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Artículo Científico / Scientific Paper |
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https://doi.org/10.17163/ings.n28.2022.05 |
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pISSN: 1390-650X / eISSN: 1390-860X |
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PLATFORM FOR DISTANCE LEARNING OF MICROCONTROLLERS
AND INTERNET OF THINGS |
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PLATAFORMA DE ENSEÑANZA A DISTANCIA DE MICROCONTROLADORES E INTERNET DE LAS COSAS |
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Renata Pereira1,* |
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Received: 06-06-2022, Received after review:
14-06-2022, Accepted: 21-06-2022, Published: 01-07-2022 |
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Abstract |
Resumen |
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Due to the increasing technological
development in embedded systems and the Internet of Things (IoT), devices based on microcontrollers are increasingly
applied in various areas of knowledge. In this context, online educational
platforms and products are considered virtual remote laboratories because
students can access the physical devices anywhere as long as they have an
Internet-connected computer system. In this sense, this work describes the
design and development of a platform with four online educational products
for teaching microcontrollers and IoT. These
educational products are based on open-source software, allowing their free
online distribution and can be accessed from a cloud server. The open-source
and multiplatform (Linux, Windows®, and Mac OSX) approach allows more
significant user interaction and accessibility. The online educational
products make possible the programming of ESP32 firmware remotely via OTA
(over the air) and Linux embedded systems based on Raspberry Pi (Rpi), enabling virtual microcontroller laboratory
applications. In addition, online educational products allow the manipulation
of GPIO pins via the Internet through a graphical interface of the ESP32 and
ESP8266 microcontrollers and the Rpi. In this
context, the proposed online platform, running on a cloud server, was tested,
and the four online educational products of distance learning and actual
application of microcontrollers and the Internet of Things have been
validated and worked as designed. |
Debido al creciente desarrollo tecnológico de los sistemas embebidos y el internet de las cosas (IoT), los dispositivos basados en microcontroladores se aplican cada vez más en diversas áreas del conocimiento. En este contexto, las plataformas y productos educativos online se consideran laboratorios virtuales remotos, ya que los estudiantes pueden acceder a los dispositivos físicos en cualquier lugar siempre que dispongan de un sistema informático conectado a internet. En este sentido, este trabajo describe el diseño y desarrollo de una plataforma con cuatro productos educativos online para la enseñanza de microcontroladores y IoT. Estos productos educativos están basados en software de código abierto, lo que permite su distribución gratuita en línea y se puede acceder a ellos desde un servidor en la nube. El enfoque de código abierto y multiplataforma (Linux, Windows® y Mac OSX) permite una mayor interacción y accesibilidad del usuario. Los productos educativos en línea hacen posible la programación del firmware de ESP32 de forma remota a través de OTA (over the air) y de sistemas embebidos Linux basados en Raspberry Pi (Rpi). Además, los productos educativos en línea permiten manipular los pines a través de la interfaz gráfica de los microcontroladores ESP32 y ESP8266, así como del Rpi. Como resultado, se prueba la plataforma en línea propuesta, ejecutada en un servidor en la nube, y se validaron los cuatro productos educativos de aprendizaje a distancia y la aplicación real de microcontroladores e IoT se encuentran operativos tal como fueron diseñados. |
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Keywords: platform, distance learning, microcontroller,
Internet of things, embedded systems, virtual laboratory |
Palabras clave: plataforma, educación a distancia, microcontrolador, internet de las cosas, sistemas embebidos, laboraorio virtual |
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1,* Electronics, Federal
Institute of Alagoas, Alagoas, Brazil. Corresponding author ✉: renata.pereira@ifal.edu.br 2 Electrical
Engineering, Federal University of Paraíba, Paraíba, Brazil. 3 Electrical Engineering, Universidad de Guayaquil, Guayaquil, Ecuador. 4 Electrical Engineering, Universidad Politécnica Salesiana, Guayaquil, Ecuador. Suggested citation: Pereira, R.; De Souza, C.; Patino, D. and Lata, J. “Platform for Distance Learning of Microcontrollers and Internet of Things”. Ingenius, Revista de Ciencia y Tecnología. N.◦ 28, (july-december). pp. 53-62. 2022. doi: https://doi.org/10.17163/ings.n28.2022.05.
