Changed approach to F_CPU to be user-defined

Author: Roy, Elizabeth

cores/arduino/wiring.c

@@ -272,146 +272,49 @@ void init()
 	// this needs to be called before setup() or some functions won't
 	// work there
 
-/*************************** GET VCC & FUSE SETTING ***************************/
-
-
-	/* Measure VDD using ADC */
-	uint8_t supply_voltage;
-	
-	/* Initialize AC reference (what we are measuring) - 1.5V known */
-	VREF.CTRLA |= VREF_AC0REFSEL_1V5_gc;	
-	
-	/* Enable AC reference */
-	VREF.CTRLB |= VREF_AC0REFEN_bm;
-
-	/* DAC to max -- output reference voltage */
-	AC0.DACREF = 0xFF;
-	
-	/* Enable DAC REF by selecting it as input and enabling AC */
-	AC0.MUXCTRLA |= AC_MUXNEG_DACREF_gc;
-	AC0.CTRLA |= ADC_ENABLE_bm;
-
-	/* Initialize ADC reference (VDD) */
-	ADC0.CTRLC = ADC_REFSEL_VDDREF_gc;
-	
-	/* Initialize MUX (DAC/AC reference from VREF) */
-	ADC0.MUXPOS = ADC_MUXPOS_DACREF_gc;
-	
-	/* Enable ADC */
-	ADC0.CTRLA |= ADC_ENABLE_bm;
-	
-	/* Start a conversion */
-	ADC0.COMMAND |= ADC_STCONV_bm;
-	
-	/* Wait until result is ready */
-	while(!(ADC0.INTFLAGS & ADC_RESRDY_bm));
-	
-	/* Result ready */
-	/* supply_voltage = (VIN * 1024)/result where VIN = 1.5V from VREF */
-	uint16_t adc_result = ADC0.RES;
-	
-	uint16_t voltage = (15 * 1024) / adc_result; /* using 1.5 << 1 to avoid using float */
-	
-	/* Only for the purposes of staying within safe operating range -- approximate */
-	if(voltage >= 48){ /* 4.8V+ -> 5V */
-		supply_voltage = VCC_5V0;
-	} else if (voltage >= 30){ /* 3V-4V7 -> 3V3 */
-		supply_voltage = VCC_3V3;
-	} else { /* < 3V -> 1V8 */
-		supply_voltage = VCC_1V8;
-	}
-	
-	/* Fuse setting for 16/20MHz oscillator */
-	uint8_t fuse_setting = FUSE.OSCCFG & FUSE_FREQSEL_gm;
-	
-	/* Deinitialize ADC, AC & VREF */
-	ADC0.CTRLA = 0x00;
-	ADC0.MUXPOS = 0x00;	
-	ADC0.CTRLC = 0x00;		
-	
-	AC0.CTRLA = 0x00;	
-	AC0.MUXCTRLA = 0x00;	
-	AC0.DACREF = 0xFF;	
-	
-	VREF.CTRLB = 0x00;	
-	VREF.CTRLA = 0x00;
-
 /******************************** CLOCK STUFF *********************************/
 
+	/* We assume 5V operating frequency and FUSE.OSCCFG -> 16MHz */
+
  	int64_t cpu_freq;
 
