Tutorial for creating multi cpp file arduino project

normandunbar · October 4, 2020, 4:12pm

I’ve been working on this, on and off, for a while. Other things got in the way but it’s now done. This is a small (contrived) tutorial on how to make a multi-file Arduino Sketch into a proper C+ project. Enjoy.

The Arduino Sketch

The multi-file Arduino sketch I’m using for this brief(!) tutorial is made up of a number of different *.ino files. These are, somewhat contrived, but it’s a small example. The sketch is called Blink_multifile and the files are:

Blink_multifile.ino
loop.ino
setupPins.ino
flashLED.ino

The main file, Blink_multifile.ino is as simple as this:

void setup() {
  setupPins();
  flashLED(4, 125);
}

As you can see, there’s nothing here except the setup() function which calls out to the other functions required to do all the setting up for the sketch.

The loop() function is found in loop.ino surprisingly enough, which looks like this:

void loop() {
    flashLED(1, 1000);
}

As you can see, there’s not much going on here either. The loop function calls out to yet another function, flashLED() passing two parameters. The flashLED() function lives in flashLED.ino which has the following code in it:

void flashLED(byte flashCount, int delayMS) {
    if (!flashCount) 
        return;

    for (byte x = 0; x < flashCount; x++) {
        digitalWrite(LED_BUILTIN, HIGH);
        delay(delayMS);
        digitalWrite(LED_BUILTIN, LOW);
        delay(delayMS);
    }
}

That’s looking better, we can see that the first parameter is the number of times a flash is required, while the second is the delay, in microseconds, between flashes. All that’s left now is the setupPins() function which lives in setupPins.ino:

void setupPins() {
    pinMode(LED_BUILTIN, OUTPUT);
}

That’s all there is to it. The built in LED is defined as an OUTPUT pin.

The sketch can be compiled and will run as the usual “Blink” example, with the addition of 4 quick flashes executed from the setup() function.

The next step is to import this sketch, unchanged, into PlatformIO.

Conversion to PlatformIO

In VSCode, if the “PlatformIO Home” page is not open, click on the “alien” head on the far left toolbar to open the PlatformIO Quick Access task list. Then, under “PIO Home” in the list of available tasks, select “open” and the PlatformIO Home page will open.

Import Arduino Project

On the PlatformIO Home page, click the “Import Arduino Project” button. Select a board, in my case it was an Uno, so I typed “uno” (without quotes) and it listed Arduino Uno.

Now navigate to where the Blink_multifile sketch lives and click the “Import” button. Wait a second or two and the sketch will be imported. It will be given a name similar to yymmdd-hhmmss-uno. You can save it with a different name later. The project will have been imported into your default location for PlatformIO projects.

If you open the src folder, you will see all the same files from the original sketch, with the same names.

Build Arduino Project

Click the normal toolbutton to build a sketch. It’s a “tick” or “checkmark” depending on where you live in the world. The sketch will compile quite happily and without any errors. You can upload it now to test the conversion, but we know it works already, so I’m not going to!

Convert `ino` files to `cpp`

This is easy! In VSCode, on the left side, open the file explorer if it isn’t already open. Right click each file in turn and rename it from *.ino to *.cpp. Ignore the prompt from VSCode that it doesn’t understand ino files and the offer to load an extension to make your life easier. It won’t!

