This example demonstrates how to communicate between a remote computer and a micro-controller board located at different geographical locations through IoT MQTT protocol. Both devices shall be connected to the internet. ESP8266 WiFi module is used for connecting the micro-controller board to the internet through a local WiFi router. Analog and digital signals are acquired from the target board and send them to the remote computer where the signals are monitored (plotted and displayed). Some onboard LEDs of the target board are also controlled from the remote computer through the same channel.
In this example the host PC (that is used to program the micro-controller board) is used as the remote computer for monitoring and control. User is encouraged to use any remote computer for monitoring & control and to experience the true potential of the IoT protocol
User has to have access to a MQTT broker for this example to work. This example uses a free online MQTT broker available at the time of testing this example. Same IP address may not work for the user. Some of the free online MQTT brokers available at the time of writing this article are: broker.emqx.io, mqtt.eclipseprojects.io, broker.hivemq.com and public.cloud.shiftr.io. User may try one of these domain names for experimenting.
Target
Aries v2.0 development board is used in this project. However, any supported micro-controller board can be used. ESP8266 WiFi module is used with the micro-controller board to enable wireless connectivity.
Pre-Requisites
- CASP software is installed on the host PC
- Vega Aries BSP is installed.
- The project files are located at CASP installed directory ‘CASP/support/examples/vega_aries_examples/iot/03_mqtt_server’. These are also available for download at this link.
Connection Diagram & Model
Connect the circuit as shown below. Connect any sensor to the ADC pin A0 of the target board for sensing.
Configuration
- MQTT client ID, publisher and subscriber tokens are already configured in the ‘GPIO MQTT Client’ block on both the device models. User may modify these settings if required.
- IP address of a MQTT broker can be obtained by pinging its domain name in the Windows command prompt of the host PC as shown in below figure.
- The IP address thus obtained (shown highlighted in the above figure) can be entered in the configuration parameters of the network blocks of the native and target models. Below figure shows a snap shot of ESP8266 block parameters in the target model. Similar settings shall be configured in the ‘Windows IP’ block of the native model.
Procedure
- Connect the peripherals as shown in above connection diagram and connect the target board to the host PC.
- Launch CASP and open the downloaded project.
- Open Home->Simulation->Setup Simulation Parameters menu item. Under TargetHW->General tabs set ‘Target Programmer Port’ parameter to the serial port to which the board is connected.
- Configure the network parameters of the ‘ESP8266 block’ as shown in above figure. Also, configure MQTT parameters of the ‘GPIO MQTT Client’ model as mentioned in above clauses.
- User may enable CASP debug mode from ‘Setup Simulation’ window if debugging is required as shown in below figure.
- Build the model and program the board by clicking on Run button.
- After programming is completed the board should automatically establish WiFi connection and should connect to the remote MQTT broker.
- A sample screen shot of the debug window with the target board successfully connected to the remote MQTT broker is shown below
Procedure to run the Native Model on the host PC
- After successfully establishing WiFi connection with the target, load the ‘native_model’ project. Configure the ‘Windows IP’ block parameters as shown in below figure
- Configure the MQTT parameters of the GPIO MQTT Client model as mentioned above.
- Run the model by clicking on the Run button. A simulation panel window should open and communicate with the MQTT broker. Below message window shows a typical successful MQTT connection
- Below is the screen shot of the simulation window, displaying the data received from the remote target board
