Add example code

src/blink.c

+#include <avr/io.h>
+#include <util/delay.h>
+
+int main()
+{
+	/* Turn off default prescaling of clock (AT90USB DS, p. 48) */
+	CLKPR = (1 << CLKPCE);
+	CLKPR = 0;
+	DDRB=_BV(PB7); //sets the data direction register of Port B to output on PB7
+	while(1)
+	{
+		PORTB=_BV(PB7); //Outputs 1 on PB7
+		_delay_ms(200);
+		PORTB=0; //Stops output on port B
+		_delay_ms(200);
+	}
+}
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