- 	#if (PERFORM_SIGROW_CORRECTION_F_CPU == 1)
- 	int8_t sigrow_val = 0;
- 	#endif
-
- 	/* Initialize clock divider to stay within safe operating area */
-
- 	if(supply_voltage >= VCC_5V0){
-	 	
-	 	/* Disable system clock prescaler - F_CPU should now be ~16/20MHz */
-	 	_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, 0x00);
-	 	
-	 	/* Assign cpu_freq value and sigrow_val depending on fuse setting */
-	 	if(fuse_setting == FREQSEL_20MHZ_gc){
-		 	cpu_freq = 20000000;
-		 	
-		 	#if (PERFORM_SIGROW_CORRECTION_F_CPU == 1)
-		 	sigrow_val = SIGROW.OSC20ERR5V;
-		 	#endif
-
-		 } else { /* fuse_setting == FREQSEL_16MHZ_gc */
-		 	cpu_freq = 16000000;
-
-		 	#if (PERFORM_SIGROW_CORRECTION_F_CPU == 1)
-		 	sigrow_val = SIGROW.OSC16ERR5V;
-		 	#endif
-
-	 	}
-	 	
-	 } else if (supply_voltage == VCC_3V3) {
-	 	
-	 	/* Enable system clock prescaler to DIV2 - F_CPU should now be ~8/10MHz */
-	 	_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, (CLKCTRL_PEN_bm | CLKCTRL_PDIV_2X_gc));
-	 	
-	 	/* Assign cpu_freq value and sigrow_val depending on fuse setting */
-	 	if(fuse_setting == FREQSEL_20MHZ_gc){
-		 	cpu_freq = 10000000;
-		 	
-		 	#if (PERFORM_SIGROW_CORRECTION_F_CPU == 1)
-		 	sigrow_val = SIGROW.OSC20ERR3V;
-		 	#endif
-
-		 } else { /* fuse_setting == FREQSEL_16MHZ_gc */
-		 	cpu_freq = 8000000;
-		 	
-		 	#if (PERFORM_SIGROW_CORRECTION_F_CPU == 1)
-		 	sigrow_val = SIGROW.OSC16ERR3V;
-		 	#endif
-	 	}
-	 	
-	 } else {
-	 	/* Shouldn't get here but just in case... */
-	 	
-	 	/* Enable system clock prescaler to DIV4 - F_CPU should now be ~4/5MHz */
-	 	_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, (CLKCTRL_PEN_bm | CLKCTRL_PDIV_4X_gc));
-	 	
-	 	
-	 	if(fuse_setting == FREQSEL_20MHZ_gc){
-		 	cpu_freq = 5000000;
-		 	#if (PERFORM_SIGROW_CORRECTION_F_CPU == 1)
-		 	sigrow_val = SIGROW.OSC20ERR3V;
-		 	#endif
-		 	
-		 } else { /* fuse_setting == FREQSEL_16MHZ_gc */
-		 	cpu_freq = 4000000;
-		 	#if (PERFORM_SIGROW_CORRECTION_F_CPU == 1)
-		 	sigrow_val = SIGROW.OSC16ERR3V;
-		 	#endif
-	 	}
- 	}
+	#if (F_CPU == 16000000)
+		cpu_freq = 16000000;
+		
+		/* No division on clock */
+		_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, 0x00);
+		
+	#elif (F_CPU == 8000000)
+		cpu_freq = 8000000;
+		
+		/* Clock DIV2 */
+		_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, (CLKCTRL_PEN_bm | CLKCTRL_PDIV_2X_gc));
+		
+	#elif (F_CPU == 4000000)
+		cpu_freq = 4000000;
+		
+		/* Clock DIV4 */
+		_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, (CLKCTRL_PEN_bm | CLKCTRL_PDIV_4X_gc))
+		
+	#elif (F_CPU == 2000000)
+		cpu_freq = 2000000;
+		
+		/* Clock DIV8 */
+		_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, (CLKCTRL_PEN_bm | CLKCTRL_PDIV_8X_gc))
+	#else
+		# warning "F_CPU not defined OR defined as an invalid value"
+		
+	//#define F_CPU 16000000
+		cpu_freq = 16000000;
+				
+		/* No division on clock */
+		_PROTECTED_WRITE(CLKCTRL_MCLKCTRLB, 0x00);
+	#endif
+
 
  	#if (PERFORM_SIGROW_CORRECTION_F_CPU == 1)
  	/* Calculate actual F_CPU with error values from signature row */
+	uint8_t sigrow_val = SIGROW.OSC16ERR5V;
  	cpu_freq *= (1024 + sigrow_val);
  	cpu_freq /= 1024; 	
  	#endif /* (CORRECT_F_CPU == 1) */