Lab Session 1: Intro to microcontrollers programming¶

Estimated time: 1.5h (1 session)

1. Working with real hardware¶

1.1. Prepare the Arduino IDE¶

Follow the installation steps described in this guide.

Install Arduino IDE: Download it from this link.
Install the M5Stack board family:

You need to copy/paste this text to download the board package
```
https://static-cdn.m5stack.com/resource/arduino/package_m5stack_index.json 
```
Once the board package address is set, you can install it from the boards manager.

Warning

Remember to install the version 2.1.4. If you try to install version 3.X you won't be able to do exercises of the lab sessions. We'll talk about the versions 2.X and 3.X later and how to migrate our code from one to another. For now, just use the 2.X version.

Danger

Once you've done this, if you open the Arduino IDE later, a message will pop up letting you know that there are updates available for some libraries and asking whether you want to install the updates or not. Don't update the libraries

Info

This process may take a few minutes.

Once installed, you can select M5Core2 from the board selection menu.
Install the Arduino libraries for M5Core2:

Warning

When you press Install, you'll see the list of dependencies. You MUST install all the dependencies too.

Info

This is a long process that may take several minutes. Be patient...

Tip

In case the list of dependencies is that large that you cannot see the Install All button, you can press the tab key Tab twice to put the cursor over the button and then press Enter to install all the dependencies.
Install the CP2104 driver (USB driver):

Download it from this link if you're using Windows, from this link if you're using MacOS, or from this other link if you're using Linux.

More info about USB driver installation here.

Now, when you connect the M5Core2 devide to the PC with the USB cable, you can select the port in the Arduino IDE.
Info
- In windows, the port is called COMX, where X is a number that can vary from time to time, e.g., COM5.
- In linux, the port is called "ttyUSBX" or "ttyACMX", where X is a number that can vary from time to time, e.g., ttyUSB2.
Compile and upload the hello_world.ino example from M5Core2 library:

You can press the Upload (in red) button to compile and load the program to the device. Note that the button on the left (Verify - in green) compiles the program but doesn't upload it to the device.
OPTIONAL (do it ONLY if you have finished all the exercises of the lab session): You can open other examples if you want to see the potential of M5Core2. You can try this one:

Additional resources

Here you can find more documentation about some of the basic functions of M5Core2.

Pinout and Important Notes Below is the M5Core2 pinout. The pins marked in red are the ones we will use in the exercises.

Warning

Some pins on the M5Core2 are preconfigured, so pay attention when connecting external components.
The ESP32 inside the M5Core2 has 3 serial ports:
- Serial1 is reserved for the display (do not use it).
- Serial0 can be configured (pins G3 – RXD0 and G1 – TXD0), but it is reserved for USB connection to the PC.
- Serial2 is free and can be configured (pins G13 – RXD2 and G14 – TXD2) as regular GPIO using pinMode().

1.2. Turn an LED ON and OFF¶

Connect an LED as follows:

Run the following program:

#include <M5Core2.h>
#define LED_PIN 14

void setup() {
  M5.begin(); // Initialize M5Core2
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, HIGH);
  delay(500);
  digitalWrite(LED_PIN, LOW);
  delay(500);
}

Question

What does the #define do?
What does the pinMode() function do?
What does the digitalWrite() function do?

Question

Note that you had to include the #include <M5Core2.h> and the M5.begin(); // Initialize M5Core Why did you have to do that? what are these instructions for?

1.3. Additional exercises¶

1.3.1. Blink at a certain frequency¶

Using the same circuit as in the previous exercise, write a script that Blinks the LED at a frequency of 10Hz.
Question
- For how long does the LED has to be ON or OFF in each cycle?

1.3.2. Blink and stop¶

Using the same circuit as in the previous exercise, write a script that Blinks the LED at a frequency of 2Hz and stops the blinking after 5 seconds.
Question
- How many times does the LED blink?
- What is the final state of the LED when the blink stops, does it remain ON or OFF?
Tip

You may need to use the for loop, or the if...else condition.

2. Working in Simulation¶

2.1. Microcontrollers simulation¶

Launch an example¶

Access the Wokwi simulation environment via this link.
Select the ESP32 template.

Warning

Open the ESP32 template from Starter Templates, not from ESP-IDF Templates. The former is based on the Arduino IDE while the latter is based on the ESP-IDF environment that will not be used in the course.
Simulate the example sketch:
```
void setup() {
// put your setup code here, to run once:
Serial.begin(115200);
Serial.println("Hello, ESP32!");
}

void loop() {
// put your main code here, to run repeatedly:
delay(10); // this speeds up the simulation
}
```
Warning

Here you are simulating the behavior of the system including the code, you are not compiling the code (i.e., we're not generating the machine-readable code that will be executed by a processor). But the code MUST be compliable (i.e., it will be verified to check that I would compile )
Info
- Note that the real-time factor at the top right corner should be as close as possible to 100%. This value is a simulation performance metric. The closer it gets to 100%, the better is the simulation. A value of 100% means the simulation is running in real-time. If the value drops, the times in the simulation are no longer reliable.
- Note the instruction delay(10); // this speeds up the simulation. Try to comment this line and see what happens. What if you put delay(1); or delay(5);?
Question
- What is the purpose of the setup() function?
- What is the purpose of the loop() function?
- What does the delay() function do?
- Why do we need to put the delay(10) inside the loop() function?

Add hardware components¶

First of all, check the diagram.json file . What information do you see there?
Connect an LED to GPIO 21 with a resistor, as shown in the diagram (rotate - R and flip - P components if necessary).
Question
- Check again the diagram.json. What happened? Can you change the color of the LED to green from this file?
- What do you think you can do with the Library Manager?

2.2. Turn an LED ON and OFF¶

Connect an LED as follows:

Run the following program:

#define LED_PIN 21
#define BUTTON_PIN 35

void setup() {
    pinMode(LED_PIN, OUTPUT);
    pinMode(BUTTON_PIN, INPUT_PULLUP);
}

void loop() {
    digitalWrite(LED_PIN, HIGH);
    delay(500);
    digitalWrite(LED_PIN, LOW);
    delay(500);
}

2.3. Control the LED state with a push button¶

Implement the circuit shown in the following diagram and simulate a program that:
- Turns the LED ON when the button is pressed.
- Turns the LED OFF when the button is not pressed.
Tip
- Use the function digitalRead() to get the status of the button.
- You may need to use the if...else condition.
Warning

When you place the button, don’t forget to deselect the bounce option to avoid bouncing issues.
Question
- What information is included in the diagram.json? Did it change with respect to the previous exercise?
- Can you do the exercise without using the if...else condition? How?

2.4. Additional exercises¶

2.4.1. Blink¶

Using the same circuit as in the previous exercise, write a script that Blinks the LED while the button is pushed.

Tip

You may need to use the millis() function.

2.4.2. Short press vs long press¶

Using the same circuit as in the previous exercise, write a script that does the following:
- Short press (< 500 ms): Toggle LED (if the LED is ON, turns it OFF, and viceversa).
- Long press (≥ 500 ms): Blink LED.
Tip

You may need to use the millis() function, and the if...else condition.