4.Embedded programming

This week I have started programming.I've been practicing with two programming languages: Python and C++.

Group Task:

Group task

My first steps in programming

I will start first with Python because I have been told it is more intuitive for beginners. The first thing I did was to understand variables, functions, conditionals and loops. I did some exercises in Python in general to then move on to MicroPython and C++ .

I used two programs. The first was a web page called mBlock to understand the logic through blocks and images.The second was programming in visual studio code.

Study of Circuits and Microcontroller Components

To start programming I used the Wokwi simulator.

Then, I started analizing at some circuits with the microcontroller and the function of each component inside the circuit.

To understand these things, I started with MicroPython. Here I had to choose which microcontroller to use for my simulation.

Definition of microcontroller:

A microcontroller unit (MCU) is essentially a small computer on a single chip. It is designed to handle specific tasks within an embedded system without the need for a complex operating system.

I explored some microcontrollers and found the ESP32 microcontroller for its features.

ESP32 DevKit V4 Hardware Specifications

• Microcontroller: ESP32-WROOM-32D with dual-core processor at 240 MHz.
• Memory: 4 MB flash memory and 520 KB SRAM.
• Wireless Connectivity: Wi-Fi 802.11 b/g/n/e/i, Bluetooth v4.2 BR/EDR and BLE.
• I/O Interfaces: 36 GPIO pins (including analog input and PWM pins), UART, SPI, I2C, I2S, ADC, and DAC.
• Power Supply: 5V input via micro-USB connector or 3.3V via GPIO pins.
• LEDs: Power indicator LED.
• Antenna: Integrated PCB antenna.
• MicroSD Card Slot: Supports cards up to 4 GB.
• Dimensions: 53 mm x 28.5 mm x 14.2 mm.
• programmable in: C++, MicroPython, CircuitPython, ESP-IDF, JavaScript (Espruino), Lua (NodeMCU), Rust, and TinyGo.

To understand the pins, I imagined that the ESP32 was a robot and the pins were the arms of the robot. Each leg has a different function. For example: GPIO pins are like normal legs; they can activate LEDs and receive information. GND is the return path; it is called “ground”. ADC helps with things like controlling light brightness and is useful for light and temperature sensors. DAC can apply force to a variable, for example, to increase brightness or volume slowly.2 And so on with the other pins.

• Download Esp32 datasheet

MicroPython

Now, for the code, I started with MicroPython.

First, I began with basic tasks, like turning on a light with a button. a Then, I used a PIR sensor for my final project and turned on the lights with this sensor.

Concept	Description
Variables	Store data (integers, floats, strings) for use in the program.
Pins	Digital or analog input/output pins used for hardware interaction.
Functions	Blocks of code that perform a specific task, defined using def.
Control Structures	Control the program flow, such as if, for, while.
Libraries	Pre-written code to interact with hardware, like machine for GPIO.
UART	Used for serial communication between devices.
Timers	Used to run functions periodically with the Timer class.
Interrupts	Allows response to specific events (e.g., button presses) without polling.
I2C and SPI	Protocols for communication with sensors and devices (machine.I2C or machine.SPI).
Exceptions	Handles errors using try, except blocks.

(This table was created by ChatGPT). Promt: “Give me a short table of MicroPython concepts”.

1. First, I import the library to control the pins with these functions: from machine import Pin: Then, I configure my pins with their locations, like LEDs on the microcontroller.
2. I configured everything as output pins and also configured the sensor: sensor = Pin(26, [Pin.IN])
3. Then, I added a condition that says that as long as the sensor detects motion (value 1), the LEDs will have a value of 1, and the console will print the sentence “A motion was detected”.
Otherwise, if the sensor does not detect motion (value 0), the LEDs will have a value of 0.
4. I added the function time.sleep(), which pauses the program to allow the LEDs to turn on.

Code in Micropython

			    
from machine import Pin

sensor = Pin(26, Pin.IN)

#location of the LEDs on the microcontroller
led1 = Pin(15, Pin.OUT)
led2 = Pin(2, Pin.OUT)
led3 = Pin(4, Pin.OUT)

print("If it detects movement, the LEDs will turn on")
#Location of the sensor
sensor = Pin(26, Pin.IN)


while True:
  if sensor.value() == 1:

    led1.value(1)
    led2.value(1)
    led3.value(1)
    print("a movement was detected")

  else:
    led1.value(0)
    led2.value(0)
    led3.value(0)
time.sleep(0.5)

This is my video in Wokwi with microphyton with MQTT connection, but later I will explain how I did it.

simulation in wokwi

Programming in C++ (Arduino)

Next, I tried the same thing in C++.

First, here is a table with the most important concepts in Arduino C++:

Concept	Description
Variables	Store data (integers, floats, strings) for use in the program.
Pins	Digital or analog input/output pins on the Arduino board.
Functions	Blocks of code that perform a specific task, such as setup() and loop().
Control Structures	Control the program flow, such as if, for, while.
Libraries	Pre-written code that adds functionality, such as controlling sensors or motors.
Serial Communication	Allows sending and receiving data between Arduino and a computer using Serial.begin().
Analog vs Digital	Analog signals (continuous values) and digital signals (high/low).
I/O Functions	Interacts with pins, such as pinMode(), digitalWrite(), digitalRead().
Delays	Pause the program execution, e.g., delay(1000) for 1 second.

