Carriage Return or Line Feed using RS-232

RS232 strings ending in \r will be replaced with a carriage return.
RS232 strings ending in \n will be replaced with a line feed.

RS-232 troubleshooting tips

The S-Play is set up to receive RS-232 triggers in the form of ASCII strings. 

When connecting RS232 from a transmitter directly to the S-Play via the 2 x DB9 ports, a Null Modem Cable should be used, to ensure the TX of the transmitter is connected to the RX of the S-Play. Vice versa if the S-Play is being used to send RS232 events to other devices, the TX on the S-Play should be connected to the RX of the receiving device. 

Some transmitters add characters to the end of a desired RS232 command. For example, some KNX-RS232 gateways add:

"=" is an allowable character as part of your RS-232 string for a trigger in the S-Play. If for example your desired trigger string is "SHOW1" and the gateway adds to this such that the trigger string becomes "SHOW1=1" as long as your KNX gateway is able to send the same "SHOW1=1" string each time and not change the value to "SHOW1=0" etc.  then you can also create a trigger in the S-Play to match the string "SHOW1=1" and it will be able to accept the trigger once that string is received.

Trigger latency

Latency depends on two main factors

  • Triggering Method: If using GPIO electromechanical relays there can be a tiny bit of variance introduced, usually in the millisecond range.
  • Internal Processing: There’s a 10-20ms delay after a trigger is received to load the playlist from the database and open dynamic cues. Playback states are checked every 8ms; Internal processing can be up to 28ms max.


Connecting to the S-Play's GPI

The four GPI ports on the rear of the S-Play can be used to attach virtually any dry contact input device or sensor, or switch.

The S-Play GPI provides its own voltage and detects when a switch contact is closed.

As of firmware version 1.5.0 (April 2021) and onwards, the digital inputs are settable to trigger on break, or trigger on make - letting users set up trigger conditions based on the GPI being in an open state or closed state.

Power should never be fed into or connected to the GPI connectors.

We recommend a maximum cable distance of 100m between the S-Play’s port and it’s 0v (GND) – i.e. if you’re using a 2 core cable with a switch at the end your cable length would be half of this (50m) to ensure the full circuit length is 100m. Although as a rule of thumb the shorter the cable the better to reduce any risk of RF interference or capacitance build-up. Where possible when triggering the S-Play it’s always good to make contact for at least a second instead of a short sharp click of a button for longer cable runs.

The S-Play has a threshold to detect circuit completion of any resistance under 20 Ohms.

For more installation instructions for wiring, the relays and GPI see the user manual.

Mains input from an old lighting circuit (Retrofit):

  • Useful when retrofitting an installation. Use the existing power infrastructure to trigger and stop an S-Play Playlist.
     Receive mains power in a contactor then wire the dry contact GPIO to an S-Play GPI Trigger.
  • Mains input, convert to a dry contact closure using a mains contactor. Example product:
  • Never wire mains AC directly into the S-Play

Pressure Sensors:

PIR / Occupancy sensors:

  • Good for detecting someone walking into a space installation.
     As long as it is Dry contact, (i.e. doesn’t send power down the Connection line when triggering), it will work with the S-Play.
  • If your motion sensor does send power when activated, convert it to a dry contact by using an intermediary relay or contactor linked above.
    Example product:


  • Push button switches, or relays are great for acting as a physical interaction with the S-Play. – Part of an escape room, control panel, or a simple analogue way to connect control systems.
  • Momentary switches, (ether push to break or push to make) are ideal for this function.
  • Alternate switches - since the S-Play GPI can be set to trigger based on open or closed state, this meshes nicely with alternating switching, where the "ON" state of the switch can be set as a playlist start trigger, and the "OFF" state of the switch can be set to an "OFF" trigger. 


  • If you wanted to trigger the S-Play as part of a DALI system you could look at wiring one of your GPI connectors to a DALI Relay. Opening and closing the relay (from a series of button panels and switches could trigger a playlist on the S-Play.


Digital inputs devices

The S-Play's 4 digital inputs are dry contacts. As such, no voltage should be applied to these from an external source to trigger them.

When integrating the S-Play as part of a wider system, ensure devices connected to the digital inputs only complete the circuit.

Examples of circuit completion include:

  • Switches
  • Relays
  • Sensors that close a circuit (i.e. PIR with inbuilt relays)
  • Pressure pads that close a circuit.

If the trigger source you want to use with the S-Play sends voltage when it is active, a relay can be used to turn this power into a switch action that will isolate the S-Play from the external voltage while still triggering your S-Plays playlist.

If there is voltage present in the circuit as part of the device being used as a trigger (switches/relays), you will need to convert the voltage from the switch/relay into something that sends no voltage. This can be done either by a Contactor or a non-latching Relay (a component that can open or close a circuit if power is applied to an electromagnet. - Basically an electromagneticswitch)

As long as the voltage is low (under 12v), a non-latching Relay’s likely to be the best and inexpensive option. An example product can be found here: 12V Handy Little Relay. For wiring, please consult the Contactor or a non-latching Relay documentation - an example of wiring a non-latching Relay can be found below.

From the diagram, connect your 12v input to the 12vDC input of this relay (primary coil) and connect the S-Play’s digital input and gnd to the other. (the diagram shows the ability wire higher voltages to it, but this won’t be relevant in this use case).

Digital Inputs cabling

The S-Play’s Digital Inputs detect circuit completion when they are connected to the S-Plays ‘GND’ (0V- terminal).

The maximum resistance of a cable run that still allows a trigger to be detected is 20Ohms.

The longer the cable connected, the higher it’s capacitance and likelihood of interference from EMF.

To ensure a reliable trigger, contact should be made for at least 3 seconds when triggering a Digital Input.

Always run digital input cabling away from mains power or high sources of EMI (i.e. air conditioning units) to reduce interference.

ENTTEC recommends a total maximum wire length of 100m (50m total distance from the S-Play). providing it’s total resistance is under 20 Ohms.