Teensy Timer/Counter Example for the T3 & T3.1

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Maybe not fully respond your question but this can help to buildUp precise timers based on isr.
Teensy3 has IntervalTimer in core (used for Tone) that it's easy to use:

Code: 
IntervalTimer myTimer;

void setup(void) {
myTimer.begin(myCallback,1000L*1000); // 1 second
}

void loop(){
}

void myCallback(){
//...do something
}

You don't need to include IntervalTimer.h since it's in core.

You can take a look inside hardware/teensy/cores/teensy3/IntervalTimer.h (..and IntervalTimer.cpp) how it's done
 
sumotoy said:
Maybe not fully respond your question but this can help to buildUp precise timers based on isr.
Teensy3 has IntervalTimer in core (used for Tone) that it's easy to use:

Code: 
IntervalTimer myTimer;

void setup(void) {
myTimer.begin(myCallback,1000L*1000); // 1 second
}

void loop(){
}

void myCallback(){
//...do something
}

You don't need to include IntervalTimer.h since it's in core.

You can take a look inside hardware/teensy/cores/teensy3/IntervalTimer.h (..and IntervalTimer.cpp) how it's done
Click to expand...

Not really but I see Paul did allready set the FlexTimer Registers in the mk20dx128.h
 
Did something but the Prescaler seems not to work

Code: 
volatile uint32_t actually;
volatile uint32_t old = 0;

#define FTM0_WPEN  0x40

void setup() {
  // Write Protection Disable
  FTM0_MODE |= FTM_MODE_WPDIS;
  
  FTM0_MODE |= FTM_MODE_FTMEN;
  
  // enable Overflow Interrupt
  FTM0_SC |= FTM_SC_TOIE;
  
  // enable the clock for FTM0
  FTM0_SC |= FTM_SC_CLKS(0b11);
  // 00 No clock selected. This in effect disables the FTM counter.
  // 01 System clock
  // 10 Fixed frequency clock
  // 11 External clock

  // set Prescaler 
  //FTM0_SC |= FTM_SC_PS(0b111);
  FTM0_SC |= 0b110;
  // 000 Divide by 1
  // 001 Divide by 2
  // 010 Divide by 4
  // 011 Divide by 8
  // 100 Divide by 16
  // 101 Divide by 32
  // 110 Divide by 64
  // 111 Divide by 128
  
  // set the counter initial value
  FTM0_CNT = 0;
  
  // enable the clock for FTM0
  SIM_SCGC6 |= SIM_SCGC6_FTM0;
  
  // enable IRQ Interrupt
  NVIC_ENABLE_IRQ(IRQ_FTM0);
  
  FTM0_FMS |= FTM0_WPEN;
  
  // initialize serial
  Serial.begin(115200);
}

void loop() {
  // nothing
  //Serial.println(FTM0_CNT);
}

void ftm0_isr() {
  actually = micros();
  Serial.print("ECHO ");
  Serial.println(actually - old);
  old = actually;
  
  //Serial.println(FTM0_CNT);
}

Found this but did not help http://cache.freescale.com/files/32bit/doc/app_note/AN4381.pdf
 
Last edited:
I saw Paul did this in the pins_teensy.c

Code: 
// create a default PWM at the same 488.28 Hz as Arduino Uno
#if F_BUS == 48000000
#define DEFAULT_FTM_MOD (49152 - 1)
#define DEFAULT_FTM_PRESCALE 1
#else
#define DEFAULT_FTM_MOD (49152 - 1)
#define DEFAULT_FTM_PRESCALE 0
#endif

//void init_pins(void)
void _init_Teensyduino_internal_(void)
{
	init_pin_interrupts();

	//SIM_SCGC6 |= SIM_SCGC6_FTM0;	// TODO: use bitband for atomic read-mod-write
	//SIM_SCGC6 |= SIM_SCGC6_FTM1;
	FTM0_CNT = 0;
	FTM0_MOD = DEFAULT_FTM_MOD;
	FTM0_C0SC = 0x28; // MSnB:MSnA = 10, ELSnB:ELSnA = 10
	FTM0_C1SC = 0x28;
	FTM0_C2SC = 0x28;
	FTM0_C3SC = 0x28;
	FTM0_C4SC = 0x28;
	FTM0_C5SC = 0x28;
	FTM0_C6SC = 0x28;
	FTM0_C7SC = 0x28;
	FTM0_SC = FTM_SC_CLKS(1) | FTM_SC_PS(DEFAULT_FTM_PRESCALE);
	FTM1_CNT = 0;
	FTM1_MOD = DEFAULT_FTM_MOD;
	FTM1_C0SC = 0x28;
	FTM1_C1SC = 0x28;
	FTM1_SC = FTM_SC_CLKS(1) | FTM_SC_PS(DEFAULT_FTM_PRESCALE);
#if defined(__MK20DX256__)
	FTM2_CNT = 0;
	FTM2_MOD = DEFAULT_FTM_MOD;
	FTM2_C0SC = 0x28;
	FTM2_C1SC = 0x28;
	FTM2_SC = FTM_SC_CLKS(1) | FTM_SC_PS(DEFAULT_FTM_PRESCALE);
#endif

	analog_init();
	//delay(100); // TODO: this is not necessary, right?
	delay(4);
	usb_init();
}

Is this maybe an reason, I don't know. Paul or else please help.
 
Your code in reply #5 sets the timer for an external clock, but I don't see any lines that configure a pin. There may be other issues, but that's the one obvious thing I can see from only a quick look.
 
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