That was easy, run another build to see if we have broken anything…

> Executing task in folder 201003-171408-uno: platformio run --target upload <

Processing uno (platform: atmelavr; board: uno; framework: arduino)
----------------------------------------------------------------------------------------------------------------------------------------
Verbose mode can be enabled via `-v, --verbose` option
CONFIGURATION: https://docs.platformio.org/page/boards/atmelavr/uno.html
PLATFORM: Atmel AVR (2.2.0) > Arduino Uno
HARDWARE: ATMEGA328P 16MHz, 2KB RAM, 31.50KB Flash
DEBUG: Current (simavr) On-board (simavr)
PACKAGES: 
 - framework-arduino-avr 5.0.0 
 - tool-avrdude 1.60300.200527 (6.3.0) 
 - toolchain-atmelavr 1.50400.190710 (5.4.0)
LDF: Library Dependency Finder -> http://bit.ly/configure-pio-ldf
LDF Modes: Finder ~ chain, Compatibility ~ soft
Found 5 compatible libraries
Scanning dependencies...
No dependencies
Building in release mode
Compiling .pio/build/uno/src/Blink_multifile.cpp.o
Compiling .pio/build/uno/src/flashLED.cpp.o
src/Blink_multifile.cpp: In function 'void setup()':
src/Blink_multifile.cpp:2:13: error: 'setupPins' was not declared in this scope
   setupPins();
             ^
src/Blink_multifile.cpp:3:18: error: 'flashLED' was not declared in this scope
   flashLED(4, 125);
                  ^
*** [.pio/build/uno/src/Blink_multifile.cpp.o] Error 1
src/flashLED.cpp:1:15: error: variable or field 'flashLED' declared void
 void flashLED(byte flashCount, int delayMS) {
               ^
src/flashLED.cpp:1:15: error: 'byte' was not declared in this scope
src/flashLED.cpp:1:32: error: expected primary-expression before 'int'
 void flashLED(byte flashCount, int delayMS) {
                                ^
*** [.pio/build/uno/src/flashLED.cpp.o] Error 1
====================================================== [FAILED] Took 0.73 seconds ======================================================
The terminal process "platformio 'run', '--target', 'upload'" terminated with exit code: 1.

That was unexpected, what happened? The Arduino happened, that’s what! Double click on Blink_multifile.cpp to open it in the editor and add these lines to the very top:

void setup();
void loop();
void setupPins();
void flashLED(byte flashCount, int delayMS);

Save and build again.

Compiling .pio/build/uno/src/flashLED.cpp.o
src/Blink_multifile.cpp:4:15: error: variable or field 'flashLED' declared void
 void flashLED(byte flashCount, int delayMS);
               ^
src/Blink_multifile.cpp:4:15: error: 'byte' was not declared in this scope
src/Blink_multifile.cpp:4:32: error: expected primary-expression before 'int'
 void flashLED(byte flashCount, int delayMS);
                                ^
src/Blink_multifile.cpp: In function 'void setup()':
src/Blink_multifile.cpp:8:18: error: 'flashLED' was not declared in this scope
   flashLED(4, 125);
                  ^
*** [.pio/build/uno/src/Blink_multifile.cpp.o] Error 1
src/flashLED.cpp:1:15: error: variable or field 'flashLED' declared void
 void flashLED(byte flashCount, int delayMS) {
               ^
src/flashLED.cpp:1:15: error: 'byte' was not declared in this scope
src/flashLED.cpp:1:32: error: expected primary-expression before 'int'
 void flashLED(byte flashCount, int delayMS) {
                                ^
*** [.pio/build/uno/src/flashLED.cpp.o] Error 1

Still a few errors. The first is in the file flashLED.cpp – the listed file name is flashLED.cpp.o but that’s the name of the object file that the compiler is creating. The source file is the given filename without the .o on the end.

Double-click on flashLED.cpp to open it in the editor.

The error is indicating that byte is not known. This is true, in C++ there isn’t a standard data type known as byte, it’s an Arduino thing. Add this line to the top of flashLED.cpp:

#include <stdint.h>

The angle brackets are required as this file is supplied with the compiler, and is a “system” header file.

Change the function header to the following:

void flashLED(int8_t flashCount, int delayMS)

We have replaced byte which is an 8 bit signed data type, with int8_t which is another, standard, 8 bit signed data type.

Edit Blink_multifile.cpp and make the same changes, add the #include and change the declaration of flashLED() to match the change above.

Save the file before running another build. We still have errors, the first of which is:

src/flashLED.cpp: In function 'void flashLED(int8_t, int)':
src/flashLED.cpp:7:10: error: 'byte' was not declared in this scope
     for (byte x = 0; x < flashCount; x++) {

Silly me, I forgot to check for more bytes. Edit flashLED.cpp again, and change byte to int8_t as before, then build again. More errors:

Compiling .pio/build/uno/src/loop.cpp.o
src/flashLED.cpp: In function 'void flashLED(int8_t, int)':
src/flashLED.cpp:8:22: error: 'LED_BUILTIN' was not declared in this scope
         digitalWrite(LED_BUILTIN, HIGH);
                      ^
src/flashLED.cpp:8:35: error: 'HIGH' was not declared in this scope
         digitalWrite(LED_BUILTIN, HIGH);
                                   ^
src/flashLED.cpp:8:39: error: 'digitalWrite' was not declared in this scope
         digitalWrite(LED_BUILTIN, HIGH);
                                       ^
src/flashLED.cpp:9:22: error: 'delay' was not declared in this scope
         delay(delayMS);
                      ^
src/flashLED.cpp:10:35: error: 'LOW' was not declared in this scope
         digitalWrite(LED_BUILTIN, LOW);

Now it looks like the compiler has forgotten what all the Arduino Language is about. Why is this?

