project
  • Custom profile allowed
  • Standard API
  • Must compile with GATT_DB_OFF_CHIP config
  • EXT MCU must handle all data read and writes
Network Processor Custom
  • HostTestRelease project modified to add custom profile and commands
  • Based off standard HostTestRelease project
  • Custom profile support
  • Standard API supported
  • Custom command support
  • Must modify code on CC254X to add profiles
  • Must modify code on CC254X to add commands
Stand Alone App with Serial Interface
  • Full stack, app and profiles with serial interface.
  • Data can be passed between MCU and CC254X over user defined API.
  • Can be optimized for minimal serial traffic
  • Logic can be divided between EXT MCU and CC2540
  • Easily leverage existing examples and certified profiles
  • Must define and implement serial API


Network Processor[edit]

The HostTestRelease project (included with standard BLE SDK) is the standard BLE Network Processor application. It can be loaded on the CC2540 or CC2541, with the any of the following used as a network processor interface:

1. UART
2. SPI
3. USB CDC virtual UART (CC2540 only)

More information on the HostTestRelease project can be found in the CC254x BLE Software Developer's Guide (http://www.ti.com/lit/pdf/swru271). An overview of the HCI command protocol can be found in the TI BLE Vendor Specific HCI Guide, which is linked from the Windows Start Menu after you have installed the SDK.

For applications which only act as a GATT client and do not need to act as a GATT server, this is an ideal choice.

Network Processor GATT_DB_OFF_CHIP[edit]

The HostTestRelease project has an option that can be enabled by including the preprocessor define "GATT_DB_OFF_CHIP" to the project configuration (under compiler settings). By adding this define, the network processor will be built such that any GATT services are maintained by the external MCU. This includes handling of all peer GATT requests to read, write, and discover services and characteristics.

This option provides for maximum flexibility of the GATT server by the MCU; however the code required on the external MCU is fairly complex.

More information on this type of setup can be found here: http://processors.wiki.ti.com/index.php/LPRF_BLE_NPGATT

Network Processor Custom[edit]

Rather than using GATT_DB_OFF_CHIP, another possibility is to manually add your GATT profiles to the HostTestRelease project, and rebuild the project with the services integrated into the network processor. This reduces the complexity of the external MCU code; however it requires the ability to add custom commands to the network processor in order to allow the external MCU to manage the data in the GATT services.

More information on this type of setup can be found here: http://processors.wiki.ti.com/index.php/BLE_HostTest_Add_Cmds

Stand Alone App with Serial Interface[edit]

Instead of using the HostTestRelease network processor project, another option is to take one of the existing single-chip projects included in the BLE SDK (e.g SimpleBLEPeripheral, HeartRate, RunningSensor, etc...) and modify it to include a "UART bridge" or a "SPI bridge", giving the external MCU the ability to communicate with the CC254x.

In addition to creating the brige using the HAL UART or HAL SPI drivers, a communication protocol must be established, allowing the external MCU to send commands to the CC254x (e.g. start advertising, send notification, etc...). It also must allow the CC254x to send event to the external MCU when specific actions occur (e.g. connection established, connection terminated, etc...). For many applications this protocol can be very simple and just consist of a few key commands and events.

More information on this type of setup can be found here: http://processors.wiki.ti.com/index.php/SimpleBLEPeripheral_SerialInterface

Other UART Configurations[edit]


See the following wiki page for all 4 UART configuations: http://processors.wiki.ti.com/index.php/All_4_uart_configs

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