File content as of revision 38:8efacce315ae:

#include "IMD.h"
#include <math.h>
#include "pinmap.h"


const float ZERO_HZ_TIMEOUT = 0.21;     // Time (sec) that must pass without an edge to call it 0 Hz, set to greater than the longest expected pulse width
const float EXTRA = 0.02;               // Margin on the IMD PWM limits

const uint32_t PCLK = 24000000;         // Timer counting clock = 24Mhz
const uint32_t TIMEOUT_TICKS = PCLK*ZERO_HZ_TIMEOUT;    // Zeroing timeout in clock ticks = seconds * PCLK

static IMD* instance[4] = { 0 };        // Access member from static frame, one IMD permitted per timer module (4 total IMD objects)

// Interrupt functions, must be static context
void tim0_IRQ() {    
    if (LPC_TIM0->IR & (1<<4|1<<5)) instance[0]->edgeIRQ();     // Capture pin interrupt
    if (LPC_TIM0->IR & 1) instance[0]->zeroIRQ();               // MR0 interrupt
    LPC_TIM0->IR=0x3F;        // Clear interrupt flags
}
void tim1_IRQ() {
    if (LPC_TIM1->IR & (1<<4|1<<5)) instance[1]->edgeIRQ();
    if (LPC_TIM1->IR & 1) instance[1]->zeroIRQ();
    LPC_TIM1->IR=0x3F;        // Clear interrupt flags
}
void tim2_IRQ() {
    if (LPC_TIM2->IR & (1<<4|1<<5)) instance[2]->edgeIRQ();
    if (LPC_TIM2->IR & 1) instance[2]->zeroIRQ();
    LPC_TIM2->IR=0x3F;        // Clear interrupt flags
}
void tim3_IRQ() {
    if (LPC_TIM3->IR & (1<<4|1<<5)) instance[3]->edgeIRQ();
    if (LPC_TIM3->IR & 1) instance[3]->zeroIRQ();
    LPC_TIM3->IR=0x3F;        // Clear interrupt flags
}

IMD::IMD(PinName _pin) {
    // Setup the timer/pin access variables
    if (_pin == P1_26) {          // CAP0.0
        timer=0;
        pin=0;
        timerBase=LPC_TIM0;
    } else if (_pin == P1_27) {   // CAP0.1
        timer=0;
        pin=1;
        timerBase=LPC_TIM0;
    } else if (_pin == P1_18) {   // CAP1.0
        timer=1;
        pin=0;
        timerBase=LPC_TIM1;
    } else if (_pin == P1_19) {   // CAP1.1
        timer=1;
        pin=1;
        timerBase=LPC_TIM1;
    } else if (_pin == P0_4) {    // CAP2.0
        timer=2;
        pin=0;
        timerBase=LPC_TIM2;
    } else if (_pin == P0_5) {    // CAP2.1
        timer=2;
        pin=1;
        timerBase=LPC_TIM2;
    } else if (_pin == P0_23) {   // CAP3.0
        timer=3;
        pin=0;
        timerBase=LPC_TIM3;
    } else if (_pin == P0_24) {   // CAP3.1
        timer=3;
        pin=1;
        timerBase=LPC_TIM3;
    } else {                        // Invalid pin
        timerBase=0;
        pin=0;
        timer=0;
        return;
    }
    
    instance[timer] = this;
    first = true;
    
    startTime = 0;
    widthTicks = 0;                 // Zero low, so that duty = 0/1 = 0%
    periodTicks = 1;
    
    // Enable power and set pclk at 24Mhz
    if (timer==0) { 
        LPC_SC->PCONP |= (1<<1);
        LPC_SC->PCLKSEL0 &= ~(3<<2);
    } if (timer==1) { 
        LPC_SC->PCONP |= (1<<2);
        LPC_SC->PCLKSEL0 &= ~(3<<4);
    } if (timer==2) { 
        LPC_SC->PCONP |= (1<<22);
        LPC_SC->PCLKSEL1 &= ~(3<<12);
    } if (timer==3) { 
        LPC_SC->PCONP |= (1<<23);
        LPC_SC->PCLKSEL1 &= ~(3<<14);
    }
    
    pin_function(_pin, 3);      // Capture input
    pin_mode(_pin, PullDown);   // Pull-down

    timerBase->TCR=2;       // Stop counter and hold at 0, for configuration
    timerBase->IR=0x3F;     // Clear any interrupt flags
    timerBase->CTCR=0;      // Use pclk, not external pin
    timerBase->PR=0;        // No prescale value, clock at full pclk=24Mhz
    timerBase->EMR=0;       // Do not use external match pins
    
    if (timer == 0) NVIC_SetVector(TIMER0_IRQn, (uint32_t)&tim0_IRQ);    // Set irq handler for timer0
    if (timer == 1) NVIC_SetVector(TIMER1_IRQn, (uint32_t)&tim1_IRQ);    // Set irq handler for timer1
    if (timer == 2) NVIC_SetVector(TIMER2_IRQn, (uint32_t)&tim2_IRQ);    // Set irq handler for timer2
    if (timer == 3) NVIC_SetVector(TIMER3_IRQn, (uint32_t)&tim3_IRQ);    // Set irq handler for timer3

