Component: MQTT Client (Comms: IoT/Cloud)

Author	Matrix TSL
Version	1.1
Category	Comms: IoT/Cloud

MQTT Client component

A component providing access to MQTT IoT client. The client can connect to a MQTT server such as ThingSpeak. Allowing IoT type data to be published and read back.

Detailed description

No detailed description exists yet for this component

Examples

The MQTT component requires connection to a Network Comms component via the "Network Component" property, to provide the bridge for simulated TCP/IP communication.

The Network Comms component can then be linked to an embedded TCP/IP component to provide embedded TCP/IP support.

Here is a typical setup for using MQTT on a Raspberry Pi.

Local Weather

A simple example demonstrating how to use MQTT with Flowcode SCADA to get the local weather conditions.

The example shows temperatures from Halifax in the UK and from Sydney in Australia.

SCADA BBC TEMPERATURES

Publish

Raspberry Pi

Here we have an embedded Raspberry Pi project connected to an I2C Sensor, the sensor is sampled and the data is published to a MQTT server.

RPI3 MQTT IOT EBM016

ESP8266 Module

Here we have an embedded project using an ESP8266 wifi module, an analogue input is sampled and the data is published to a MQTT server.

MQTT IOT ESP8266

Subscribe

ESP8266 Module

Here we subscribe to a topic and receive it back into Flowcode embedded using an ESP8266 module.

Subscribe ESP8266 MQTT

Flowcode App Developer

Here we subscribe to a topic and receive it back into Flowcode App Developer.

Subscribe App Developer MQTT

Making your own Raspberry Pi based MQTT Broker

Click here for instructions on creating your own Raspberry Pi MQTT Broker.

Downloadable macro reference

	GetTopic
Get the Topic of the last received (Read) packet. Returns the number of bytes for the Topic
- STRING	Topic
- BYTE	Size
Byte count the Topic buffer
- BYTE	Return

	ErrorAsString
- BYTE	Error
- STRING	Return

	Connect
Connect to the MQTT Server. Returns the connected state. 0 if not connected, 1 if successful connection, or already connected.
- BYTE	Return

	Publish
Publish data to the server (broker) Returns non-zero if successful
- STRING	Topic
- STRING	Payload
- BYTE	Return

	LastError
Returns the last error
- BYTE	Return

	Read
Read incoming data. Returns non-zero if packet received. Use GetTopic and GetPayload to read the contents.
- UINT	Return

	Disconnect
Disconnects from the MQTT server and the network
- BYTE	Return

	Ping
Ping packet is sent to the Server and checks for a reply. Returns non-zero value if successful
- BYTE	Return

	GetPayload
Get the Payload of the last received (Read) packet. Returns the number of bytes for the Payload
- STRING	Payload
- BYTE	Size
Byte count the Payload buffer
- BYTE	Return

	Subscribe
Subscribe to a Topic. Must be Connected first Returns non-zero if successful
- STRING	Topic
- BYTE	Return

	Unsubscribe
Unsubscribe from a Topic. Must be Connected first Returns non-zero if successful
- STRING	Topic
- BYTE	Return

	Initialise
- VOID	Return

	GetPayloadString
Get the Payload of the last received (Read) packet as a string value
- STRING	Payload
- BYTE	Size
- BYTE	Return

	Initialise
Starts up the MQTT component - call this after initialising the NetworkComms component.
- VOID	Return

	Initialise
Sets up the GSM module. Returns 0 for OK, 255 for no reply and 254 for command fail.
- BYTE	Return

	Left
Rotates the robot left - waits for the angle to be traversed before returning
- UINT	Angle
Angle to turn in degrees
- VOID	Return

	ReadIR
Reads an IR sensor 0=Left, 1=FrontLeft, 2=Front, 3=FrontRight, 4=Right, 5=RearRight, 6=Rear, 7=RearLeft
- BYTE	index
0=Left, 1=FrontLeft, 2=Front, 3=FrontRight, 4=Right, 5=RearRight, 6=Rear, 7=RearLeft
- UINT	Return

	LCDDrawPixel
Allows a single pixel on the LCD to be set or cleared
- BYTE	X
X Pixel 0-127
- BYTE	Y
Y Pixel 0-31
- BYTE	State
0=White (Off), 1=Black (On)
- VOID	Return

	ServoSetPosition
Allows one of the servo positions to be assigned
- BYTE	Channel
Range 0-3
- BYTE	Position
Range 0-255
- VOID	Return

	CardBitmap
Displays a monochrome bitmap read from the card on the LCD
- BYTE	X
Range 0-127
- BYTE	Y
Range 0-31
- STRING	Filename
- BYTE	Return

