Sooner Competitive Robotics / Mbed 2 deprecated IEEE_14_Freescale

Important changes to repositories hosted on mbed.com

Mbed hosted mercurial repositories are deprecated and are due to be permanently deleted in July 2026.

To keep a copy of this software download the repository Zip archive or clone locally using Mercurial.

It is also possible to export all your personal repositories from the account settings page.

Dependencies:   mbed

Fork of IEEE_14_Freescale by IEEE 2014 Mbed

hcsr04.h@33:03b0b66038e1, 2014-03-23 (annotated)

Committer:
sswatek
Date:
Sun Mar 23 02:23:29 2014 +0000
Revision:
33:03b0b66038e1
Parent:
31:4ef53fbd6759 
able to move along the row of waves and find the gap

Who changed what in which revision?

UserRevisionLine numberNew contents of line
soonerbot 14:a30aa3b29a2e 1 // Primary Author: David Glover
soonerbot 14:a30aa3b29a2e 2 // March, 2012
soonerbot 14:a30aa3b29a2e 3 // ECE 510 Embedded Systems, Roy Kravitz
soonerbot 14:a30aa3b29a2e 4 //
soonerbot 14:a30aa3b29a2e 5 // HCSR04 ultrasonic sensor class using interrupts and allowing multiple instances.
soonerbot 15:b10859606504 6 // You can use the same trigger pin for multiple instances; the echo is received and
soonerbot 15:b10859606504 7 // measurement calculated based on the echo input alone. (when the echo signal goes high,
soonerbot 15:b10859606504 8 // the timer is started. When the echo signal goes low, the timer value in microseconds
soonerbot 15:b10859606504 9 // is saved as the length, and the timer is stopped and reset) Length calculation is done
soonerbot 15:b10859606504 10 // when the length is requested (either inches or centimeters).
soonerbot 14:a30aa3b29a2e 11
soonerbot 14:a30aa3b29a2e 12 #ifndef MBED_HCSR04_H
soonerbot 14:a30aa3b29a2e 13 #define MBED_HCSR04_H
soonerbot 14:a30aa3b29a2e 14
soonerbot 14:a30aa3b29a2e 15 //required to use mbed functions
soonerbot 14:a30aa3b29a2e 16 #include "mbed.h"
soonerbot 14:a30aa3b29a2e 17
soonerbot 14:a30aa3b29a2e 18 #define TRIGGER_DELAY 12 // length of trigger signal expected by HCSR04 sensor
sswatek 33:03b0b66038e1 19 #define INCHES_DIVISOR 139 //
soonerbot 14:a30aa3b29a2e 20 #define CM_DIVISOR 58
soonerbot 14:a30aa3b29a2e 21
soonerbot 14:a30aa3b29a2e 22 class hcsr04 {
soonerbot 14:a30aa3b29a2e 23
soonerbot 14:a30aa3b29a2e 24 private:
soonerbot 15:b10859606504 25 InterruptIn *_echo_int; // pin to receive echo signal; input
soonerbot 15:b10859606504 26 DigitalOut trigger_out; // pin to send the trigger signal; output
soonerbot 14:a30aa3b29a2e 27 Timer timer; // timer to track length of pulse
sswatek 31:4ef53fbd6759 28 volatile float value; // to store the last pulse length
soonerbot 14:a30aa3b29a2e 29
soonerbot 14:a30aa3b29a2e 30 public:
soonerbot 14:a30aa3b29a2e 31 bool measuring; // true while the echo signal is high (measurement in progress)
soonerbot 14:a30aa3b29a2e 32 hcsr04(PinName trigger, PinName echo) : trigger_out(trigger) { // _pass the names to the pin configuration