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1.
Introduction The COVID-19 pandemic demonstrated
that the teaching-learning process in educational institutions was hampered
by the lack of and need for face-to-face classes. Several strategies are
implemented for schools and universities to reduce the negative impact on
students’ learning and continuity of education [1,2]. Adopting distance
practices has become a crucial part of teaching, especially in Engineering,
Science, and Technology courses [3]. Thus, this paper describes a didactic
tool that allows the implementation of online practices of microcontrollers
and the Internet of things. Due to the
increasing technological development in the areas of embedded systems and the
Internet of things (IoT), microcontroller-based
devices are increasingly applied in various areas of knowledge such as motor
control, security systems, elevator control systems [4], power generation
monitoring [5] and in applied scientific research [6]. Therefore, teaching
embedded systems, microcontrollers, and IoT topics
becomes more and more relevant in Science and Engineering courses. Since
online educational products based on microcontrollers and IoT
are used over the Internet, remote teaching practices of these teaching
resources are possible. In this way, online educational platforms and
products are considered remote laboratories since students can access
physical devices from anywhere as long as they have a computer system with
Internet access [7, 8]. 1.1. Related Works The single-board computer, called
Raspberry Pi (Rpi), used in the distance education
teaching platform proposed in this work, was developed by the Raspberry Pi
Foundation to help children and adults learn in the computational area. It is
a low-cost portable computer based on free software and interfaces for
various peripherals. Other features are 1 GB RAM shared with a GPU (Graphics
Processing Unit), VideoCore IV 3D graphics core, 40
general-purpose input/output (GPIO) pins, four ports with USB 2.0 interface
for connecting keyboard and mouse used in desktop computers, HDMI (High
Definition Multimedia Interface) port, Ethernet port with RJ-45 interface, 56
micro SD (Secure Digital) card interface, camera and monitor interface, as
well as 5V power supply and audio output [9]. For developing
online educational products based on RPi, a set of
libraries and packages are used to ensure communication between all system
components. Then, to access Rpi, SSH (Secure Shell)
and VNC (Virtual Network Computing) protocols are tested to allow console and
graphical environment access, respectively. SSH is a protocol that enables
secure communication between two systems using a client/server architecture and
allows users to connect to a remote host. Unlike other |
remote protocols such as FTP (File
Transfer Protocol) or Telnet, SSH encrypts the login session, making it
virtually impossible for intruders to collect unencrypted passwords [10]. To ensure interconnection
between computers running Microsoft Windows and Linux operating systems and
to share files and folders, the Samba package, an open-source implementation
of the SMB (Server Message Block) protocol, was installed and configured
[11]. For Rpi’s C language programs, the WiringPi
C library was used, which can be used to program and configure the GPIO pins
[12]. Thus, to compile language programs written in C, the GCC (GNU Compiler
Collection) compiler is used, accessible, integrated distribution of compilers
for programming languages such as C, C++, C#, and Java [13]. The CURL library
was also used as an open-source command-line tool for URL syntax construction
and data transfer to the cloud [14]. The ESP32 IoT microcontroller was released by the Chinese company Espressif Systems, a manufacturer of embedded wifi antennas and IoT modules
with free software and hardware [15]. ESP32 is a low-power, dual-core,
dual-mode 32-bit wifi/Bluetooth microcontroller
(MCU). The ESP32 MCU has a frequency of 240 MHz and a processing power of 600
DMIPS (Dhrystone million instructions per second). On the other hand,
compared to the latest model, the 32-bit ESP8266 NodeMCU
IoT microcontroller with wifi
antenna is an earlier and more simplified version, also released by Espressif [16]. The PIC
microcontroller (PIC - Peripheral Interface Controller) is an integrated
circuit that contains all the circuitry necessary to realize a complete
programmable digital system in a single device. This teaching platform also
uses the 8-bit PIC18F2550 microcontroller produced by Microchip Technology.
