README.md

Outline for "Intro to C using Atmel/Arduino"

Lesson 1:

Requirements:

• 1 Arduino Uno (with ATmega328p).
• brew install avr-gcc avrdude

• Warm-up: write the blink program for Arduino.
• Now write it using C, avr-gcc and avrdude.
• Turn it into a benchmark: blink 1,000,000 times and then spin.
• Compare the time to 1,000,000 blinks for Arduino vs C.

Resources:

• ATmega328p datasheet, appnotes: https://www.microchip.com/wwwproducts/en/ATmega328p
• avr-gcc wiki: https://gcc.gnu.org/wiki/avr-gcc
• avr libc: https://www.nongnu.org/avr-libc/
  • https://www.nongnu.org/avr-libc/user-manual/group__demo__project.html
• adafruit avr-gcc blinky tutorial: https://www.ladyada.net/learn/proj1/blinky.html

For the Arduino sketch:

• use pinMode() and digitalWrite().

blink.c

#include <avr/io.h>
#include <stdint.h>

int main() {
    // pinMode(13, OUTPUT);
    DDRB = 0b00100000;

    while (1) {
        // digitalWrite(13, HIGH);
        PORTB = 0b00100000;

        // delay(x);
        for (uint16_t i=0; i < UINT16_MAX; i++) {
            ;
        }

        // digitalWrite(13, LOW);
        PORTB = 0b00000000;

        // delay(x);
        for (uint16_t i=0; i < UINT16_MAX; i++) {
            ;
        }
    }
}

Makefile

blink.hex: blink.elf
	avr-objcopy -O ihex blink.elf blink.hex

blink.elf: blink.o
	avr-gcc -DF_CPU=16000000 -mmcu=atmega328 -o blink.elf blink.o

blink.o: blink.c
	avr-gcc -DF_CPU=16000000 -mmcu=atmega328 -o blink.o -c blink.c

flash: blink.hex
	avrdude -c arduino -p atmega328p -P /dev/tty.wchusbserial1420 -U flash:w:blink.hex

clean:
	rm -f blink.o blink.elf blink.hex

.PHONY: flash clean