MQTT_SUR40

Broadcast input events from a PixelSense table (SUR40) to a MQTT message broker and to UDP.

MQTT and UDP

The first idea was to use MQTT, but it's to slow. So the second thought was about using UDP. It's still too slow, but it's better.

Documentation

The messages are published on the topic SUR40/{Id} by default. Subscribe to SUR40/+ to receive the events in JSON.

When a touch input is finished/removed, a new empty message is published on SUR40/{Id}.

All the messages are non persistent and the quality of service (QOS) is 1 (at least once).

{
    "Id": 16842750,
    "Type": "Finger",
    "X": 583.97,
    "Y": 329.99,
    "Orientation": 270.0,
    "Width": 25.97,
    "Height": 39.99
}

{
    "Id": 16842749,
    "Type": "Blob",
    "X": 640.0,
    "Y": 313.98,
    "Orientation": 0.0,
    "Width": 101.97,
    "Height": 67.99
}

{
    "Id": 16842747,
    "Type": "Tag",
    "X": 882.0,
    "Y": 159.99,
    "Orientation": 0.0,
    "Width": 0.0,
    "Height": 0.0,
    "TagSchema": "00000000",
    "TagSeries": "0000000000000042",
    "TagExtendedValue": "0000000000000000",
    "TagValue": "0000000000026773"
}

UDP format

The UDP format is in binary, and the endianess is the same as the surface table. It doesn't contain tag data yet, and when a touch is finished/ended, only the int32 id is sent.

struct SUR40_DataFormat {
	int32 Id;
	float X;
	float Y;
	float Orientation;
	char Type;
};

How to display an external video input while still receiving touch input events

When you select the external video input on the SUR40 device, Windows still runs in the background but stops receiving touch input events. You can open the table and connect the HDMI output from the PC mainboard to the screen HDMI IN, and connect your external video HDMI cable to the HDMI port where the SUR40 PC was connected to.