The analogto-digital converter (ADC) module of the
PIC18F2550 has ten inputs and is capable of measuring the analog voltage on
each channel and converting the measured voltage into a 10-bit digital value
[17]. In this context, IoT technology enables the
communication between devices without human intervention [18, 19] and
understands that each device is an autonomous device connected to the
Internet. Such devices can interact and communicate automatically, maximizing
modularization, comfort, convenience, security, and energy savings, [20]. A
database is typically used to store data in the cloud to implement IoT systems. For this purpose, Cloud Computing provides
access to a shared pool of configurable computing resources, such as
non-relational databases, without needing in-depth knowledge of management
technologies [21, 22]. The cloud model simplifies the installation,
operation, and maintenance of information systems, increasing system
efficiency and reliability and reducing costs. |
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Cloud systems can be classified
according to the development or service model. Cloud development models are:
public, private, community, or hybrid; Cloud service models are: Platform as
a Service (PaaS), software as a Service (SaaS), or Infrastructure as a
Service (IaaS). In this work, PaaS is used, which consists of the use of
tools and resources to provide services to end-users who are students. Since
end-users share information on the same server in the cloud, data privacy and
confidentiality are the primary concerns. Thus, the educational products of
the learning platform make it possible for the stored data to be secure and
encrypted, allowing only the student owner to manage it. Thus, to write and
read variable data in the cloud, the proposed distance learning platform uses
Firebase Realtime Database, which is a NoSQL
database, i.e., it does not have as standard the system of tables and
relationships between data and where data are stored as JSON objects, [23].
In addition, the online didactic platform for distance learning of
microcontrollers allows real-time remote use by multiple users. 2.
Materials and
methods 2.1. Problem and Methodology IoT devices increasingly require
rapid intervention to update libraries and functionality and maintain the
security of online environments. To this end, quickly updating the firmware
of these IoT devices is an effective way to ensure
data security. Thus, the proposed distance learning instructional platform
uses IoT firmware updates via Over-The-Air (OTA).
The OTA firmware update is performed via HTTP, which allows downloading a
binary file from a cloud server to update the firmware of the
microcontrollers remotely. OTA update over the Internet is typically
implemented in two ways: (i) If a newer firmware
version is available, the device periodically queries the server containing
the compiled binary file (pull) or another online activation service, such as
Firebase. ii) the device receives a notification of a new firmware version
via the cloud (push), e.g., via MQTT, and performs the update. The server
stores the latest firmware version in binary, and then the time-varying URL
of the binary file, which is more secure and flexible than a predefined fixed
address, is sent to the microcontroller for download [24]. In this topic, the
online educational products of the microcontroller and Internet of things
distance learning didactic platform are presented. 3.
Results and
discussion The paper demonstrates an
educational product to update ESP32 and ESP266 microcontroller codes with the
same generic firmware using |
p://sanusb.org/espupdate. The free
version of Firebase (Google’s JSON object database) has been implemented to
generate an asynchronous update trigger in the cloud for .bin files, as illustrated
in Figure 1.
Figure
1.
Illustration of the operation of the Espupdate
environment The update (OTA)
transmits the compiled binary .bin files to a remote computer over the
Internet, enabling microcontroller virtual lab applications. To perform this
firmware update in the cloud, users must type in the firmware only the SSID,
password, and the same name as the profile entered on the website
http://sanusb.org/espupdate and by uploading the .bin to the website, the
firmware of the ESP microcontrollers is updated remotely over the Internet.
The user profile name entered at sanusb.org/spupdate
can be alphanumeric. It is possible to
test this webcast educational product on different networks by accessing the
website http://sanusb.org/espupdate/ through the lab or home network and the
ESP32 or ESP8266 microcontroller attached to the smartphone connected to the
4G mobile network, or vice versa. It is worth
considering that, through tests performed, .bin files compiled with the same
name and sequential downloads for the update in the cloud, it may happen that
the last .bin file sent for the update is not downloaded by the ESP
microcontroller but a previously uploaded .bin File, since they have the same
name and download URL. For this reason, in this project, the name of the .bin
files uploaded to the site have names based on the time of upload,
consequently, the download URL as well; this prevents a previously uploaded
file or another file with the same name from being downloaded, generating a
unique and unmatched URL. In this case, for the version of the .bin file name
and download URL, the following are used: year, month, day, time, and the
cyclic order of upload [25]. Once the .bin file update is completed and the microcontroller automatically restarts, the new verification code is sent to http://sanusb.org/espupdate/*Profile*/ to confirm the update on the website. It is important to note that |
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to use EspUpdate,
it is not necessary to open ports on the router or enable firewall
permissions. 3.1. ESPGpio Educational Product The educational product, called ESPGpio, allows changing the logic level of the ESP32 and
ESP266 microcontroller pins that can be programmed with open source firmware
[26], illustrated in Figure 2 through the graphical access available at
sanusb.org/esp. The user profile name entered at sanusb.org/espgpio can be alphanumeric.