One of the things that the Arduino IDE and Language hide from you is the fact that certain header files need to be #include'd. One of these is Arduino.h, so add the following line to flashLED.cpp just below the existing #include <stdint.h> line.

#include "Arduino.h"

This time, the file name is in double quotes as this is not a compiler supplied system header. This time, we appear to have a single error:

Compiling .pio/build/uno/src/loop.cpp.o
src/loop.cpp: In function 'void loop()':
src/loop.cpp:2:21: error: 'flashLED' was not declared in this scope
     flashLED(1, 1000);
                     ^
*** [.pio/build/uno/src/loop.cpp.o] Error 1

And it’s in loop.cpp this time. What’s up? Double-click to open the file.

The problem is, while we told Blink_multifile.cpp about all the other functions, we didn’t tell the other files about the functions. We need a new file, lets call it functions.h. Click the VSCode button for a new file (or File -> New File).

When the new empty tab appears, cut the #include <stdint.h> and the list of functions from Blink_multifile.cpp and paste them into the new tab. Save the file as functions.h in the PlatformIO project’s include folder, not in the original Arduino project. (Ask me how I know!)

Now edit `functions.h`` to make it look as follows:

#ifndef FUNCTIONS_H
#define FUNCTIONS_H

#include <stdint.h>
#include "Arduino.h"

void setup();
void loop();
void setupPins();
void flashLED(int8_t flashCount, int delayMS);

#endif  // FUNCTIONS_H

We’ve added the stdint.h and Arduino.h headers into this file too, for convenience.

Blink_multifile.cpp should be edited to look like this:

#include "functions.h"

void setup() {
  setupPins();
  flashLED(4, 125);
}

Loop.cpp also needs to be edited to resemble this:

#include "functions.h"

void loop() {
    flashLED(1, 1000);
}

Try another build. Let’s see how we are doing… still errors.

Building in release mode
Compiling .pio/build/uno/src/Blink_multifile.cpp.o
Compiling .pio/build/uno/src/flashLED.cpp.o
src/flashLED.cpp:3:15: error: variable or field 'flashLED' declared void
 void flashLED(int8_t flashCount, int delayMS) {
               ^
src/flashLED.cpp:3:15: error: 'int8_t' was not declared in this scope
src/flashLED.cpp:3:34: error: expected primary-expression before 'int'
 void flashLED(int8_t flashCount, int delayMS) {
                                  ^
*** [.pio/build/uno/src/flashLED.cpp.o] Error 1

It seems I forgot to tell flashLED.cpp about the stdint.h header file. As I’ve added that into functions.h, we might as well include that. Edit flashLED.h to resemble the following:

#include "functions.h"

void flashLED(int8_t flashCount, int delayMS) {
    if (!flashCount) 
        return;

    for (int8_t x = 0; x < flashCount; x++) {
        digitalWrite(LED_BUILTIN, HIGH);
        delay(delayMS);
        digitalWrite(LED_BUILTIN, LOW);
        delay(delayMS);
    }
}

Another build is called for I think. More errors, sigh!

Building in release mode
Compiling .pio/build/uno/src/flashLED.cpp.o
Compiling .pio/build/uno/src/loop.cpp.o
Compiling .pio/build/uno/src/setupPins.cpp.o
Archiving .pio/build/uno/libFrameworkArduinoVariant.a
src/setupPins.cpp: In function 'void setupPins()':
src/setupPins.cpp:2:13: error: 'LED_BUILTIN' was not declared in this scope
     pinMode(LED_BUILTIN, OUTPUT);
             ^
src/setupPins.cpp:2:26: error: 'OUTPUT' was not declared in this scope
     pinMode(LED_BUILTIN, OUTPUT);
                          ^
src/setupPins.cpp:2:32: error: 'pinMode' was not declared in this scope
     pinMode(LED_BUILTIN, OUTPUT);
                                ^
*** [.pio/build/uno/src/setupPins.cpp.o] Error 1

It looks like the setupPins() function has forgotten what LED_BUILTIN and OUTPUT are for. We need to add in the Arduino.h header in this file, to tell it. as we added that header file to our functions.h file, we can #include that here too. Edit setupPins.cpp and add the following line to the top:

#include "functions.h"

I wonder what will happen if we build it again?

