Audio Innovators

AI502RADA MP3 RS232 playback module

Features:

- plays *.mp3 files from CompactFlash memory.

- implements a subset of the Mackenzie RADA / ATO instruction set

- standard (+/-10V) RS232 control input

- 100mW/channel drive output

General description:

The AI502RADA series playback modules use MP3 (MPEG I, layer 3) perceptual coding to reproduce sound at a variety of data rates and quality levels. At the standard music rate of 128000bps, the system can produce near-CD quality sound using approximately one megabyte of data per minute. The systems can also accept lower data rate and monaural files, so capacity can be extended if an application does not need the full capability for all sounds. Data rate may be raised to as high as 320kbps for higher quality sound.

The system has been optimized for industrial use in the following ways:

- the control interface is RS232 plus two programmable input/output lines.

- the memory interface is for CompactFlash format flash memories. This style of memory is much more rugged than the smaller formats used for consumer MP3 players. It is also available in larger capacities; up to 1Gbytes, or 18 ½ hours of continuous stereo sound.

- the memory cartridges use standard Windows formats. A standard CompactFlash programmer  is used to program the memories.

The audio section uses a VLSI Oy VS1001k decoder, affording full volume and balance controls although in this implementation volume is set to maximum and balance to center. It accepts 1200B RS232 commands and produces volume-controlled stereo headphone level outputs. The firmware can read standard Windows directory structures (FAT 16 and 32) and fragmented files. The core accepts +5V and generates independent regulated 3.3V analog and digital supplies for the cleanest possible sound.

 The CompactFlash memory can be hot-swapped. The system will recognize that a new cartridge has been inserted and will re-initialize itself within about four seconds. A falling pitch double-beep indicates memory removal and a rising pitch set will signal that the unit is ready to play again.

AI502RADA RS232 Command Set:

Commands are transmitted as 8-N-1, 1200B, standard level (+/-10V), RS232. 

Commands may be in upper or lower case ASCII or a mixture of the two. The numeric file indicator can be from one to three decimal digits. A space can be left between the command and number, but is not necessary. All commands must be followed by a carriage return <0x0d>..

Only five commands of the RADA / ATO set have been implemented:

Playing files:

 File play is initiated from by one of three RS232 commands:

·         PLI <n> causes file n to be played immediately. If another file is playing, that file is stopped and file n begins. 

·         PLN <n>, play next in queue, causes file n to be inserted at the head of the current queue. If the queue is currently empty, file n is played immediately.

·         PLQ <n>, play last in queue, causes file n to be added to the end of the current queue. If the queue is currently empty, file n is played immediately.

Stopping play:

 Play can be stopped by issuing the stop (STP), or stop all (STP ALL) commands. STP stops the current file. If other files remain in the queue, they are played as usual. STP ALL stops the current file and clears the queue.

Command return strings:

The AI502RADA returns an echo of the command sent followed by two carriage returns, a line feed, and the prompt “Rada>”. For example, if the command is pli4, the return is:

pli4<cr><cr><lf>Rada>

For file numbers greater than 10, the last digit of the file number is appended – for PLI 14, the return is:

PLI 14<cr><cr><lf>Rada>4

AI502RADA Connections:

 The AI502NAI has only three connectors –

·         RS232 controls are supplied via a 25 pin d-sub female jack. Rxd pin 3, Txd pin 2, Ground pin 1.

·         Power input via 2 post term block(12-35 vcd).

·         The stereo audio output is delivered via a 1/4” stereo style phone jack. The left channel is on the tip, the right channel is on the ring, and system ground is on the sleeve of the connector.

Electrical Characteristics:

Absolute Maximum Ratings:

Stresses above these limits may cause permanent damage to the system. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may effect device reliability.

DC Characteristics: standard operating temperature 0°C < TA  < +85°C

Power supply to the 502 card via a dc to dc converter.   

Control lines TXD, RXD

AC Characteristics: standard operating temperature 0°C < TA  < +70°C

Online Support:

Audio Innovators maintains the latest specifications, schematic diagrams, and support software in the support section of our website, www.AudioInnovators.com/support.htm.

For questions not answered there or for other inquiries, please write us at support@AudioInnovators.com, or call 1-813-671 3800

Revision 1.24, October 20, 2005.