MP3 Trigger Hookup Guide V24

Contributors: Joel_E_B, robertsonics
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Using the Trigger Inputs

The MP3 Trigger provides 18 input pins (TRIG01 –TRIG18) that can be used to trigger specific MP3 tracks on the microSD card. MP3 tracks are associated with triggers by placing a 3-digit number (using leading 0s) at the beginning of the filename; 001 for TRIG01, 002 for TRIG02 and so on. The rest of the filename can be anything. For example, the following are both valid names for TRIG14:

  • “014TRACK.MP3”
  • “014 Breaking Glass.mp3”

The trigger inputs are active low and pulled high internally. Therefore, they can be activated either by digital outputs from another microcontroller (such as an Arduino) or by a simple contact closure (switch) to ground. The inputs support voltage levels of either 5V or 3.3V.

The trigger inputs are made available on the even-numbered pins of a dual row connector, and all the opposing (odd-numbered) pins are ground, making it easy to wire individual switches or contact closures directly to the MP3 Trigger board.

Installing a 36-pin dual-row header allows shunt jumpers to be installed on the trigger inputs to automatically sequence and loop tracks on power-up as follows.

When a triggered track reaches the end, the MP3 Trigger looks to see if any trigger inputs are active, and will automatically start another track if so. If only the same trigger is active, then that track will restart (loop). If other triggers are active, the MP3 Trigger will always start the next higher trigger track, wrapping back to 1 after 18.

This, combined with the fact that the MP3 Trigger will automatically start the lowest numbered active trigger on power up, means that by installing shunt jumpers on the trigger inputs, the MP3 Trigger can be set to automatically sequence and loop from 1 to 18 tracks on power up with no externally programming or control required. (Beginning with firmware version 2.40, installing a shunt jumper on a single sequential trigger will do the same thing.)

For example, if you wanted track 9 to play on startup, you'd jumper trigger 9. If you wanted tracks 1 through 9 to play on startup, you have to have a jumper on all nine triggers.

Using the initialization file describe later in this document, triggers can be reprogrammed to start sequential or random tracks. For example, if a trigger is reprogrammed to be a random trigger, and that one trigger is shunted closed, then the MP3 Trigger will power up and continuously play tracks in a (pseudo) random order.

Quiet Mode

The MP3 Trigger can be placed into Quiet Mode using the serial control port. In this mode, the trigger inputs will not start tracks but instead will cause serial messages to be sent upon activation. (See “MP3 Trigger Outgoing Message Summary” below.) This allows the trigger inputs to be decoupled from specific tracks, so that a PC or microcontroller can monitor the trigger inputs and then start any track or sequence of tracks via the serial control port.

Quiet Mode is off by default and is not preserved through a power cycle