Frequency counting empty serial monitor

[speed07 1]

Hi all,

I have recently found a sketch in arduino forum for frequency counting, which I tried running in MSP432 with energia and MSP430 with energia sketch on Code composer studio. The sketch basically counts the frequency using interrupts and prints the frequency on serial monitor but serial monitor is empty while running the program,.The sketch is as shown below,

 

// Frequency counter sketch, for measuring frequencies low enough to execute an interrupt for each cycle

// Connect the frequency source to the INT0 pin (digital pin 2 on an Arduino Uno)

 

volatile unsigned long firstPulseTime;

volatile unsigned long lastPulseTime;

volatile unsigned long numPulses;

 

void isr()

{

 unsigned long now = micros();

 if (numPulses == 1)

 {

   firstPulseTime = now;

 }

 else

 {

   lastPulseTime = now;

 }

 ++numPulses;

}

 

void setup()

{

 Serial.begin(115200);    // this is here so that we can print the result

 pinMode(3, OUTPUT);     // put a PWM signal on pin 3, then we can connect pin 3 to pin 2 to test the counter

 analogWrite(3, 128);

}

 

// Measure the frequency over the specified sample time in milliseconds, returning the frequency in Hz

float readFrequency(unsigned int sampleTime)

{

 numPulses = 0;                      // prime the system to start a new reading

 attachInterrupt(0, isr, RISING);    // enable the interrupt

 delay(sampleTime);

 detachInterrupt(0);

 return (numPulses < 3) ? 0 : (1000000.0 * (float)(numPulses - 2))/(float)(lastPulseTime - firstPulseTime);

}

 

void loop()

{

 float freq = readFrequency(1000);

 Serial.println(freq);

 delay(1000);

}

[LiviuM 43]

Where are you defining the input (counter) pin?

[LiviuM 43]

LE Found it, the pins default to inputs:

 

LaunchPad pins default to inputs, so they don

[speed07 1]

I redefined the interrupt pin and now the serial monitor shows output as 0.00 but it should be showing 490Hz (PWM frequency), where have I gone wrong  ?

[NurseBob 111]

I don't use Energia all that much, but doesn't delay() put the mcu into LPM4 - no timers, only hdwe interrupts? Since the frequency counter requires the timers, you might consider looking there...

[speed07 1]

Btw the the serial monitor is outputting 490 after explicitly declaring the interrupt pin as input in void setup().Thanks for the tip,  LiviuM.  

// Frequency counter sketch, for measuring frequencies low enough to execute an interrupt for each cycle
// Connect the frequency source to the INT0 pin (digital pin 2 on an Arduino Uno)

volatile unsigned long firstPulseTime;
volatile unsigned long lastPulseTime;
volatile unsigned long numPulses;

void isr()
{
 unsigned long now = micros();
 if (numPulses == 1)
 {
   firstPulseTime = now;
 }
 else
 {
   lastPulseTime = now;
 }
 ++numPulses;
}

void setup()
{
 Serial.begin(115200);    // this is here so that we can print the result
 pinMode(4, OUTPUT);     // put a PWM signal on pin 3, then we can connect pin 3 to pin 2 to test the counter
analogWrite(4,128);
 pinMode(11,INPUT);
}

// Measure the frequency over the specified sample time in milliseconds, returning the frequency in Hz
float readFrequency(unsigned int sampleTime)
{
 numPulses = 0;                      // prime the system to start a new reading
 attachInterrupt(11, isr, RISING);    // enable the interrupt
 delay(sampleTime);
 detachInterrupt(0);
 return (numPulses < 3) ? 0 : (1000000.0 * (float)(numPulses - 2))/(float)(lastPulseTime - firstPulseTime);
}

void loop()
{
 float freq = readFrequency(1000);
 Serial.println(freq);
 
 delay(1000);
}