What is TF6701？

In this tutorial I will explain how to use Beckhoff TF6701 to publish the message toBroker.

We can use this to connect to AWS,Google ,Azure also.

Manual

Please download the manual from the below link:

https://download.beckhoff.com/download/Document/automation/twincat3/TF6701_TC3_IoT_Communication_MQTT_EN.pdf

System Requirement

And also, you do not need any additional installation of TF6701.

Packages

This time, I will use TF6701 only.Let’s explain TF6720 in the future :)!。

Let me explain AWS IOT Core. It is a platform that comes from Amazon, we can use this platform to connect all our devices to the internet. In TwinCAT , we can use TF6701 to save our life and take the configuration to be easy.

Build the AWS IOT Core

Please reference the following post to get more information about how to build the AWS IOT Core platform.

Siemens#Using CC712 to Connect your S7-1500 to AWS IOT Core | (soup01.com)

Function Block

The FB_IotMqttClient Function block is used to connect to AWS Iot Core.

By using this Function block of tF6701, we can easily connect the Runtime variables to Local/Cloud MQTT Broker.

VAR_INPUT

sClientId	STRING(255)	Reference to the name of “Things” in AWS IOT Core.
sHostName	STRING(255)	The URL of Broker.Reference to the “EndPoint” of AWS IOT Core.
nHostPort	UINT	Default=1883. If TLS is used, please change to 8883.
sTopicPrefix	STRING(255)	The command that you want to insert automatically.
nKeepAlive	UINT	Watchdog Time（s）
sUserName	STRING(255)	Username while login to the Broker(Option)
sUserPassword	STRING(255)	Password while login to the Broker(Option)
stWill	ST_IotMqttWill	The message while connection is failed.
stTLS	ST_IotMqttTls	if TLS-secured connection is used, you need to set these parameters.
ipMessageFiFo	I_IotMqttMessageFiFo	FB_IotMqttMessageQueue instance

ST_IotMqttWill

You can set the Qos,Payload in this DUT.

sTopic	STRING(255)	Message Topic
pPayload	PVOID	The Memory address of the Payload
nPayloadSize	UDINT	The size of the Payload
eQoS	TcIotMqttQos	Qos(Quality of Service)
bRetain	BOOL	1=take sequence

ST_IotMqttTls

The DUT of TLS security settings.

You can useCA(certificate authority) or PSK(PreSharedKey) .

sCA	STRING(255)	The path of certificate authority (CA)
sCert	STRING(255)	The path of Client certificate
sKeyFile	STRING(255)	The path of Client Private Key Path
sKeyPwd	STRING(255)	The password of the Private Key
sCrl	STRING(255)	The path of certificate revocation list
sCiphers	STRING(255)
sVersion	STRING(80)	TLS version。‘tlsv1’・ ‘tlsv1.1’・‘tlsv1.2’・‘tlsv1.3’
bNoServerCertCheck	BOOL	Check the Server certification is valid or not
sPskIdentity	STRING(255)	TLS PSK PreSharedKey identity
aPskKey	ARRAY[1..64] OF BYTE	TLS PSK Psk Key
nPskKeyLen	USINT	The size of Psk key
sAzureSas	STRING(511)	Only used in Microsoft Azure IoT Hub

VAR_OUTPUT

bError	BOOL	1=FB is error
hrErrorCode	PVOID	ErrorCode
eConnectionState	ETcIotMqttClientState	Current Status
bConnected	BOOL	Broker connection is established or not

Method

Execute

You need to call this Method cyclically .

VAR_INPUT

bConnect

BOOL

1=Connect to Broker

Publish

MQTT BrokerにPublish動作するMethodです。

VAR_IN

sTopic	STRING	The Pushlish Topic
pPayload	PVOID	The memory address of payload
nPayloadSize	UDINT	The size of the payload
eQoS	TcIotMqttQos	Qos
bRetain	BOOL
bQueue	BOOL	Spare

RETRUN

Publish

BOOL

1=Publish completed

Sorry I will explain it in my next post.

Unsubscribe

Sorry I will explain it in my next post.

VAR_INPUT

sTopic

STRING

The topic that you want to Unsubscription

Return

Unsubscribe

BOOL

1=Unsubscribe is completed.

ActivateExponentialBackoff

Method for backoff.Not used in this post.

DeactivateExponentialBackoff

Method for backoff.Not used in this post.

Implemention

Now I will explain how to implement it,

Insert Library

References>Add library.]

Search Tc3_IotBase and Import it.

And also import the Tc2_Utilities library.

Program

Now is the time to create the program.The flow is very simple – set all the connection parameters(certificate,Private Key,Endpoint, port and Client id), then call the Function Block to establish a connection to AWS IOT CORE. Finally publish the message.

VAR

VAR
MqttClient :FB_IotMqttClient;
bPublish :BOOL:=FALSE;
sTopicEmail :STRING(255) := ‘TwinCAT/TF6701/Devices1’;
bSend :BOOL;
sPayloadEmail :STRING(255) := ‘{“default”: “Hello from TwinCAT”,”message”: “Hello from TwinCAT”}’;
bConnect :BOOL;
bsetPars :BOOL;
icoun :INT;
MessageQueue :FB_IotMqttMessageQueue;

END_VAR

MAIN

MqttClient.nHostPortis the Endpoint URL ofAWS IOT Core.

MqttClient.nHostPort – we care usingMQTT TLS Secure,please set it to 8883.

MqttClient.sClientId – the Name of your “Things” inAWS IOT Core.

sCert and sKeyFileis are the files that you download while ”Things” is created.

IF bsetPars THEN
MqttClient.stTLS.sCA:=’c:\Cert\aws\AmazonRootCA1.pem’;
MqttClient.stTLS.sCert:=’c:\Cert\aws\ccf8d8b84f-certificate.pem.crt’;
MqttClient.stTLS.sKeyFile:=’c:\Cert\aws\ccf8d8b84f-private.pem.key’;
MqttClient.sHostName:=’a30hlb7uyo754j-ats.iot.us-east-2.amazonaws.com’;
MqttClient.nHostPort:=8883;
MqttClient.sClientId:=’mythings’;
MqttClient.ipMessageQueue:=MessageQueue;
MqttClient.sTopicPrefix:= ”;
END_IF;

MqttClient.Execute(bConnect:=bConnect);
IF MqttClient.bConnected THEN
icoun:=icoun+1;

END_IF

IF bPublish THEN
MqttClient.Publish(
sTopic:= sTopicEmail
,pPayload:= ADR(sPayloadEmail)
,nPayloadSize:=LEN2(ADR(sPayloadEmail))
,eQoS:= TcIotMqttQos.AtMostOnceDelivery
,bRetain:= FALSE
,bQueue:= FALSE);
bPublish:=False;
END_IF