A new development kit from Memec Design lets you implement Bluetooth wireless technology on Spartan-IIE FPGAs with MicroBlaze soft processors.

After several false starts, Bluetooth™ short-haul wireless connectivity technology for embedded systems finally seems ready for prime time. Bluetooth technology is just now beginning to gain momentum, and we expect it to grow significantly in the coming years.

For that reason, Insight Memec and Memec Design have developed an Embedded Bluetooth Development Kit featuring a Xilinx Spartan™-IIE FPGA coupled with a Xilinx MicroBlaze™ soft-processor core.

Bluetooth Basics
Bluetooth technology is a frequency hopping spread spectrum (FHSS) system that operates in radio frequencies in the 2.4 GHz to 2.5 GHz ISM band, and it has a maximum data throughput of 723.2 Kbps.

As with most standards, interoperability is key to success. The Bluetooth Special Interest Group’s goals include maintaining an open specification, delivering voice and data capability, and providing worldwide usability for short-range wireless solutions. The specification defines the protocols and profiles used by Bluetooth-certified products. Usage models define the real-world applications, and these usage models result in profiles as defined in the Bluetooth specification.

Profiles are basically instructions for implementing usage models. The profiles assure interoperability by providing a well-defined set of higher layer procedures and uniform ways of using the lower layers of the Bluetooth protocol. The serial port profile (SPP), for example, provides basic RS-232 serial cable emulation for Bluetooth devices. Legacy applications do not have to be modified to use Bluetooth technology; they can simply treat a Bluetooth link as a serial cable connection.

Adding Bluetooth capability requires the key elements shown in Figure 1. The RF radio and the baseband processor are typically available as an integrated Bluetooth transceiver solution.

The transceiver chip provides a serial interface to the host processor via USB or UART ports. The host processor typically executes the upper protocol-specific functions defined by the Bluetooth standard.

These protocol functions are known as the Bluetooth protocol stack and can be licensed in processor-specific binary or independent source code formats from stack providers, such as Stonestreet One.

Integrated Solutions
In a Windows™ or PocketPC-based environment, a Pentium™ or ARM processor actually executes the upper stack functions, which are usually included as part of some Bluetooth software applications.

In an embedded application, the Bluetooth upper stack and host processor function must be accounted for in some other way, typically with an embedded core.

The host processor performance requirements for supporting the Bluetooth protocol are minimal, usually less than 1 MIPS. Thus, it is very easy to add Bluetooth support to an embedded application if the host processor has processing bandwidth and a Bluetooth stack is available for the targeted processor.

The 150 D-MIPS performance of the MicroBlaze soft-processor core means the additional 1 MIPS of processing overhead can often be accommodated with relative ease.

The availability of the Bluetooth protocol stack presents a bigger obstacle, because the stack must be ported to the targeted embedded processor. However, with the introduction of the Memec Design Embedded Bluetooth Development Kit, this issue has been addressed for any MicroBlaze-based system.

The Embedded Bluetooth Kit
The Memec Design kit provides all the necessary components to build and test a Bluetooth system:

• An evaluation version of the Bluetooth stack ported to the MicroBlaze core
• A Spartan-IIE development board
• Two P160 Bluetooth modules
• An evaluation version of the BTExplorer™ Windows application
• Xilinx EDK software
• Cables
• Power supplies
• Documentation.

Figure 2 shows a typical setup of the Bluetooth kit.

A simple point-to-point radio system can be created with the kit components and a Windows-based PC. One end of the communication system is created with a standalone P160 Bluetooth module connected via USB or RS232 to a Windows PC. This PC runs the evaluation version of the BTExplorer application, which exe-cutes the Bluetooth stack within the Windows environment.

The other radio system uses the Spartan-IIE board and second P160 Bluetooth module. The Spartan-IIE platform implements a MicroBlaze design, combining the evaluation Bluetooth binary stack and serial port profile with your application code. An optional second PC connects to the Spartan-IIE board for user feedback and control.

Figure 3 shows the functionality of the P160 Bluetooth module based on Broadcom’s BCM2035 – a monolithic, single-chip, baseband processor with an integrated 2.4 GHz transceiver for Bluetooth v1.1 and 1.2 applications. It minimizes the footprint and system cost of implementing a Bluetooth link by integrating all critical components into the device.

The BCM2035 is an ideal solution for any voice or data application that requires the Bluetooth standard Host Controller Interface (HCI) via either UART or USB, and PCM (pulse code modulation) audio interfaces. The integrated microprocessor unit stores the lower level protocol stack in ROM plus patch RAM to provide the maximum flexibility while eliminating the need for external flash memory for the lower stack.

The BCM2035 radio transceiver provides enhanced radio performance to meet the most stringent industrial temperature applications or the tightest integration into portable devices. It provides the highest available radio performance of any single-chip device with -90 dBm sensitivity and +7 dBm programmable output power.

Development System Capabilities
The Spartan-IIE board from Memec Design provides all the necessary features for implementing a simple MicroBlaze design. The board includes the P160 expansion module slot for connection to the P160 Bluetooth module, SDRAM, serial port, and miscellaneous support circuits.

Figure 4 shows an example MicroBlaze system that incorporates the Bluetooth interface. Because the Bluetooth module looks like a standard serial port to the MicroBlaze system, the only hardware modification required to the system architecture is the addition of a UART block.

The Memec Design Embedded Bluetooth Development Kit includes a fully functional evaluation version of Stonestreet One’s Bluetopia™ protocol stack. An implementation of the upper Bluetooth protocol stack, the Bluetopia software eases application development by providing a robust yet easy-to-use development tool that implements the Bluetooth protocols above the HCI.

The Bluetopia application programming interface (API) provides access to the upper-layer protocols, including Logical Link and Adaptation Protocol (L2CAP), Service Discovery Protocol (SDP), RFCOMM protocol, and OBEX protocol. Bluetopia software also provides APIs for all mandatory and most optional profiles.

In addition, Stonestreet One provides lower level HCI transport drivers to interface to various Bluetooth devices such as the BCM2035. These lower level HCI drivers have been written to support the addition of new HCI transport drivers with little or no change to existing applications.

The evaluation version of the Bluetopia protocol stack provides support for the following Bluetooth protocols: HCI, L2CAP, SDP, and RFCOMM. The Bluetopia stack also provides support for generic access profile (GAP) and serial port profile (SPP) Bluetooth profiles. Figure 5 illustrates an example Bluetooth protocol stack.

In addition to the above listed protocols and profiles, Stonestreet One will make available an extensive suite of existing and future Bluetooth protocols/profiles as required. Full development or production versions are available through license from Stonestreet One along with additional profiles if required.

BTExplorer is a user-friendly Windows application that is used to connect and manage Bluetooth devices. BTExplorer discovers Bluetooth devices in the vicinity and presents them in an easy-to-understand format similar to Windows Explorer.

As used in the development kit, BTExplorer facilitates a simple peer-to-peer system. When connected to the standalone P160 Bluetooth Module, BTExplorer provides the upper stack capability to the module, thus creating a complete Bluetooth node.

Conclusion
The Memec Design Embedded Bluetooth Development Kit allows designers to enhance any new or existing MicroBlaze-based designs with the addition of a Bluetooth interface. By providing a MicroBlaze-specific port of the Bluetooth stack along with the necessary prototyping hardware, the kit eases the development process, shrinks the design cycle, and speeds your time to market.

The Embedded Bluetooth Kit is available for $1,495 from Insight Memec at www.memec.com/insight-memec/. Plans are under way to develop a similar development kit utilizing the new Xilinx Spartan-3 FPGA.

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