Processing uno (platform: atmelavr; board: uno; framework: arduino)
----------------------------------------------------------------------------------------------------------------------------------------
Verbose mode can be enabled via `-v, --verbose` option
CONFIGURATION: https://docs.platformio.org/page/boards/atmelavr/uno.html
PLATFORM: Atmel AVR (2.2.0) > Arduino Uno
HARDWARE: ATMEGA328P 16MHz, 2KB RAM, 31.50KB Flash
DEBUG: Current (simavr) On-board (simavr)
PACKAGES: 
 - framework-arduino-avr 5.0.0 
 - toolchain-atmelavr 1.50400.190710 (5.4.0)
LDF: Library Dependency Finder -> http://bit.ly/configure-pio-ldf
LDF Modes: Finder ~ chain, Compatibility ~ soft
Found 5 compatible libraries
Scanning dependencies...
No dependencies
Building in release mode
Compiling .pio/build/uno/src/setupPins.cpp.o
Compiling .pio/build/uno/FrameworkArduino/CDC.cpp.o
Compiling .pio/build/uno/FrameworkArduino/HardwareSerial.cpp.o
Compiling .pio/build/uno/FrameworkArduino/HardwareSerial0.cpp.o
Compiling .pio/build/uno/FrameworkArduino/HardwareSerial1.cpp.o
Compiling .pio/build/uno/FrameworkArduino/HardwareSerial2.cpp.o
Compiling .pio/build/uno/FrameworkArduino/HardwareSerial3.cpp.o
Compiling .pio/build/uno/FrameworkArduino/IPAddress.cpp.o
Compiling .pio/build/uno/FrameworkArduino/PluggableUSB.cpp.o
Compiling .pio/build/uno/FrameworkArduino/Print.cpp.o
Compiling .pio/build/uno/FrameworkArduino/Stream.cpp.o
Compiling .pio/build/uno/FrameworkArduino/Tone.cpp.o
Compiling .pio/build/uno/FrameworkArduino/USBCore.cpp.o
Compiling .pio/build/uno/FrameworkArduino/WInterrupts.c.o
Compiling .pio/build/uno/FrameworkArduino/WMath.cpp.o
Compiling .pio/build/uno/FrameworkArduino/WString.cpp.o
Compiling .pio/build/uno/FrameworkArduino/abi.cpp.o
Compiling .pio/build/uno/FrameworkArduino/hooks.c.o
Compiling .pio/build/uno/FrameworkArduino/main.cpp.o
Compiling .pio/build/uno/FrameworkArduino/new.cpp.o
Compiling .pio/build/uno/FrameworkArduino/wiring.c.o
Compiling .pio/build/uno/FrameworkArduino/wiring_analog.c.o
Compiling .pio/build/uno/FrameworkArduino/wiring_digital.c.o
Compiling .pio/build/uno/FrameworkArduino/wiring_pulse.S.o
Compiling .pio/build/uno/FrameworkArduino/wiring_pulse.c.o
Compiling .pio/build/uno/FrameworkArduino/wiring_shift.c.o
Archiving .pio/build/uno/libFrameworkArduino.a
Indexing .pio/build/uno/libFrameworkArduino.a
Linking .pio/build/uno/firmware.elf
Building .pio/build/uno/firmware.hex
Checking size .pio/build/uno/firmware.elf
Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [          ]   0.4% (used 9 bytes from 2048 bytes)
Flash: [          ]   3.1% (used 1008 bytes from 32256 bytes)
===================================================== [SUCCESS] Took 2.62 seconds =====================================================

Hooray! after much wailing and gnashing of teeth, we have a build. Does it work? Try uploading, click the “->” toolbar button after plugging in your board of course. Of course it works!

Bonus - Convert to AVR C++

At this point, you can settle down and watch the LED blinking away every second if you wish, or, you can delve a little into the bowels of AVR C++. Before we head off, check this out:

Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [          ]   0.4% (used 9 bytes from 2048 bytes)
Flash: [          ]   3.1% (used 1008 bytes from 32256 bytes)

The Arduino sketch used 9 bytes of Static RAM, plus 1,008 bytes of Flash RAM. It’s not a lot I admit, especially when we have 2 Kb Static RAM and 32 Kb Flash RAM to play with, but sometimes it’s too much. People with 3D printers running Marlin often have to decide which features to leave out to fit in some new feature that they absolutely must have, space is limited, even with 32 Kb to fill.