    NVIC_EnableIRQ((IRQn_Type)(timer+1));
    NVIC_SetPriority((IRQn_Type)(timer+1), 0);      // Highest priority (default)
    
    timerBase->CCR = pin?5<<3:5;                    // Generate interrupt on rising edge of capture pin
    timerBase->MCR = 1;                             // Interrupt on MR0 to establish the zero speed timeout
    zeroIRQ();                                      // Zero the values
    timerBase->TCR = 1;                             // Start counting, GO!
}

void IMD::edgeIRQ() {
    bool rising = pin?timerBase->CCR&(1<<3):timerBase->CCR&1;
    uint32_t capTime = pin?timerBase->CR1:timerBase->CR0;   // Get the time of the capture event
    timerBase->MR0 = capTime + TIMEOUT_TICKS;               // Move the zero timeout ahead
    
    // Special case - on first pulse after a timeout or on startup == Period cannot be calculated
    //    so set startTime such that periodTicks remains unchanged from its zero state (periodTicks=1)
    if (first) {
        first = false;
        startTime = capTime - 1;   
    }
    if (rising) {
        periodTicks = capTime - startTime;  // Get the period on Rising edge
        startTime = capTime;                // Set the start of the next pulse
    } else {
        widthTicks = capTime - startTime;   // Get the pulse width on Falling edge   
    }
    
    // Switch interrupt types to capture the next edge
    if (rising) timerBase->CCR = pin?6<<3:6;
    else        timerBase->CCR = pin?5<<3:5;
}

void IMD::zeroIRQ() {
    periodTicks = 1;
    first = true;           // Reset the first edge detection case
    
    bool rising = pin?timerBase->CCR&(1<<3):timerBase->CCR&1;
    // Timeout occurred after FALLING edge, RISING edge never happened
    if (rising) {
        widthTicks = 0;     // Signal is low = 0/1 = 0% duty
    } else {
        widthTicks = 1;     // Signal is high = 1/1 = 100% duty   
    }
}
float IMD::frequency() {
    // Handle the case where we want to say 0Hz not infinity Hz
    if (periodTicks == 1 || periodTicks == 0) return 0;
    else return (float)(PCLK)/(float)(periodTicks);
}
float IMD::duty() {
    return (float)(widthTicks)/(float)(periodTicks);
}

char IMD::status() {
    float freq = frequency();
    if (freq == 0)                      return OFF;         // IMD off
    else if (05 < freq && freq <= 15)   return NORMAL;      // 10Hz normal mode
    else if (15 < freq && freq <= 25)   return UNDERVOLT;   // 20Hz undervoltage mode
    else if (25 < freq && freq <= 35)   return SPEEDSTART;  // 30Hz speed start mode
    else if (35 < freq && freq <= 45)   return ERROR;       // 40Hz IMD error
    else if (45 < freq && freq <= 55)   return GROUNDERR;   // 50Hz Ground error
    else return INVALID;                                    // Invalid
}

float IMD::resistance() {
    char stat = status();
    float dut = duty();
    
    // In normal or undervoltage mode, where Rf is available
    if (stat == NORMAL || stat == UNDERVOLT) {
        if (0.05-EXTRA <= dut && dut <= 0.95+EXTRA) {
            if (dut > 0.95) dut = 0.95;     // Ceiling
            if (dut < 0.05) dut = 0.05;     // Floor so it doesnt mess up the equation below
            float rf = (0.9*1200e3/(dut-0.05)) - 1200e3;
            if (rf < 1000) rf = 0;          // Floor to hit 0
            if (rf > 50e6) rf = 50e6;       // Ceil to stay at 50e6
            return rf;
        }
        else return NAN;
    }
    // In speed start, where only good/bad estimate is available
    if (stat == SPEEDSTART) {
        if (0.05-EXTRA <= dut && dut <= 0.10+EXTRA)       return 50e6;        // Good
        else if (0.90-EXTRA <= dut && dut <= 0.95+EXTRA)  return 0;           // Bad
        else return NAN;
    }
    return NAN;     // Measurement not available in this mode
}