When the Effects Controller starts playing the first lighting effects file on its own SD card, it send a command to the MP3 player to play file 0.mp3. When the EC starts the next lighting file, it tells the MP3 player to play file 1.mp3, and so on.
The MP3 player reads files from an MMC, SD, or SDHC card. The card must be formatted as FAT or FAT32. Up to 100 files are supported by the controller (though the Effects Controller only supports 50). The files must be named 0.mp3, 1.mp3, 2.mp3, etc up to 99.mp3.
The audio is output via a 1/8 inch stereo jack. Headphones or an external amplifier can be plugged in.
Control is via an RJ45 jack implementing the DMX RJ45 standard pinout (pin 1 D+, pin 2 D-, pin 7 and 8 Ground). Normally you would connect a standard ethernet type cable from the MP3 player to port 4 or 5 on the Effects Controller. The MP3 player has a built-in DMX termination resistor and so should be the last controller on a DMX network. A jumper on the PCB marked TERM can be cut it this is not wanted.
Part of the MP3 player is made by Rogue Robotics and is described here in detail for those that need additional info on what it supports. The DMX control part was added by Minleon.
'P' # P followed by a single byte (binary file#). Starts playing file "#.mp3" from SD card. 'M' 'P' 'S' Three bytes, "MPS". Stops playing current file. 'M' 'P' 'V' # Four bytes, sets volume level from 0-254. 0=loudest. 16=default.