Apartment living has its drawbacks. Often, you can't have pets, and even more exasperating to some, you cannot install your own rooftop satellite dish! San Diego based X-Digital Systems is about to change that with its new MSL384 Integrated Satellite Receiver with FM modulator, an audio broadcast media receiver/decoder product designed for deployment in multi-dwelling units (MDUs), a.k.a. apartment/condo complexes. With this product, operators can sign up subscribers living in MDUs without having to somehow install satellite dishes in each and every apartment/condo. Subscribers can then enjoy music and information broadcasts.

For its new product, X-Digital needed a low-cost, low-power signal processor that could decode high-density MPEG streams. The company chose Blackfin® ADSP-BF531 processors from Analog Devices, Inc. (ADI) due to the processors' superb price/performance and exceptional power saving features, which were especially important as 48 processors are housed in each unit.

Satellite Broadcasts
X-Digital designs, manufactures, and sells satellite and terrestrial multimedia communications systems. The company specializes in advanced communications systems for both wireless and wired applications that are designed for reliability, flexibility, and quality. X-Digital provides media distribution to end users using both Ethernet and Coaxial cable as physical mediums for its MDU customers.

X-Digital whose market at this point is solely in Japan (later the company plans to sell its products in the U.S.), was selling a digital satellite receiver that enabled operators to receive satellite signals at a central location for distribution to their own customers over terrestrial lines they did not own. New legislation, however, meant that the owners of the lines began to charge X-Digital's customers enormous sums for the use of the transmission lines. X-Digital's new MSL384 solves this problem, as the receiver can be installed directly into a MDU. While operators won't be able to completely eliminate all of the leasing costs, with X-Digital's new product, they will realize significant cost savings.

With the new product, operators can receive the digital audio programming from the satellite at individual MDUs and distribute it to the apartments/condos through the existing Coaxial cable infrastructure. The MSL384 receiver converts the digital audio satellite signals to FM analog signals. Essentially, the MSL384 receiver provides live decoding of satellite-based digital audio broadcast media.

Blackfin Processor's Superb Price/Performance
X-Digital teamed with ADI for state-of-the-art ADSP-BF531 signal processors. ADI recommended Epigon, a long-time ADI third-party software provider based in Bangalore, which specializes in the development of codec solutions for the multimedia market. Epigon developed an MPEG2 (MPEG 1 layer 2) decoder for multiple channels to run on the Blackfin processors. X-Digital then licensed the MPEG2 code from Epigon.

The Blackfin ADSP-BF531 processors are used as high-density MPEG2 decoders. Each MSL384 device houses 3 printed circuit boards (PCBs), each with 16 Blackfin ADSP-BF531 processors for a total of 48 Blackfin processors per system. Each MSL384 receiver decodes 384 MPEG streams. X-Digital said that pure economics was the main driver in the selection of the Blackfin ADSP-BF531 processor, as the company's high-volume application required a very low cost per decoded stream. In addition, with its 400 MHz of performance and 52K bytes of on-chip memory, the Blackfin ADSP-BF531 processor provided the right amount of price/performance X-Digital needed for its application.

The Blackfin ADSP-BF531 processor is a member of the Blackfin family. Blackfin processors incorporate the Micro Signal Architecture (MSA) and embody a new type of 16/32-bit embedded processor designed specifically to meet the computational demands and power constraints of today's embedded audio, video, and communications applications. The processors deliver breakthrough signal processing performance and power efficiency with a RISC programming model, presenting high performance, homogenous software targets, which allow flexible resource allocation between hard real-time DSP tasks and non real-time control tasks.

For X-Digital, the Blackfin processor's unique combination of processing attributes eliminated the need for separate digital signal and control processors, reducing bill of materials (BOM) costs. X-Digital said this was one of the reasons it was able to cost-effectively integrate the 48 Blackfin ADSP-BF531 processors per MSL384 unit. Using the Low Profile Quad Flat Package (LQFP) also helped X-Digital achieve greater board density in a cost-effective manner as the package does not require additional costly layers and allows for the inclusion of a memory chip directly behind the Blackfin ADSP-BF531 processor.