	CardRecordMic
Records an audio stream on the card from the microphone
- BYTE	BitDepth
0=8-bit, 1=16-bit
- BYTE	SampleRate
Sample Rate 0=8KHz, 1=16KHz
- UINT	RecordTime
Time to record for in seconds, Range 0-65535
- STRING	Filename
- BYTE	Return

	CardOpen
Attempts to open an existing file on the SD card 255=Error, 1=File not found, 0=Open OK
- STRING	Filename
- BYTE	Return

	Forwards
Drives the robot forwards - waits for the distance to be traversed before returning
- UINT	Distance
Distance in mm
- VOID	Return

	ReadBearing
Reads the compass bearing based on the degrees clockwise from magnetic north.
[[File:]] -	Return

	GetConsoleHandle
Gets the handle to the console allowing data displaying on the panel etc.
[[File:]] -	Return

	LCDDrawLine
Allows a single pixel width line to be drawn on the LCD
- BYTE	X1
X Pixel 0-127
- BYTE	Y1
Y Pixel 0-31
- BYTE	X2
X Pixel 0-127
- BYTE	Y2
Y Pixel 0-31
- VOID	Return

	ServoAutoMoveToPosition
Allows one of the servo positions to move gradually to a new position
- BYTE	Channel
Range 0-3
- BYTE	Position
Range 0-255
- VOID	Return

	ReadAllValue
Reads a single value stored from the read all command Index dictates which sensor value to read
- BYTE	Index
0=SW, 1-8=IR, 9-10=Line, 11=Light, 12=Mic, 13-15=Accel
- UINT	Return

	LCDBacklight
Allows the LCD backlight brighntess to be adjusted
- BYTE	Intensity
Range 0-100, 0=Off, 1=Min Brightness, 100=Max Brightness
- VOID	Return

	LCDDrawRect
Allows a rectangle to be drawn on the LCD
- BYTE	X1
X Pixel 0-127
- BYTE	Y1
Y Pixel 0-31
- BYTE	X2
X Pixel 0-127
- BYTE	Y2
Y Pixel 0-31
- VOID	Return

	ReadLine
Reads one of the IR line sensors 0-1 0=Left, 1=Right
- BYTE	index
0=Left, 1=Right
- UINT	Return

	ServoDisable
Allows one of the servo outputs 0-3 to be disabled
- BYTE	Channel
Range 0-3
- VOID	Return

	ServoEnable
Allows one of the servo outputs 0-3 to be enabled
- BYTE	Channel
Range 0-3
- VOID	Return

	CardReadByte
Reads a byte from the currently open file. Starts at the beginning of the file and auto increments to the end
- BYTE	Return

	CardErase
Attempts to delete an existing file on the SD card 255=Error, 1=File not found, 0=Delete OK
- STRING	Filename
- BYTE	Return

	CardWriteByte
Appends a byte to the end of the currently open file
- BYTE	Data
- VOID	Return

	EncoderRead
Reads one of the motor encoder counters. Approx 0.328296mm of travel per encoder unit.
- BYTE	index
0=Left, 1=Right
- UINT	Return

	SetMotors
Sets the motor speeds without feedback Range -100 to 100
[[File:]] -	Left
Range -100 to 100
[[File:]] -	Right
Range -100 to 100
- VOID	Return

	Backwards
Drives the robot backwards - waits for the distance to be traversed before returning
- UINT	Distance
Distance in mm
- VOID	Return

	EncoderReset
Resets the motor encoder counters
- VOID	Return

	LCDVerbose
Allows the LCD to automatically report the API commands as they get processed. Default - verbose on
- BYTE	State
0=Off 1=On
- VOID	Return

	SetProp
Allows the COM port property to be set from a parent component.
- STRING	PropName
- ULONG	PropVal
- VOID	Return

	CardInit
Attempts to startup the SD card 255=No Card, 254=Init Fail, 0=Init OK
- BYTE	Return

	GetProp
Allows the property filter for the COM port list to be copied to a parent component.
- STRING	PropName
- STRING	Return

	LCDClear
Clears the LCD
- VOID	Return

Property reference

	Properties
	Host
Address of MQTT Broker Can be an IP Address or URL (URL only supported by some hardware platforms)
	Port
Port used by MQTT Broker Default 1883 for unencrypted access and 8883 for encrypted access.
	Client identifier
Client identifier (Maximum length 20 characters) Must be unique to the broker.
	Network Timeout
Maximum time in mS to wait for network responses
	Read Timeout
Amount of time in ms to wait for incoming messages.
	Keep Alive
The Keep Alive is the maximum time interval that is permitted to elapse between the point at which the Client finishes transmitting one Control Packet and the point it starts sending the next, measured in seconds.
	Network Component
Pointer to the network communications component providing TCP simulation and abstraction for embedded TCP modules.
	Authentication
Selects if the broker is open or if the broker requires a username and password.
	Connections
	Simulations