CLOCK System with Baremetal C

This project walks you through the process building an AVR application to exercise the clock and timer/counter on the ATMega328p microcontroller.

Prerequisites

We need to install library, compiler, binary to hex converter, and AVR MCU programmer

These applications can be install by following line:

sudo apt install avr-libc avrdude binutils-avr gcc-avr

The Code

The code below initializes the clock module and prepares them for use. The while loop toggles a led on the microcontroller once per 0.25 seconds.

int main() {

    // Set PORTB5 (built-in led) as output
    DDRB |= _BV(DDB5);

    // Initialize clock
    CLOCK_Init();

    // Enable global interrupts
    sei();

    while(1) {

        // Toggle led
        PORTB ^= _BV(PORTB5);

        // Sleep 250 millisecond (0.25 second)
        CLOCK_DelayMs(250);

    }


    return 0;
}

Notice the line of code listed below. This sets the global interrupt flag in SREG enabling interrupts. Since we are using the AVR's service interrupt routine to increase clock/timer on every milliseconds.

sei();

Compiling The Code

To compile the source code we need to create a Makefile to automate the process. Makefiles allow us to place all build/clean/flash commands into one easy to use file. Each microcontroller has a unique set of parameters prior to compiling and deploying. These commands are listed a the top of the Makefile and are easily changed.

Now that your Makefile is complete issue the make from the command start the build process.

make all

Flashing The Code

Now that we compiled the code we can deploy to our microcontroller.

make flash