/*
  Blink
  Turns on an LED on for one second, then off for one second, repeatedly.

  The LED on the Blue Pill is connected to PC13
*/


// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin PC13 as an output.
  pinMode(PC13, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(PC13, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);              // wait for a second
  digitalWrite(PC13, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);              // wait for a second
}

/*
 Timer Interrupt
 Using timer 2 to give a flag when an overflow occured.
 Use polling this flag to time programs 
*/
uint16_t timer_value = 0x8FFF;
int prescalefactor = 400;
volatile bool timer_tick = false;//timer_tick is changed in the Interrupt Service Routine
HardwareTimer timer(2);
void overflowISR();


void setup() {
pinMode(PC13, OUTPUT);// here is the internal LED attached to
timer.pause();
timer.setPrescaleFactor(prescalefactor);
timer.setOverflow(timer_value);
timer.refresh();
timer.attachInterrupt(4, overflowISR);
}

void loop() {
  timer.resume();//start timer2
while(1){
  while(!timer_tick){} //poll for timer_tick
  timer_tick=false; //reset timer_tick
  digitalWrite(PC13, !digitalRead(PC13));//invert LED port
  }
}

void overflowISR()
{
  timer_tick=true;//here is the timer flag set
}

/*
 MIDI using the TX1 of UART1 at pin PA9  
*/

uint8_t channel = 10;//I used the percussion channel 10
uint8_t velocity = 64;// half max value
// plays a midi note on TX1 @ PA9
//check in calling routine for max cmd, pitch and velocity
void noteOn(char cmd, char pitch, char velocity) {
    Serial1.print(cmd);
    Serial1.print(pitch);
    Serial1.print(velocity);
}

void setup(void) {
pinMode(PA9, OUTPUT);// this is the TX1 pin
// Set MIDI baud rate to 31250 Bps:
Serial1.begin(31250);
}

void loop(void) {
while (1){
// Play notes from F#-0 (0x1E) to F#-5 (0x5A):
    for (uint8_t note = 0x1E; note < 0x5A; note++) {
         noteOn((0x90+channel), note, velocity);
        delay(10);
//noteOff can be this:
        noteOn((0x90+channel), note, 0x00);//velocity = 0x00 means noteOff
//or use for noteOff:
       //noteOn((0x80+channel), note, velocity);        
        delay(100);   
   }
  }
}

/*
Using SPI  
*/
#include <Arduino.h>
#include <SPI.h>
#define SPI_CS0 PA2 // three chip-select lines, but can be more
#define SPI_CS1 PA3
#define SPI_CS2 PA4
#define SPI_CLK PA5
#define SPI_MOSI PA7
#define SPI_MISO PA6

void setup() {
pinMode(SPI_CS0, OUTPUT);
pinMode(SPI_CS1, OUTPUT);
pinMode(SPI_CS2, OUTPUT); 
SPI.begin();
//here set your spi freq and mode
SPI.beginTransaction(SPISettings(10000000, MSBFIRST, SPI_MODE3)); 
}

void loop() {

 delay(10);
  // writing to the SPI
  // take the SS (using CS0) pin low to select the chip:
  digitalWrite(SPI_CS0, LOW);
  //  send in the address and value via SPI:
  SPI.transfer(0x3F);//some data to be send
  SPI.transfer(0xAA);
  SPI.transfer(0x55);
  // take the SS pin high to de-select the chip:
  digitalWrite(SPI_CS0, HIGH);//done
 }