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#define trigPin 23                                  // Pin 23 trigger output
#define echoPin 22                                    // Pin 22 Echo input
#define echo_int 0                                    // Interrupt id for echo pulse

#define TIMER_US 80                                   // 80 uS timer duration 
#define TICK_COUNTS 4000                              // 200 mS worth of timer ticks

volatile long echo_start = 0;                         // Records start of echo pulse 
volatile long echo_end = 0;                           // Records end of echo pulse
volatile long echo_duration = 0;                      // Duration - difference between end and start
volatile int trigger_time_count = 0;                  // Count down counter to trigger pulse time
volatile long range_flasher_counter = 0;              // Count down counter for flashing distance LED

hw_timer_t * Timer1 = NULL;
portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;
 
// --------------------------
// timerIsr() 50uS second interrupt ISR()
// Called every time the hardware timer 1 times out.
// --------------------------

void IRAM_ATTR timerIsr() {
  portENTER_CRITICAL_ISR(&timerMux);
  trigger_pulse();    
  portEXIT_CRITICAL_ISR(&timerMux);
 
}

// ----------------------------------
// setup() routine called first.
// A one time routine executed at power up or reset time.
// Used to initialise hardware.
// ----------------------------------
void setup() 
{
  pinMode(trigPin, OUTPUT);                           // Trigger pin set to output
  pinMode(echoPin, INPUT);                            // Echo pin set to input
  
  Timer1 = timerBegin(0, TIMER_US, true);                        // Initialise timer 1
  timerAttachInterrupt(Timer1, &timerIsr, true);                 // Attach interrupt to the timer service routine 
  timerAttachInterrupt(echo_int, echo_interrupt, CHANGE);  // Attach interrupt to the sensor echo input
  Serial.begin (9600);                                // Initialise the serial monitor output
}

// ----------------------------------
// loop() Runs continuously in a loop.
// This is the background routine where most of the processing usualy takes place.
// Non time critical tasks should be run from here.
// ----------------------------------
void loop()
{
    Serial.println(echo_duration / 58);               // Print the distance in centimeters
    delay(100);                                       // every 100 mS
}


// --------------------------
// trigger_pulse() called every 10 uS to schedule trigger pulses.
// Generates a pulse one timer tick long.
// Minimum trigger pulse width for the HC-SR04 is 10 us. This system
// delivers a 10 uS pulse.
// --------------------------
void trigger_pulse()
{
      static volatile int state = 0;                 // State machine variable

      if (!(--trigger_time_count))                   // Count to 200mS
      {                                              // Time out - Initiate trigger pulse
         trigger_time_count = TICK_COUNTS;           // Reload
         state = 1;                                  // Changing to state 1 initiates a pulse
      }
    
      switch(state)                                  // State machine handles delivery of trigger pulse
      {
        case 0:                                      // Normal state does nothing
            break;
        
        case 1:                                      // Initiate pulse
           digitalWrite(trigPin, HIGH);              // Set the trigger output high
           state = 2;                                // and set state to 2
           break;
        
        case 2:                                      // Complete the pulse
        default:      
           digitalWrite(trigPin, LOW);               // Set the trigger output low
           state = 0;                                // and return state to normal 0
           break;
     }
}

// --------------------------
// echo_interrupt() External interrupt from HC-SR04 echo signal. 
// Called every time the echo signal changes state.
//
// Note: this routine does not handle the case where the timer
//       counter overflows which will result in the occassional error.
// --------------------------
void echo_interrupt()
{
  switch (digitalRead(echoPin))                     // Test to see if the signal is high or low
  {
    case HIGH:                                      // High so must be the start of the echo pulse
      echo_end = 0;                                 // Clear the end time
      echo_start = micros();                        // Save the start time
      break;
      
    case LOW:                                       // Low so must be the end of hte echo pulse
      echo_end = micros();                          // Save the end time
      echo_duration = echo_end - echo_start;        // Calculate the pulse duration
      break;
  }
}

// --------------------------
// distance_flasher() Called from the timer 1 timerIsr service routine.
// Flashes the onboard LED at a rate inversely proportional
// to distance. The closer it gets the higher the frequency.
// --------------------------
void distance_flasher()
{
      if (--range_flasher_counter <= 0)                // Decrement and test the flash timer
      {                                                // Flash timer time out
         if (echo_duration < 25000)                    // If the echo duration is within limits
         {
           range_flasher_counter = echo_duration * 2;  // Reload the timer with the current echo duration
         }
         else
         {
           range_flasher_counter = 25000;              // If out of range use a default
         }

      }
}

Code: Select all

ets Jun  8 2016 00:22:57

rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:2
load:0x3fff0030,len:1324
ho 0 tail 12 room 4
load:0x40078000,len:13480
ho 0 tail 12 room 4
load:0x40080400,len:3604
entry 0x400805f0
Guru Meditation Error: Core  1 panic'ed (LoadProhibited). Exception was unhandled.

Core  1 register dump:
PC      : 0x400d15ef  PS      : 0x00060d30  A0      : 0x800d1064  A1      : 0x3ffb27d0  
A2      : 0x00000000  A3      : 0x400d0fdc  A4      : 0x00000001  A5      : 0x3ffbdb70  
A6      : 0x00000000  A7      : 0x003fffff  A8      : 0x800d162c  A9      : 0x3ffb27a0  
A10     : 0x00000000  A11     : 0x00000000  A12     : 0x40081100  A13     : 0x3ffb8a88  
A14     : 0x00000000  A15     : 0x3ffc1228  SAR     : 0x00000020  EXCCAUSE: 0x0000001c  
EXCVADDR: 0x00000001  LBEG    : 0x40085c18  LEND    : 0x40085c23  LCOUNT  : 0xffffffff  


Backtrace:0x400d15ec:0x3ffb27d00x400d1061:0x3ffb27f0 0x400d1d26:0x3ffb2820 




ELF file SHA256: 0000000000000000