Firmware is unchanged from Elm Chan

255-Voice PCM Sound Generator

http://elm-chan.org/works/sd20p/report.html

Supported sound file format is RIFF/WAVE in LPCM, 8/16bit, mono/stereo and 8kHz-48kHz. Any other sound files, such as ADPCM, MP3 and AAC, must be converted into the PCM. The sound files must be named NNN.wav. The NNN is three digit number in range from 001 to 255. The sound files must be put into the root directory.

The control command is input as binary code by eight contacts (SW1-SW8) and the corresponding sound file will be played. e.g. SW1 corresponds to 001.wav, SW4 corresponds to 008.wav and SW1+SW5 corresponds to 017.wav. There are four operating modes, behavior of the sound generator on control command, can be configured by 000.txt on the root directory. Each mode works as follows:

Mode 0 : Level trigger

Plays a sound file corresponds to the input code in auto-repeat. When the input code is changed, the sound also be changed. When the input goes off(0), the audio output is stopped.

Mode 1 : Level trigger (sustained)

Same as mode 0 but the file is played until end of the file and then stopped when the input goes off.

Mode 2 : Edge trigger

Plays a sound file corresponds to the input code once. Any code change while a sound will be ignored.

Mode 3 : Edge trigger (re-triggerable)

Same as mode 2 but the code change is accepted while the sound. To re-rtigger with the same code, change input to 0 and then input the code again.

Mode 4 : Edge trigger (stop on release)

Same as mode 2 but the sound stops when the input goes off(0).

The LED indicates that a sound file is being played. It also flashes on any error. The number of flashes + a second of blank corresponds to the type of errors as follows:

• Two fhash - I/O error. (hard error or file system error)
• Three flash - The sound file is not found.
• Four flash - Invalid sound file.