Edit the Header File

Open functions.h and change it to resemble the following:

#ifndef FUNCTIONS_H
#define FUNCTIONS_H

#include <stdint.h>

// We need this to get the ATmega328p's register and pin names.
#include "avr/io.h"

// We are no longer in Arduino land.
#define LED_BUILTIN 13

void setup();
void loop();
void setupPins();
void flashLED(int8_t flashCount, int delayMS);

#endif  // FUNCTIONS_H

You will note a serious lack of a semicolon at the end of the #define, that is correct!

Edit setupPins.cpp

The setupPins.cpp file is next for editing. Currently it looks like this:

#include "functions.h"

void setupPins() {
    pinMode(LED_BUILTIN, OUTPUT);
}

Change it to the following:

#include "functions.h"

void setupPins() {
    DDRB |= (1 << DDB5);
}

Don’t ask questions at the back, all will become clear.

Edit flashLED.cpp

It’s time to change flashLED.cpp now, it currently looks like this:

#include "functions.h"

void flashLED(int8_t flashCount, int delayMS) {
    if (!flashCount) 
        return;

    for (int8_t x = 0; x < flashCount; x++) {
        digitalWrite(LED_BUILTIN, HIGH);
        delay(delayMS);
        digitalWrite(LED_BUILTIN, LOW);
        delay(delayMS);
    }
}

It has lots of Arduino specific language there, we need to remove it all. Edit away and keep editing until it looks like this instead:

#include "functions.h"
#include "util/delay.h"

void flashLED(int8_t flashCount, int delayMS) {
    if (!flashCount) 
        return;

    for (int8_t x = 0; x < (flashCount * 2); x++) {
        PINB |= (1 << PINB5);
        _delay_ms(delayMS);
    }
}

You will see that we have changed the for loop to double the supplied flashCount value. I’ll explain in a bit.

First Build

Build the new version of our sketch. I see these errors:

Building in release mode
Compiling .pio/build/uno/src/Blink_multifile.cpp.o
Compiling .pio/build/uno/src/flashLED.cpp.o
Compiling .pio/build/uno/src/loop.cpp.o
Compiling .pio/build/uno/src/setupPins.cpp.o
Linking .pio/build/uno/firmware.elf
/tmp/ccDTBT41.ltrans0.ltrans.o: In function `main':
<artificial>:(.text.startup+0x86): undefined reference to `setup'
<artificial>:(.text.startup+0x8e): undefined reference to `loop'
collect2: error: ld returned 1 exit status
*** [.pio/build/uno/firmware.elf] Error 1

So, what’s going on? Setup() and loop() are Arduino functions, and we are no longer using the Arduino framework. Well, actually, we still are, and the Arduino supplied main() function is still linked with our sketch code, and is calling both the setup() and loop() functions.

The use of the Arduino framework is defined in platformio.ini, so we need to change that file to inform PlatformIO that we no longer wish to use that framework. Edit platformio.ini file and remove the framework = arduino line. It should look like this, with all comments removed as well:

[env:uno]
platform = atmelavr
board = uno

Now we are running with the wolves and using plain AVR C++ as opposed to any framework language. Let’s do another build and see what happens:

Building in release mode
Compiling .pio/build/uno/src/Blink_multifile.o
Compiling .pio/build/uno/src/flashLED.o
Compiling .pio/build/uno/src/loop.o
Compiling .pio/build/uno/src/setupPins.o
Linking .pio/build/uno/firmware.elf
/home/norman/.platformio/packages/toolchain-atmelavr/bin/../lib/gcc/avr/5.4.0/../../../../avr/lib/avr5/crtatmega328p.o:(.init9+0x0): undefined reference to `main'
collect2: error: ld returned 1 exit status
*** [.pio/build/uno/firmware.elf] Error 1

We took away the Arduino supplied main() function when we omitted the Arduino framework, but we didn’t replace it. We still have the setup() and loop() functions lying around, so lets now create a replacement main() function and include those as best we can.

Edit Blink_multifile.cpp.

