/* power saving mode, mcu runs significantly cooler
    * Sysclock 240 Mhz, bus clocks 120 Mhz */
  void SysClkHalfSpeed();

  /* full speed - sysclk from PLL1 P - 480 Mhz
   * Sysclock 480 Mhz, bus clocks 240 Mhz */
  void SysClkFullSpeed()

#include <Arduino.h>
#include <math.h>
#include "whetstone.h"

enum EnCpuSp {
	SPFULL = 0,
	SPHALF
};

void cpusetspeed(EnCpuSp speed);
void checkcmd(void);
void printtempvbat(void);
void cosfade();
void EnableCache();
void sleep(uint16_t ms);

int ledPin = LED_BUILTIN;
int print = false;

//used by cosfade()
#define PER 15
#define REP 20
int8_t led = 0;
int n = PER, cnt = 0;
uint8_t p = 0;

// the setup() method runs once when the sketch starts
void setup() {
	EnableCache();

	//initialize the digital pin as an output:
	pinMode(ledPin, OUTPUT);
	digitalWrite(ledPin, LOW);

	pinMode(ATEMP, INPUT_ANALOG);
	pinMode(AVREF, INPUT_ANALOG);

	pinMode(USER_BTN, INPUT_PULLDOWN);
}

//the loop() method runs over and over again, 
void loop() {
	checkcmd();
	if (print && n == 0 && cnt == 0) printtempvbat();
	cosfade();
}

/* a half hearted attempt to make a 'breathing' led, works quite well though */
void cosfade() {
  digitalWrite(LED_BUILTIN,led);
  led = ~led & 1;
  if(led)
    delay(PER-p);
  else
    delay(p);
  if(cnt>REP) {
	  float nf, perf;
	  n = n>PER?0:n+1;
	  nf = n * 1.0;
	  perf = PER * 1.0;
	  p = perf * ( cos(2 * PI * nf/perf) / 2.0 + 0.5 );
	  cnt=0;
  } else
	  cnt++;
}

void printtempvbat() {
	uint16_t vrefint = analogRead(AVREF);
	Serial.print("Vref int (1.21v):");
	Serial.print(vrefint);
	Serial.println();

	uint16_t vtemp = analogRead(ATEMP);
	Serial.print("temp sensor:");
	Serial.print(vtemp);
	Serial.println();

	uint16_t mv = (1210 * vtemp) / vrefint;
	Serial.print("mvolt:");
	Serial.print(mv);
	Serial.println();

	// specs 5.3.22 temp sensor characteristics
	// V 30 deg ~ 0.62v
	// slope 2 mv/C
	uint16_t v30 = 620;
	float temp = (mv - v30) * 1.0 / 2.0 + 30.0;
	Serial.print("temp:");
	Serial.print(temp);
	Serial.println();
}

void cpusetspeed(EnCpuSp speed) {
	if (speed == EnCpuSp::SPHALF) {
		SysClkHalfSpeed();
	} else {
		SysClkFullSpeed();
	}
}

void checkcmd() {
	if(Serial.available()) {
		char r = Serial.read();
		if(r=='p') {
			print = ! print;
		} else if (r=='w') {
			//whetstone(F_CPU/1000000);
			whetstone(SystemCoreClock/1000000);
		} else if (r=='C') {
			cpusetspeed(EnCpuSp::SPFULL);
			Serial.print("sysclock Mhz:");
			Serial.println(SystemCoreClock/1000000);
		} else if (r=='c') {
			cpusetspeed(EnCpuSp::SPHALF);
			Serial.print("sysclock Mhz:");
			Serial.println(SystemCoreClock/1000000);
		} else {
			Serial.println("p - print/stop print");
			Serial.println("C - cpu full speed");
			Serial.println("c - cpu half speed");
			Serial.println("w - run whetstone");
		}
	}

	if (digitalRead(USER_BTN) == HIGH) {
		Serial.println("user btn pressed");
	}
}

void blinks() {
	for (int i = 0; i < 5; i++) {
		digitalWrite(LED_BUILTIN, HIGH);
		delay(100);
		digitalWrite(LED_BUILTIN, LOW);
		delay(100);
	}
}

void EnableCache() {
	SCB_CleanDCache();
	__DSB();
	SCB_InvalidateDCache();
	SCB_EnableDCache();
	__ISB();
	SCB_InvalidateICache();
	SCB_EnableICache();
}

void sleep(uint16_t ms) {
	for(uint16_t i=0; i<ms; i++)
		asm("wfi");
}

p - print/stop print
C - cpu full speed
c - cpu half speed
w - run whetstone
Vref int (1.21v):376  <<< type 'p' print the cpu temperature
temp sensor:205
mvolt:659
temp:49.50
Beginning Whetstone benchmark at 480 MHz ...  <<< type 'w' run whetstone benchmark

Loops:10000, Iterations:1, Duration:1627.57 millisec
C Converted Single Precision Whetstones:614.41 Mflops

sysclock Mhz:240 <<< typed 'c' here to reduce system clock to 240 Mhz

Vref int (1.21v):375
temp sensor:205
mvolt:661
temp:50.50
Beginning Whetstone benchmark at 240 MHz ...   <<< type 'w' run whetstone benchmark

Loops:10000, Iterations:1, Duration:3251.76 millisec
C Converted Single Precision Whetstones:307.53 Mflops
Vref int (1.21v):376
temp sensor:202
mvolt:650
temp:45.00
user btn pressed  <<< --- press user button on board
user btn pressed
user btn pressed