elapsedTime

Overview

The elapsedTime utilities (elapsedMicros, elapsedMillis, elapsedSeconds) provide convenient wrappers to measure time intervals using the Timer class as a backend. They replicate the familiar API from PJRC’s Arduino elapsedMillis/elapsedMicros, adapted for TM4C1294XL and TivaWare.

These classes allow precise tracking of microseconds, milliseconds, and seconds without using interrupts or blocking loops.

Header-only library Micro / Milli / Second precision

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Features

• Lightweight, header-only implementation.
• Uses your configured Timer instance for accurate hardware timing.
• Compatible with both 32-bit and 64-bit timers.
• Implicit conversion to numeric types for easy comparison or arithmetic.
• Supports addition, subtraction, and assignment operations for intuitive usage.

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Basic Usage

1. Create a Timer object and call begin() before using the elapsed classes.

2. For each task you want to time, create a separate elapsedMicros, elapsedMillis, or elapsedSeconds object, depending on the required precision.

3. In your main loop, check if the elapsed time exceeds your threshold
   (for example, if (emillis >= 1000)).

4. If the condition is met, perform the task and reset the counter by assigning zero (emillis = 0;).

#include "timerLib.h"
#include "elapsedTime.h"


#define LED_PORT GPIO_PORTN_BASE
#define LED_PIN GPIO_PIN_1

Timer timer;


int main(void)
{
    uint32_t sysclk = SysCtlClockFreqSet(
    SYSCTL_XTAL_25MHZ | SYSCTL_OSC_MAIN |
    SYSCTL_USE_PLL | SYSCTL_CFG_VCO_480, 120000000);


    timer.begin(sysclk, TIMER0_BASE);


    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPION);
    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_GPION));
    GPIOPinTypeGPIOOutput(LED_PORT, LED_PIN);


    elapsedMillis blink(timer);
    elapsedSeconds log(timer);


    bool led = false;


    while (1) {
    if (blink >= 500) { // Toggle LED every 500 ms
            led = !led;
            GPIOPinWrite(LED_PORT, LED_PIN, led ? LED_PIN : 0);
            blink = 0;
        }

    if (log >= 2) { // Print every 2 seconds
        printf("%llu us, %llu ms, %llu s\n",
        (uint64_t)elapsedMicros(timer),
        (uint64_t)elapsedMillis(timer),
        (uint64_t)elapsedSeconds(timer));
        log = 0;
        }
    }
}

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Classes Summary

elapsedMicros

Tracks elapsed microseconds since creation or last reset.

explicit elapsedMicros(Timer& timer);
operator uint64_t() const;

Example:

elapsedMicros mu(timer);
if (mu >= 100) { // 100 microseconds
    mu = 0;
}

elapsedMillis

Tracks elapsed milliseconds since creation or last reset.

explicit elapsedMillis(Timer& timer);
operator uint64_t() const;

Example:

elapsedMillis ms(timer);
if (ms >= 500) { // 0.5 second
    toggleLED();
    ms = 0;
}

elapsedSeconds

Tracks elapsed seconds since creation or last reset.

explicit elapsedSeconds(Timer& timer);
operator uint64_t() const;

Example:

elapsedSeconds sec(timer);
if (sec >= 5) {
    printf("5 seconds passed!\n");
    sec = 0;
}

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Operator Support

Each class supports these operations:

Operation	Description
=	Resets timer offset to specific value.
+=, -=	Adjusts internal offset (forward/backward).
+, -	Returns a new adjusted copy.
Implicit conversion to uint64_t	Returns elapsed time.

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Example: LED Heartbeat + Sensor Update

#include "timerLib.h"
#include "elapsedTime.h"

#define LED_PORT GPIO_PORTN_BASE
#define LED_PIN  GPIO_PIN_1

Timer timer;

int main(void)
{
    uint32_t sysclk = SysCtlClockFreqSet(
        SYSCTL_XTAL_25MHZ | SYSCTL_OSC_MAIN |
        SYSCTL_USE_PLL | SYSCTL_CFG_VCO_480, 120000000);

    timer.begin(sysclk, TIMER0_BASE);

    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPION);
    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_GPION));
    GPIOPinTypeGPIOOutput(LED_PORT, LED_PIN);

    elapsedMillis blink(timer);
    elapsedSeconds log(timer);

    bool led = false;

    while (1) {
        if (blink >= 500) { // Toggle LED every 500 ms
            led = !led;
            GPIOPinWrite(LED_PORT, LED_PIN, led ? LED_PIN : 0);
            blink = 0;
        }

        if (log >= 2) { // Print every 2 seconds
            printf("%llu us, %llu ms, %llu s\n",
                   (uint64_t)elapsedMicros(timer),
                   (uint64_t)elapsedMillis(timer),
                   (uint64_t)elapsedSeconds(timer));
            log = 0;
        }
    }
}

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Integration Notes

• Always create at least one Timer instance and call begin() before using elapsed classes.
• Each elapsed instance internally holds a pointer to a Timer backend.
• Multiple elapsed instances can share the same timer for synchronized measurements.
• Precision depends on timer resolution (microseconds for 120 MHz clock ≈ 1 µs per tick).

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Dependencies

• timerLib.h
• driverlib/sysctl.h
• driverlib/timer.h

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License and Credits

Developed for ECE3849 — Real-Time Embedded Systems. Based on PJRC’s open elapsedMillis API, rewritten for TivaWare.

Author: Edwin R. Version 1.0