Figure 2. Illustration of ESP32 and ESP8266 GPIO pins Figure 3 shows an
illustration of the automatic operation of the ESPGPIO environment. In this
case, a firebase cell is used to share between the microcontroller and the
user’s graphical environment. An even integer is represented by the sum of 2.
It is raised to the power of the number of activated pins.
Figure 3. Illustration of the GPIO pins of an ESP32 or ESP8266 The graphical
environment generated at sanusb.org/espgpio,
illustrated in Figure 4, has 30 GPIO pins that the user must select to load
switching through relays or electronic devices such as LEDs. It is important
to note that if there is a power failure or voltage drop, the state of the
last pins when the voltage drop is restored returns to normal, as the state
of the pins is updated and queried in Firebase, which is a persistent
database. After completing the
change of the pin states, the new pin state is indicated with green color in
the graphical environment http://sanusb.org/espgpio/*Profile*/, if it is at a
high logic level, as illustrated in Figure 4, where *Profile* is the profile
given by the user. |
Figure
4.
Illustration of the graphical environment of the ESP32 and ESP8266 GPIO pins It is important to
note that it is recommended to avoid using Gpio pin
one on the ESP8266 Nodemcu, which is the Tx pin, as it prevents serial communication of program
debugging by the serial monitor, and Gpio pins 06
to 11 on the ESP32 Devkit, as they are used for
flash recording. 3.2. Educational product RPI GPIO The educational product RPI GPIO
is similar to ESPGpio but is used to change the
state of the logic pins on the Raspberry Pi board. Figure 5 shows the
illustration of the staples of a RaspberryPi.
Figure 5. Illustration of the GPIO pins of a Raspberry Pi After creating the
profile at sanusb.org/gpio, a page is generated
with links to pages to access the Rpi pins and
firmware buttons for the extraction application and the insertion application
in bash Shell language, as illustrated in Figure 6. |
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Figure 6. Link to pages with pin buttons and programs for Rpi For both the
complete application and the push application, it is necessary, after
downloading the programs, to grant permission in the terminal as superuser (sudo su) and execute permission with the commands chmod 755 SgpioInstall.sh, for the pull application and chmod 755 Sgpiopushmqtt .sh, for push application [27]. Clicking on the profile
link generates a page with buttons representing each of the I/O pins of a Rpi, as illustrated in Figure 7. In the pull case,
clicking on the button for a given physical pin sends a command to a file
contained in the online profile periodically queried by the Sgpiointall.sh
script that is operating on the Rpi. In the case of
push MQTT, clicking the button sends a publish command to the broker
mqtt.eclipse.org on the topic with the same name as the user’s profile; in
the case of the example, lease and downloads this command to the Rpi that is operating the Sgiopushmqtt.sh script with
subscription (subscribe) to the same topic.
Figure 7. Illustration of the graphical environment of
Raspberry Pi GPIO pins With the RPI GPIO
environment, it is possible to create an IoT
application using a laptop or smartphone to, for example, control the
activation of household appliances via the Internet, such as a fan via a
relay, as illustrated in Figure 8. In this case, a Raspberry Pi Zero, also
accessible via the Internet, is used. As can be seen, to use the sanusb.org/gpio environment, it is |
necessary to create a profile
initially. After completing the profile, a link is generated to access a page
with buttons, and each button corresponds to a pin of the Raspberry Pi IoT device [27].
Figure
8.
