Messaging / MQTT

void MQTTsetGroup(String group)

Sets the MQTT group where all messages are sent and all subscriptions are done.

Can be used to easily separate different applications/users/groups

e.g. specify one group per game or one group per boards playing in the same game.

void MQTTonMessage(void (cb)(String &topic, String &message))

Sets the callback function that is called one a MQTT message is received for one of the subscribed topics.

needs a callback function with signature:

topic - String topic on which the message was received
message - String content of the received message.

boolean MQTTpublish(const char topic[], String message)

Publishes/sents a message to the specified MQTT topic.

if an MQTT group is set, the topic is automatically preceded with this group string.

topic - topic to which the message will be sent
message - content of the message.

boolean MQTTpublish(String topic, String message)

Publishes/sents a message to the specified MQTT topic.

if an MQTT group is set, the topic is automatically preceded with this group string.

topic - topic to which the message will be sent
message - content of the message.

boolean MQTTsubscribe(const char topic[])

Subscribes to the specified MQTT topic. Once a message is received for a subscribed topic, the MQTTonMessage callback is called.

If an MQTT group is set, the topic is automatically preceded with this group string. see https://www.hivemq.com/blog/mqtt-essentials-part-5-mqtt-topics-best-practices for more information on topic subscriptions.

topic - topic to subscribe to

boolean MQTTsubscribe( String s_topic)

Subscribes to the specified MQTT topic. Once a message is received for a subscribed topic, the MQTTonMessage callback is called.

if an MQTT group is set, the topic is automatically preceded with this group string. see https://www.hivemq.com/blog/mqtt-essentials-part-5-mqtt-topics-best-practices for more information on topic subscriptions.

topic - topic to subscribe to

boolean MQTTunsubscribe(const char topic[])

Unsubscribes from the specified MQTT topic.

if an MQTT group is set, the topic is automatically preceded with this group string.

topic - topic to unsubscribe from

void MQTTconnectRGB()

Subscribes the Kniwwelinos RGB LED to specific MQTT topics. If a message is received, the LED color will be changed.

if an MQTT group is set, the topic is automatically preceded with this group string.

The board will listen on group/RGB/COLOR for messages.

Message format:

“FF00FF”, first 2 digits specify the RED, second the GREEN, third the BLUE component.

void MQTTconnectMATRIX()

Subscribes the Kniwwelinos MATRIX to specific MQTT topics.

if an MQTT group is set, the topic is automatically preceded with this group string.

The board will listen on group/MATRIX/ICON for icons. If a message is received, the ICON will be displayed.

Message format:

“B1111100000111110000011111” 25 pixels binary one after the other, prefix B or
“0x7008E828A0” one byte for each 5px row, prefix 0x

The board will listen on group/MATRIX/TEXT for icons. If a message is received, the Text will be displayed.

Message format:

“Hello World!”