Development board enables experimentation with audio file formats

The new development board features an ARM Cortex-M4 microcontroller with audio file decompression software, a choice of high end and low cost d/a converters, a codec and digital and analogue microphones. According to Future, by using the board's free pc based graphical user interface, which connects to the board via USB, developers can start recording and playing back audio files in minutes. The board is also designed to provide a hardware environment in which to develop code and evaluate the performance of ARM Cortex-M4 application software. At the heart of the new board is Freescale's MK60N512VMD100 microcontroller, a member of the K60 Kinetis family of products. With the free MQX rtos and a free USB stack pre-loaded on the microcontroller, the board is designed to provide a highly capable general platform for ARM Cortex-M4 development work. For system level prototyping, it can be interfaced to Future Electronics' LongBow Future-Blox motherboard. The board's software uses the ARM DSP CMSIS library, which has been optimised for the dsp coprocessor available on the ARM Cortex-M4 core. The specialist software and peripheral features on the Audio Streamer Micro-Blox make it suitable for the rapid development of digital audio equipment proofs of concept. Audio file decoding software embedded in the microcontroller can handle mp3, FLAC, WAV and Ogg Vorbis file types. FLAC, a 'lossless' file format, is becoming popular in hi-fi equipment in which excellent sound reproduction and very low distortion are of paramount importance. Ogg Vorbis is an open source, royalty free file format that achieves tighter compression than mp3 and is used in embedded and industrial audio applications in which the emphasis is on reducing the requirement for memory. Future adds that the K60 microcontroller also has the processing power to run other software for decoding files such as ALAC, WMA, AIFF and AAC. An Ethernet connection for file downloading is provided via the KSZ8031RNL, a small, low power Ethernet transceiver from Micrel. Audio playback of the decoded files is via one of two Wolfson Microelectronics d/a converters: the high end WM8741 is intended for use with FLAC files for high sound quality. The WM8741's outputs are buffered by high end quad audio op amps. The on board power supply uses small buck and boost regulators from Micrel, but the board also provides a terminal block for the connection of an external audio quality power supply. The board's other, lower cost d/a converter, the WM8524, is suitable for use with Ogg Vorbis, WAV and mp3 files. It also includes three 3.5mm stereo sockets for connection to external speakers. For highly integrated applications, Wolfson's WM8904 ultra low power codec is also available, offering an a/d converter, d/a converter, ReTune digital audio processing functions and headphone amplifiers. Two digital microphones and a single analogue microphone interface to the WM8904 for sound recording. According to Future, the board is intended as a proof of concept development platform, for use in early prototyping. The company has made available all relevant design information including Gerber design files, schematics and bill of materials. Colin Weaving, technical director of Future Electronics (EMEA), said: "Future Electronics is convinced that ARM Cortex-M4 is going to be a massive hit with our industrial and embedded customers and this board is a brilliant starting point for anyone thinking of developing on a Kinetis micro. Future Electronics has also given developers all the essential hardware components and decoding software that they need to do an audio proof of concept development, whether it's for a €3,000 hi-fi device or a cheap voice alert system embedded in a lift." The Audio Streamer Micro-Blox board is available free to qualifying customers of Future Electronics.