Illustration of a circuit for IoT operation of a
fan with Raspberry Pi 3.3. IOTUS educational product The educational product IOTUS (IoT update system) is a PaaS, i.e., a platform as a
service in which the user can create a profile and update scripts in C,
python, or shell language on the Rpi-based Linux
embedded system and also update the firmware in hexadecimal of the PIC family
microcontroller through the USB port of the RPI [28], as illustrated in
Figure 9. Thus, IOTUS consists
of three main parts, namely: 1) Raspberry Pi-based Linux embedded system
(ELS), 2) Analog-to-digital converter embedded system (ADCES), which uses a SanUSB microcontroller, based on a free software and
hardware tool with the PIC18Fxx5X family, including the native USB interface;
and 3) WEB page for automatic real-time update (upload) of scripts.
Figure 9. Remote firmware and script
upgrade ADCES consists of the open-source development tool SanUSB illustrated in Figure 9. SanUSB is composed of open-source software and hardware of the PIC18Fxx5x family with a native USB interface. This |
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free tool is
efficient in project development because removing the microcontroller to
update the firmware is unnecessary, unlike other development systems that
typically use specific recording hardware and require a wired connection. In
addition, the SanUSB tool is cross-platform, i.e.,
it can be used on Windows®, Mac OSX, and Linux, as well as being plug and
play, i.e., it is automatically recognized by the operating systems without
the need to install any driver [29]. Thus, this tool
allows the compilation, recording, and emulation of a program to be performed
quickly and efficiently by connecting the microcontroller to a computer
system via USB. Its application is an RPi. The ELS RPi-based computer system can directly implement
electronic designs, mainly due to its general-purpose input/output (I/O) pins
(GPIO) with support for digital sensors, actuators, and I2C and SPI protocols
to perform communications with peripherals [30]. The communication variety
allows the RPi to communicate with a broader range
of peripherals, and the Wiring Pi pin access library, written in C,
facilitates programming and configuring the GPIO pins through a command-line
utility "gpio." This work has two ways of
communication between ADCES and RPi: serial
communication and USB interface. To realize serial communication between a
PIC microcontroller and the RPi pins of the ELS,
the ground (GND), GPIO 14 (TX), and GPIO 15 (RX) pins are used. In this work,
the computer system used to register the PIC microcontroller (ADCES) is the RPi (ELS), whose connection pins for USB and serial
communication are shown in Figure 10.
Figure 10. Serial
connection between ADCES (SanUSB board) (a) and RPi (b) Therefore, a
graphical interface and recording software was developed to directly transfer
the embedded Linux system interface firmware to the ADCES PIC |
using the Human
Interface Device (HID) communication protocol through the USB port. The
proposed ADCES is an embedded RISC system and allows online firmware updates
from the cloud. Files can be uploaded remotely to update ADCES firmware (.
hex files) and update RPi scripts (.c, .py or .sh files). A physical
connection between pin 11 of the RPi and pin 1 of
the ADCES is required to update ADCES. The PaaS profiles (PaaS A, B, or N)
illustrated in Figure 11 are free and automatically generated by the online
server after registering the user profile, where it is possible to debug
and/or test an IoT application. Thus, any user (A,
B, or N) can create and configure an IoT profile in
the cloud in real-time and update firmware and scripts over the Internet.
Figure 11. Proposed PaaS profile of IOTUS Accessing the web
page at http://sanusb.org/iotus/sanusb.php, illustrated in Figure 12, allows
sending and updating scripts in ELS with language extensions in C (.c),
Python (.py), Shell scripts (.sh),
and hexadecimal (.hex) in ADCES through the server.
Due to network latency, the address of the files uploaded to ELS and ADCES
are variable and are renamed with the user’s profile along with the updated
version, which starts with "0" and at each upload is incremented.
Considering the shape "ingenious," if the first file is Python, it
will be automatically renamed to "ingenius0.py" and
"ingenius1.py" will be the name of the script and, consequently, of
the new URL that is used to download by ELS.