soonerbot 14:a30aa3b29a2e 33 //trigger_out = new DigitalOut( trigger );
soonerbot 15:b10859606504 34 _echo_int = new InterruptIn( echo ); // interrupts
soonerbot 15:b10859606504 35 _echo_int->rise(this, &hcsr04::timer_start); // when trigger is sent
soonerbot 15:b10859606504 36 _echo_int->fall(this, &hcsr04::calc_measurement); // when echo is received
soonerbot 14:a30aa3b29a2e 37 measuring = false;
soonerbot 14:a30aa3b29a2e 38 }
soonerbot 14:a30aa3b29a2e 39
soonerbot 14:a30aa3b29a2e 40 void calc_measurement() {
soonerbot 14:a30aa3b29a2e 41 value = timer.read_us();
soonerbot 14:a30aa3b29a2e 42 //value = timer.read_us() - timestart;
soonerbot 14:a30aa3b29a2e 43 timer.stop();
soonerbot 14:a30aa3b29a2e 44 timer.reset();
soonerbot 14:a30aa3b29a2e 45 measuring = false;
soonerbot 14:a30aa3b29a2e 46 }
soonerbot 14:a30aa3b29a2e 47
soonerbot 14:a30aa3b29a2e 48 void timer_start() {
sswatek 31:4ef53fbd6759 49 timer.reset();
sswatek 31:4ef53fbd6759 50 timer.start();
sswatek 31:4ef53fbd6759 51 //measuring = true;
soonerbot 14:a30aa3b29a2e 52 }
soonerbot 14:a30aa3b29a2e 53
soonerbot 14:a30aa3b29a2e 54 void trigger(void) {
soonerbot 14:a30aa3b29a2e 55 trigger_out.write(1); // start trigger signal
soonerbot 14:a30aa3b29a2e 56 wait_us(TRIGGER_DELAY);
soonerbot 14:a30aa3b29a2e 57 trigger_out.write(0); // end trigger signal
sswatek 31:4ef53fbd6759 58 measuring = true;
sswatek 31:4ef53fbd6759 59 timer.reset();
sswatek 31:4ef53fbd6759 60 timer.start();
soonerbot 14:a30aa3b29a2e 61 }
soonerbot 14:a30aa3b29a2e 62
soonerbot 14:a30aa3b29a2e 63 float inches() { // return distance in inches.
soonerbot 14:a30aa3b29a2e 64 return value / INCHES_DIVISOR;
soonerbot 14:a30aa3b29a2e 65 }
soonerbot 14:a30aa3b29a2e 66
soonerbot 14:a30aa3b29a2e 67 float cm() { // return distance in centimeters.
soonerbot 14:a30aa3b29a2e 68 return value / CM_DIVISOR;
soonerbot 14:a30aa3b29a2e 69 }
sswatek 31:4ef53fbd6759 70
soonerbot 14:a30aa3b29a2e 71
sswatek 31:4ef53fbd6759 72 //finds a stable distance value by taking count samples and putting them into buckets
sswatek 31:4ef53fbd6759 73 // of +-%10 that are moving averages
sswatek 31:4ef53fbd6759 74 // returns the distance in inches of a measurement with at least thresh results
sswatek 31:4ef53fbd6759 75 // returns -1 if no consensus was found and returns -2 if none of the samples were less than 19 inches away
sswatek 31:4ef53fbd6759 76 // which would indicate a "far" read
sswatek 31:4ef53fbd6759 77 float getStablePollAdv(int count, int thresh){
sswatek 31:4ef53fbd6759 78 float distBuckets[7] = {0,0,0,0,0,0,0};
sswatek 31:4ef53fbd6759 79 int bucketCount[7] = {0,0,0,0,0,0,0};
sswatek 31:4ef53fbd6759 80 for(int i=0;i<count;i++){
sswatek 31:4ef53fbd6759 81 trigger();
sswatek 31:4ef53fbd6759 82 while(measuring && timer.read_ms()<200);
sswatek 31:4ef53fbd6759 83 if(!measuring){
sswatek 31:4ef53fbd6759 84 //store value