As time-to-market and cost-savings were both key to the success of the company's project, Blackfin excelled once again by offering industry-standard interfaces with a high performance signal-processing core. For system peripherals, the Blackfin ADSP-BF531 includes a UART port, an SPI port, two serial ports (SPORTs), four general-purpose timers (three with PWM capability), a real-time clock, a watchdog timer, and a parallel peripheral interface (PPI). In addition, the Blackfin ADSP-BF531 includes high-speed serial and parallel ports for interfacing to a variety of audio, video, and modem codec functions, and an interrupt controller for flexible management of interrupts from the on-chip peripherals or external sources. The Blackfin ADSP-BF531 processor also includes an on-chip voltage regulator in support of the processor's dynamic power management capability. The voltage regulator provides a range for the output (core voltage) of 0.85V to 1.2V. The voltage regulator can be bypassed at the user's discretion.

X-Digital leveraged the Blackfin processor's SPORTs and SPI ports. X-Digital used the SPORTs in Time Division Multiplexed (TDM) mode, configured for 16 bits per channel and a total of 16 channels. This allows one peripheral to send out 16 bits of digital audio — voice or music — via 16 channels in real time, without "pops" or "clicks."

All of the peripherals, except for the general-purpose I/O, real-time clock, and timers, are supported by a flexible DMA structure. There is also a separate memory DMA channel dedicated to data transfers between the processor's various memory spaces, including external SDRAM and asynchronous memory. X-Digital took advantage of both external and internal memory as a buffer and for code space.

Distributing many channels of audio over a cable requires the high speed and linearity provided by the AD9726, a 16-bit DAC, and the ADL5330, an RF variable gain amplifier. The ADT7476, a fan controller, and several temperature sensors using ADT75 provide other system support.

Thermal Dynamics
Power consumption was definitely a challenge with 48 signal processors on board each MSL384 device. Here's where Blackfin came to the rescue. Blackfin processors provide world-class power management and performance. Designed in a low power and low voltage design methodology, Blackfin processors provide the ability to vary both the voltage and frequency of operation to significantly lower overall power consumption. X-Digital said this feature is critical for managing the thermal limits of the MSL384 unit.

For tools, X-Digital used ADI's EZ-KIT Lite Evaluation System, which includes a board, cable, power supply, documentation and a license key. EZ-KIT Lite is a low-cost hardware platform that includes a Blackfin processor surrounded by several other devices such as audio codecs, video encoders, video decoders, flash, SDRAM, and more. Each EZ-KIT Lite board also includes and on-board JTAG emulator with a USB 1.1 connector and a standard 13-pin JTAG header for use with high-performance emulators available from ADI. Via the processor's JTAG port and the VisualDSP++ software, a project management environment, users can set breakpoints, single step through code, view memory, fill/dump memory, perform real-time data manipulation, profile execution and memory access, plot data and use standard I/O.

The beauty of the Blackfin processor's architecture is that it includes advanced memory management that supports both memory-protected and non memory-protected embedded operating systems, giving companies, such as X-Digital, a choice of operating systems. These could include uCLinux, or INTEGRITY, or velOSity from Green Hills Software, to name only a few. For this project, X-Digital used ADI's VDK, the preemptive multitasking VisualDSP++ Kernel that incorporates scheduling and resource allocation techniques tailored specifically for the memory and timing constraints of DSP programming. It offers tight integration VisualDSP++, no license fees, and a royalty free RTOS. X-Digital plans to use tools from Green Hills for future designs where a RTOS that includes more features than VDK offers is required.

Providing audio service to apartment and condo complexes via satellite is a fast-growing market, and until now, operators have been limited in their ability to offer it. Thanks to the Blackfin processor's convergent processing abilities — the ability to provide low cost yet high-performance signal and control processing in a single architecture — X-Digital is offering it's new MSL384 Integrated Satellite Receiver. Soon consumers residing in apartment/condo complexes in Japan and later in the U.S. will be enjoying the benefits of these satellite-based digital audio broadcasts.

For more information, please visit X-Digital Systems.

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