Figure 12. IoT
scripts update the WEB page |
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IOTUS has been programmed to
upload files to the server through the http://sanusb.org/iot/sanusb.php page
by following these steps: 1. Insertion of the profile used by the student and
by ELS to download the file; 2. Browse for the firmware (.c, .py, .sh or .
hex) that will be sent for automatic update. Sample scripts are downloaded
from sanusb.org/iotus/examples.zip. 3. The ’Submit’
button executes the file transfer to the server, which is then renamed and
automatically transferred to the ELS. IOTUS is programmed to operate
decentralized and distributed, allowing multiple users and multiple
simultaneous communications using the same cloud server. After entering a
profile name and submitting any firmware, as illustrated in Figure 13,
SloaderInstall.sh is automatically generated and available for download.
Figure 13. The website with
a link to download the Sload-erInstall.sh script Therefore, to update
the firmware (.c, .py, .sh,
or .hex) via the cloud, it is necessary to
previously run the SloaderInstall.sh script in ELS to check for new firmware
updates at user-defined time intervals, download the updated firmware and
perform a specific task according to the file extension. The SloaderInstall.sh
script checks at startup whether the libraries required for this educational
product are installed and, if not, install them in Rpi.
If a "hexadecimal" file is sent, ELS writes the file to ADCES over
the cable connection between RPi pin 11 and ADCES
pin 1. If a ".c" file is sent, ELS compiles the script and then
executes the compiled file. In the case of a shell script or a file created
in Python, ELS directly runs the file in the background. Figure 14
illustrates the flowchart of the SloaderInstall.sh verification operation. Another feature of
the proposed IOTUS PaaS is that when using this online educational product,
there is no need to unblock router and/or firewall ports. As an application
for the developed IOTUS, a Photovoltaic (PV) module supplying a 50 W load is
used, with the following specifications: Model YL95P-17b 2/3, Maximum Power
95 WP, Efficiency 14.3%, open circuit voltage (Voc)
22.5 V and short circuit current (Isc) |
The sunshine hours
for Fortaleza, in Brazil, where the system was implemented, are from 6 am to
4 pm.
Figure 14. SloaderInstall.sh operation flowchart
Figure 15. PV Temperature on January
in Fortaleza-BR As a second
application, IOTUS ESP32 system is validated using a Programmable Logic
Controller (PLC) with 12-bit resolution AD channel [32]. Figure 16 shows the
monthly average curve of the PV module temperature measured. For temperature
values above 52 ºC, the error between the proposed IoT
monitoring using ESP32 and the PLC increases, about 2 ºC; for lower
temperature values, the measurement follows the reference value. Figure 17
shows the correlation between the PV module temperature measured by the
proposed IoT monitoring and PLC reference value for
the average measurements. Using the Root Mean Square Error (RMSE), the
correlation is about 0.9989. |
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Figure 16. PV module
temperature measured by the proposed IoT monitoring
and PLC
Figure 17. Correlation
between PV module temperature measured by the proposed IoT
monitoring and PLC reference value 4.
Conclusions This work described the design and
development of four educational products in an online platform for distance
learning of microcontrollers and IoT, which were
tested, validated, and worked as designed. Specifically, the proposed ESP
UPDATE educational product allows the update of the ESP32 and ESP266
microcontroller codes in the cloud, and it is possible to use it through the
Internet anywhere and on any device (computer, smartphone), and this allows
virtual microcontroller lab applications. The educational product ESPGPIO for
ESP32 and ESP8266 and the RPI GPIO for Rpi allow IoT applications from a laptop or smartphone to control
the activation of home appliances through the Internet intuitively and
interactively. IOTUS enables online
recording of ADCES developed with a PIC microcontroller and firmware update
on a Raspberry Pi-based embedded Linux system (ELS). Using open-source and
cross-platform software (Linux, Windows®, and Mac OSX) for online teaching
allows for more significant user interaction and accessibility due to the
possibility of free distribution. Another advantage of the four proposed
educational products is that there is no need to unblock ports and/or
firewalls when using the cloud service. Finally, this paper
also presented the main features and advantages of the microcontrollers used
in the online platform: low cost and the use of accessible hardware and
software. The use of Rpi simplified the processing
and provided a portable size circuit using Linux as the operating system and
C as a programming language. |
The development of
programs for the various functionalities demonstrated the possibility of
building an effective and low-cost solution where the user can add
functionalities and configurations according to his needs. In addition, the
proposed educational products eliminate the need to install software on the
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