Edit the Blink_multifile.cpp file and make it look like this:

#include "functions.h"


int main() {
    // Setup here
    setupPins();
    flashLED(4, 125);

    // Loop here
    loop();
}

The old setup() function is gone, but the contents remain. The Arduino supplied loop() function gets called in a, ahem, loop, where it is called, exits, called again, exists again, over and over. The setup and breakdown of the function call is a tad excessive. In this version, we call loop() once. That means that loop() itself has to do the looping for us.

Edit loop.cpp

Edit the loop.cpp file and change it to the following:

#include "functions.h"

void loop() {
    while (1) {
        flashLED(1, 1000);
    }
}

You can see that I have added a simple while loop. I could have made this even more efficient by increasing the number of flashes in each call, but I leave that as an “exercise for the reader”! as we authors say when we feel a cop out coming on!

Final Build

Build the project again. It will compile without error. But look at the stats at the end:

Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [          ]   0.0% (used 0 bytes from 2048 bytes)
Flash: [          ]   0.6% (used 202 bytes from 32256 bytes)

We have used zero bytes of Static RAM and only 202 bytes of Flash Ram. That’s down from 9 Static RAM bytes and 1,008 Flash Ram bytes. Sometimes this makes the difference between getting a sketch to fit your board, or not.

Ok, I could get it even smaller by merging loop.cpp and flashLED.cpp into the main loop in the Blink_multifile.cpp but that’s another exercise for the user!

What Did I do?

Look away now if you don’t want the technical details…

The Arduino Function pinMode() tells a single pin whether it is to be an input or an output pin. Input pins can have the options of enabling the pullup resistors. PinMode() does a lot of additional work in the background to disconnect certain pins from timers (for PWM) and so on. There is a bit of error checking going on as well.

In the end, pinMode() boils down to setting a single bit in one of the ATmega328’s “DDR” registers. The builtin LED pin, D13, is actually the Atmega328p’s pin 5 on the PORTB port. Each GPIO pin on the microcontroller has one of each of these registers hidden away internally:

A data Direction Register (DDRx);
A PORTx register for output pins;
A PINx register for input pins.

To make a pin an output, we set its corresponding bit in the DDR register for it’s PORT. In the case of D13, we are pin 5 on PORTB, so bit 5 in DDRB needs to be set to a 1. That is all that setupPins() now has to do.

There are two ways to flash an LED attached to an output pin. The first is to set the correct bit in the PORT register to a 1, wait a little while, then clear the same bit back to a 0 and delay again. That’s too much like hard work but would resemble this for D13:

PORTB |= (1 << PORTB5);
_delay_ms(1000);
PORTB &= ~(1 << PORTB5);
_delay_ms(1000);

The first command ORs a 1 into the correct bit position, bit 5 in the PORTB register. Then we delay, then we AND a 0 into the same bit position. then another delay. These two operations, and delays, flash the LED once.

As I said, too much work. The designers of the ATmega328p decided that as the PIN register is not needed for an output pin, it can be used for other things. If you write a 1 to the correct bit in the pin’s PIN register, the pin will toggle. If it was on, it will be off and if it was off, it will turn on. To flash an LED, you need to turn it on then off, so this is what flashLED() now does, and is why I had to double the flashCount value. To get one flash of the LED, we need two toggles of the pin.

The code:

PINB |= (1 << PINB5);
_delay_ms(delayMS);

toggles the pin and delays a bit. If we do this twice we get one flash. Job done.

The Arduino function digitalWrite() takes a lot of instructions to do error checking and so on, before it gets down to the nitty gritty of turning the pin on or off. The above PINB |= (1 << PINB5) instruction does it in one step. This vastly reduces the size of your compiled sketch and allows more code to be fitted into the board.

The End.

Just before I go, this version of Blink_multifile.cpp is actually all you need. The other files can be deleted.

#include "util/delay.h"

int main() {
    // Setup here
    DDRB |= (1 << DDB5);

    for (uint8_t x = 0; x < 8; x++) {
        PINB |= (1 << PINB5);
        _delay_ms(125);
    }

    // Loop here
    while (1) {
        PINB |= (1 << PINB5);
        _delay_ms(1000);
    }
}

This version compiles down to:

Advanced Memory Usage is available via "PlatformIO Home > Project Inspect"
RAM:   [          ]   0.0% (used 0 bytes from 2048 bytes)
Flash: [          ]   0.6% (used 182 bytes from 32256 bytes)

We are now down to 182 bytes of Flash RAM from 202. Not bad considering is still does what the original sketch did.

HTH

Cheers,
Norm.