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CC254X WITH EXT MCU
This page describes some common configurations when using a CC254x in combination with an external MCU.
|Network Processor GATT_DB_OFF_CHIP||
|Network Processor Custom||
|Stand Alone App with Serial Interface||
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:
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
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
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
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
See the following wiki page for all 4 UART configuations: http://processors.wiki.ti.com/index.php/All_4_uart_configs