Week 04 – Embedded Programming

This week’s personal assignment was to read and understand the data sheet of a microcontroller as well as perform a simulation of the microcontroller in use.

Here’s also the link to our group assignment of this week.

What is embedded programming?

It is the development of software that runs on embedded systems-computing devices built into larger systems to perform dedicated tasks. Unlike general-purpose computers, embedded systems are optimized for specific functions.

Languages used in embedded programming

The languages used in embedded programming are c/cc++ and python.

Microcontrollers

A microcontroller unit (MCU) is essentially a small computer on a single chip. It is designed to manage specific tasks within an embedded system without requiring a complex operating system (Schnider & Smalley, n.d.).

I’ll be using Wokwi for this simulation, so before starting with the simulation we will learn how to use it. For this I’ll be using the RP2040 microcontroller.

You can know certain features with its name like this:

Before choosing any microcontroller, the first thing you can do is go through its datasheet, and see if it works for the type of project that you are developing. Some features you can take into account are these:

You can find the datasheet used here

FEATURE RP2040
SRAM 264 kB
Flash Memory Not internal; supports up to 16 MB
GPIO Pins 30 multifunction GPIO pins
Analog Inputs 4 ADC inputs (12-bit, up to 500 ksps)
Communication 2× UART, 2× SPI, 2× I²C, USB 1.1 Host/Device, Programmable I/O (PIO)
Languages C/C++, MicroPython (official SDK support)
Wireless Not included
How to use Wokwi?

Now, let’s run a small test using Wokwi for our simulation.

01. First, we need to open Wokwi.

02. Then, we need to select Raspberry Pi Pico MicroPython, as it is the microcontroller we will be using.

03. fter that, where it says “sketch.ino” in the code editor, you can start adding your code.

04. If you need another component, you can add it by pressing the Add button.

05. Finally, you can run the simulation by pressing the Play button

Final Project IMU Simulation

Now, let’s make a simulation related to my project.

After researching different microcontrollers for my project, one of my main options is the ESP32. I have not made the final decision yet, but I chose this microcontroller because it has integrated Wi-Fi and Bluetooth, offers high processing power, and is well suited for interactive projects.

You can find the datasheet used here

FEATURE ESP32 Why it matters
CPU Dual-core Xtensa LX6 up to 240 MHz High processing power for multitasking and real-time control
SRAM 520 kB on-chip SRAM Allows more complex programs and buffering
Flash Memory External flash (commonly 4 MB) Enough space for firmware and libraries
GPIO Pins Up to 34 programmable GPIOs Supports multiple sensors and actuators
Analog Inputs Up to 18 ADC channels (12-bit) Good for reading analog sensors
Wireless Wi-Fi 802.11 b/g/n + Bluetooth (Classic & BLE) Enables IoT connectivity without extra modules
Communication UART, SPI, I²C, I²S, CAN Flexible connection with peripherals
Low-Power Modes Light sleep, Deep sleep, Hibernation Important for battery-powered projects
Special Features Touch sensors, PWM, RTC, ULP coprocessor Useful for interactive and low-power designs
Languages C/C++, MicroPython, Arduino framework Flexible development ecosystem
Step by step IMU

Step 1: Select the ESP in Wokwi

First, open Wokwi and select the ESP option.

Step 2: Choose the ESP32

From the available boards, select the ESP32, which will be the microcontroller used in this project.

Step 3: Add the IMU sensor

This project requires an IMU, so we need to add one. Click the “+” button to open the components menu and search for the MPU6050 sensor.

Step 4: Connect the MPU6050 to the ESP32

Make the following connections:

  • imu1: VCC → esp: 3V3 — Powers the IMU.
  • imu1: GND → esp: GND — Shares common ground.
  • imu1: SDA → esp: GPIO21 — Sends motion data via I²C.
  • imu1: SCL → esp: GPIO22 — Provides the clock signal.

Step 5: Programming

With the hardware connected, we can proceed to implement the C++ code that appears after this section.

Step 6: "MPU6050" library

Don't forget to install the "MPU6050" library for it to run properly.

Step 7: Testing

  • Open the Serial Monitor (115200 baud).
  • Move the MPU6050.
  • Verify that the values change in real time.
  • If not, check wiring and I²C pins.

Video process

Here you can see all the steps altogether

C++ Code used 

        #include <Wire.h>
        #include <MPU6050.h>
        #include <BLEDevice.>
        #include <BLEServer.>
        #include <BLEUtils.>
        #include <BLE2902.>
          
          MPU6050 mpu;
          BLECharacteristic *pCharacteristic;
          bool deviceConnected = false;
          
          void setup() {
          Serial.begin(115200);
          Wire.begin(21, 22); // SDA, SCL
          
          // ----- MPU -----
          Serial.println("Inicializando MPU6050...");
          mpu.initialize();
          
          if (mpu.testConnection()) {
          Serial.println("MPU6050 conectado correctamente");
          } else {
          Serial.println("Error de conexión con MPU6050");
        }
        // ----- BLE -----
        BLEDevice::init("FajaPerritoBLE");
        BLEServer *pServer = BLEDevice::createServer();
        BLEService *pService = pServer->createService("1234");
        pCharacteristic = pService->createCharacteristic(
                      "5678",
                      BLECharacteristic::PROPERTY_NOTIFY
                    );
        pCharacteristic->addDescriptor(new BLE2902());
        pService->start();
        BLEAdvertising *pAdvertising = BLEDevice::getAdvertising();
        pAdvertising->start();
        Serial.println("BLE listo para conectar");
      }
      void loop() {
      int16_t ax, ay, az;
      int16_t gx, gy, gz;
      mpu.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
      long movimiento = abs(ax) + abs(ay) + abs(az - 16384);
       Serial.print("Movimiento: ");
      Serial.print(movimiento);
      // -------- ACTIVIDAD --------
      if (movimiento > 2000) {
      Serial.print(" | EN MOVIMIENTO");
    } else {
    Serial.print(" | QUIETO");
  }
   // -------- POSTURA --------
  Serial.print(" | Postura: ");

  String mensaje;

  if (az > 14000) {
    mensaje = "NORMAL";
    Serial.println("NORMAL (de pie)");
  } 
  else if (az > 6000) {
    mensaje = "INCLINADO";
    Serial.println("INCLINADO");
  } 
  else {
    mensaje = "ACOSTADO";
    Serial.println("ACOSTADO o CAIDA");
  }

  // ----- ENVIO BLE -----
  pCharacteristic->setValue(mensaje.c_str());
  pCharacteristic->notify();

  delay(500);
}