sswatek 31:4ef53fbd6759 85 for(int j=0;j<7;j++){
sswatek 31:4ef53fbd6759 86 if(bucketCount[j]==0){
sswatek 31:4ef53fbd6759 87 //bucket empty, add to bucket
sswatek 31:4ef53fbd6759 88 distBuckets[j]=value;
sswatek 31:4ef53fbd6759 89 bucketCount[j]++;
sswatek 31:4ef53fbd6759 90 break;
sswatek 31:4ef53fbd6759 91 } else if(value > distBuckets[j]*0.9 && value < distBuckets[j]*1.1){
sswatek 31:4ef53fbd6759 92 //within range of center bucket, add
sswatek 31:4ef53fbd6759 93 distBuckets[j] = (distBuckets[j]*bucketCount[j]+value)/(bucketCount[j]+1);
sswatek 31:4ef53fbd6759 94 bucketCount[j]++;
sswatek 31:4ef53fbd6759 95 break;
sswatek 31:4ef53fbd6759 96 }
sswatek 31:4ef53fbd6759 97 }
sswatek 31:4ef53fbd6759 98 }
sswatek 31:4ef53fbd6759 99 }
sswatek 31:4ef53fbd6759 100 int maxBucket=0;
sswatek 31:4ef53fbd6759 101 int numBelowCutoff=0; // this is used to track if any values are below a cutoff
sswatek 31:4ef53fbd6759 102 const float cutoff=19.0 * INCHES_DIVISOR;
sswatek 31:4ef53fbd6759 103 if(distBuckets[0]<cutoff)
sswatek 31:4ef53fbd6759 104 numBelowCutoff += bucketCount[0];
sswatek 31:4ef53fbd6759 105 //DBGPRINT("Bucket #0 has %d at %f\r\n",bucketCount[0],distBuckets[0] / INCHES_DIVISOR);
sswatek 31:4ef53fbd6759 106 for(int i=1;i<7;i++){
sswatek 31:4ef53fbd6759 107 // cycling through the values to find the bucket with the most members
sswatek 31:4ef53fbd6759 108 if(distBuckets[i]<cutoff)
sswatek 31:4ef53fbd6759 109 numBelowCutoff += bucketCount[i];
sswatek 31:4ef53fbd6759 110 //DBGPRINT("Bucket #%d has %d at %f\r\n",i,bucketCount[i],distBuckets[i] / INCHES_DIVISOR);
sswatek 31:4ef53fbd6759 111 if(bucketCount[maxBucket]<bucketCount[i])
sswatek 31:4ef53fbd6759 112 maxBucket=i;
sswatek 31:4ef53fbd6759 113 }
sswatek 31:4ef53fbd6759 114 if(bucketCount[maxBucket]>=thresh){
sswatek 31:4ef53fbd6759 115 return distBuckets[maxBucket] / INCHES_DIVISOR;
sswatek 31:4ef53fbd6759 116 } else if(numBelowCutoff==0){
sswatek 31:4ef53fbd6759 117 return -2;
sswatek 31:4ef53fbd6759 118 }else{
sswatek 31:4ef53fbd6759 119 return -1;
sswatek 31:4ef53fbd6759 120 }
sswatek 31:4ef53fbd6759 121 }
sswatek 31:4ef53fbd6759 122
sswatek 31:4ef53fbd6759 123 // (15,8) seems to give good results, so this convienence function can be used for these defaults
sswatek 31:4ef53fbd6759 124 float getStablePoll(void){
sswatek 31:4ef53fbd6759 125 return getStablePollAdv(15,8);
sswatek 31:4ef53fbd6759 126 }
sswatek 31:4ef53fbd6759 127
soonerbot 15:b10859606504 128 /* void hscr04_main(void) { // Rohan's code
soonerbot 15:b10859606504 129 //trigger();
soonerbot 15:b10859606504 130 // delay
soonerbot 14:a30aa3b29a2e 131 while(measuring == false);
soonerbot 14:a30aa3b29a2e 132 // interrupts call timer_start() and calc_measurement()
soonerbot 14:a30aa3b29a2e 133 }
soonerbot 14:a30aa3b29a2e 134 */
soonerbot 14:a30aa3b29a2e 135
soonerbot 14:a30aa3b29a2e 136 };
soonerbot 14:a30aa3b29a2e 137
soonerbot 14:a30aa3b29a2e 138 #endif