(This table was created by ChatGPT). Promt: “Give me a short table of Arduino C++ concepts”.

I began with basic tasks, like turning on lights following a sequence.


1. First I start defining my pins.
2. Then I set void setup() is used to do the initialization tasks. Serial.begin()is to start the serial communication between the microcontroller and a computer. Serial.println is to print a message to the "Serial Monitor".
3. Then configure the sensor pin as input and the light pins as output.
4. I used the void loop() function that keeps the program running continuously. To set the conditional, I put if the pir status is high, the light is also high and they turn on but if the pir status is low, the light is also low.
5. To print the messages I use the Serial.println() function.

simulation in wokwi

Code in Arduino C++

#define PIR_PIN 12
#define Led1 18
#define Led2 5
#define Led3 17


void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
  pinMode(PIR_PIN, INPUT);
  pinMode(Led1, OUTPUT);
  pinMode(Led2, OUTPUT);
  pinMode(Led3, OUTPUT);

  
}

void loop() {
  // put your main code here, to run repeatedly:
  int estadoPIR = digitalRead(PIR_PIN);
  delay(10);

  if (estadoPIR == HIGH) {  // if there are movements
        digitalWrite(Led1, HIGH);
        digitalWrite(Led2, HIGH);
        digitalWrite(Led3, HIGH);
        Serial.println("Motion detected! LEDs on.");
  } else {                 // if there aren't movements
        digitalWrite(Led1, LOW);
        digitalWrite(Led2, LOW);
        digitalWrite(Led3, LOW);
        Serial.println("No movement. LEDs off.");
  }
  
}

Comunication with internet

To create a communication, I decided to use the wireless connection, in this case the Internet. I used MQTT to send messages with the sensor and saw an example of a temperature sensor.

Example extracted from Wokwi

I tried to do the same with my PIR sensor.

1. First, I had to understand some basic concepts:
• What is MQTT? MQTT (Message Queuing Telemetry Transport) is a messaging protocol that allows devices to communicate over bandwidth-limited networks. It is a key part of the Internet of Things (IoT) and is used in many applications, including smart devices and industrial automation.

• from umqtt.simple import MQTTClient This imports the MQTT client library to connect to an MQTT broker.

These lines set the connection parameters for the MQTT client:

• MQTT_CLIENT_ID: Sets a unique identifier for the MQTT client.
• MQTT_BROKER: Defines the address of the MQTT server to connect to.
• MQTT_USER: Defines the user name for the MQTT connection (empty if not required).
• MQTT_PASSWORD: Defines the password for the MQTT connection (empty if not required).
• MQTT_TOPIC: Defines the topic for sending or receiving messages.
• To connect to the internet in Python, I have to set the pin of the sensor that MQTT is going to read.
2. Next, I print the Internet connection messages, and it is important to use end=“” to print a message without going to the next line.
• network.WLAN(network.STA_IF): This prepares the chip to use Wi-Fi in client mode (STA_IF).
• sta_if.active(True): This activates the Wi-Fi interface to start scanning for networks.
3. Then, I set the Wi-Fi network in this case to the simulator:
• sta_if.connect('Wokwi-GUEST', '').
4. When connected, the print statement sends “connected” to the console.

MQTT conection program with Pir sensor

import network
import time
from machine import Pin
from umqtt.simple import MQTTClient

# MQTT Server Parameters
MQTT_CLIENT_ID = "micropython-movment-demo"
MQTT_BROKER    = "broker.mqttdashboard.com" 
MQTT_USER      = ""
MQTT_PASSWORD  = ""
MQTT_TOPIC     = "wokwi-movement"

sensor = Pin(26, Pin.IN)
print("Connecting to WiFi", end="")
sta_if = network.WLAN(network.STA_IF)
sta_if.active(True)
sta_if.connect('Wokwi-GUEST', '')
while not sta_if.isconnected():
  print(".", end="")
  time.sleep(0.1)
print(" Connected!")

print("Connecting to MQTT server... ", end="")
client = MQTTClient(MQTT_CLIENT_ID, MQTT_BROKER, user=MQTT_USER, password=MQTT_PASSWORD)
client.connect()

print("Connected!")
#location of the LEDs on the microcontroller
led1 = Pin(15, Pin.OUT)
led2 = Pin(2, Pin.OUT)
led3 = Pin(4, Pin.OUT)

print("If it detects movement, the LEDs will turn on")
#Location of the sensor
sensor = Pin(26, Pin.IN)


while True:
  if sensor.value() == 1:

    led1.value(1)
    led2.value(1)
    led3.value(1)
    print("a movement was detected")
    client.publish(MQTT_TOPIC, "Detected movement")

  else:
    led1.value(0)
    led2.value(0)
    led3.value(0)
time.sleep(0.5)

simulation in wokwi

Conclusion

This week has been a challenge because I had to research how each function of each component works in order to program, and then I had to learn how to program in two languages I didn't know. Although I have only programmed basic things, Now i understand how to do it. Between the two languages: MicroPython and Arduino C++, I prefer MicroPython because it is very intuitive, but I would also like to continue with Arduino C++. In the case of this, although it has been a bit more difficult because its syntax is more structured. I would like to continue learning how to optimize code in Arduino and better understand the handling of libraries and control structures. I liked this week because I learned things I didn't understand before and I think I'm progressing well.