error on incompatible hardware

spybug/spybug.ino

@@ -61,6 +61,10 @@
  END USER CONFIGURATION
  **********************/
 
+#if !defined(__AVR_ATmega328P__) || F_CPU != 16000000
+#error "This program only works on ATmega328P devices with a clock frequency of 16MHz!"
+#endif
+
 void (*full_reset)() = nullptr;
 
 static int serial_putch(char c, FILE *f) {
@@ -130,7 +134,7 @@ ISR (WDT_vect) {
 /* Based on https://github.com/rocketscream/Low-Power. */
 static void low_power_sleep_minutes(unsigned long t) {
 	wdt_int_sleep_mode = true;
-	ADCSRA &= ~(1 << ADEN); /* Disable ADC. */
+	ADCSRA &= ~_BV(ADEN); /* Disable ADC. */
 	for (unsigned long i = 0; 8ul * i < 60ul * t; i++) {
 		// Power Down for 8s
 		wdt_enable(WDTO_8S);   /* Start watchdog timer for 8s. */
@@ -146,7 +150,7 @@ static void low_power_sleep_minutes(unsigned long t) {
 			sei();
 		} while (0);
 	}
-	ADCSRA |= (1 << ADEN); /* Re-enable ADC. */
+	ADCSRA |= _BV(ADEN); /* Re-enable ADC. */
 	wdt_int_sleep_mode = false;
 }