salve a tutti, sto cercando di migliorare la resa di un hc-sr04 utilizzando un nuovo codice che ho trovato in linea che tra l'altro si chiama Better echo 
/* Ultrasonic distance sensor example - Better Version
Paul Carpenter, PC Services
26-Jan-2017
Update 4-Feb-2017 PC make variables more obvious
Update 13-May-2017 PC add half bit rounding to distance calculation
Uses HC-SR04 four pin ultrasonic sensor to continuously output distances
found when in range (every second).
Results WHEN valid output onto serial port at 115,200 baud
Both LEDs ON when program starts and any other time for no start of echo
received (probably bad wiring or faulty unit) on start up also serial port
error string
Lights RED Led when No Reading received or out of range
Lights Yellow LED when too close (less than 5 cm)
LEDs are connected via 330R or similar resistor other end of LED to GND
Works on principle sound travels at 343.2 m/s in dry STILL air at 20 deg C
So time per cm is 29.137529 micro seconds /cm
For round trip (there and back) 58.275058 micro seconds /cm
In order to reduce code size and execution time values are kept as integers
and factor of 58 to calculate distances
*/
/* Pin definitions */
#define echopin 9
#define trigpin 10
//#define redled 6
//#define yellowled 7
/* time between readings in ms
On Arduino Mega readings belown 20ms interval could
have residual echo issues */
#define INTERVAL 30
/* Scale factor round trip micro seconds per cm */
#define SCALE_CM 58
#define SCALE_CM_ROUND (SCALE_CM/2)
/* Timeout for distance sensing rather than 1 second in us */
#define MAX_ECHO 300000
#define MIN_ECHO (3 * SCALE_CM)
/* Timeout for start of ECHO pulse being received in us */
#define MAX_START_ECHO 1000
/* Limits for application ranges in cm */
#define MIN_RANGE 4
#define MAX_RANGE 500
#define MAX_ERROR 10
/* calculated distance in centimetres */
unsigned long distance;
unsigned int echotime;
unsigned long next_time, new_time;
/* Distance sensor function to get echo time
Note most ultrasonic distance sensors are only usable beyond 3 cm
So usable range is 3 * SCALE_CM to MAX_ECHO, therefore anything below
3 * SCALE_CM should be treated as error
Returns echo time in microseconds
Maximum MAX_ECHO
Minimum 3 * SCALE_CM (minimum usable)
error codes
Error 2 Echo HIGH before start
Error 1 Echo did not start
Error 0 NO ECHO (Timeout)
Timeout for measurements set by MAX_ECHO
*/
unsigned long GetEchoTime( )
{
unsigned long start_time;
unsigned long end_time;
/* check Echo if high return error */
if( digitalRead( echopin ) )
return( 2 );
/* note start time */
start_time = micros( );
/* send the trigger pulse */
digitalWrite( trigpin, HIGH );
delayMicroseconds( 10 );
digitalWrite( trigpin, LOW );
/* Set timeout for start of echo pulse */
end_time = start_time + MAX_START_ECHO;
/* check ECHO pin goes high within MAX_START_ECHO
if not return error of 1 */
while( !digitalRead( echopin ) )
if( micros( ) > end_time )
return( 1 );
/* Check for Length of echo occurred or timeout */
start_time = micros( );
end_time = start_time + MAX_ECHO;
while( digitalRead( echopin ) )
if( micros( ) > end_time )
break;
end_time = micros( );
/* Return time or timeout */
return( ( start_time < end_time ) ? end_time - start_time: 0 );
}
void setup( )
{
/* set time from reset */
next_time = INTERVAL;
Serial.begin( 115200 );
/* Configure pins and ensure trigger is OFF */
pinMode( trigpin, OUTPUT );
digitalWrite( trigpin, LOW );
pinMode( echopin, INPUT );
/* Configure LED drive and both LEDs On at start up */
//pinMode( redled, OUTPUT );
//pinMode( yellowled, OUTPUT );
//digitalWrite( redled, HIGH );
//digitalWrite( yellowled, HIGH );
/* Send signon message */
Serial.println( F( "PC Services - Better Range test" ) );
/* Do test reading to check if unit connected */
distance = GetEchoTime( );
if( distance > 0 && distance <= 10 )
{
Serial.println( F( "No unit found - Error = " ) );
Serial.println( distance );
}
}
void loop( )
{
new_time = millis( ); /* check if to run this time */
if( new_time >= next_time )
{
/* Turn LEDs Off */
// digitalWrite( redled, LOW );
// digitalWrite( yellowled, LOW );
/* Calculate distance */
echotime = GetEchoTime( );
/* only scale valid readings 0 is timeout or 1 is no echo
realistically minimum accurate or physical range is 3cm */
if( echotime > MAX_ERROR )
{
// Valid number covert to cm
distance = echotime;
distance += SCALE_CM_ROUND; // add in half bit rounding
distance /= SCALE_CM;
}
/* catch errors first */
if( echotime <= MAX_ERROR || distance > MAX_RANGE )
{
// digitalWrite( redled, HIGH ); // Range error too large
if( echotime > 0 && echotime <= MAX_ERROR )
// digitalWrite( yellowled, HIGH ); // Light 2nd LED error
Serial.println("MAX");
}
else
if( distance < MIN_RANGE )
// digitalWrite( yellowled, HIGH ); // Range too close
Serial.println("MIN");
else
Serial.println( int( distance ) ); // In range output distance
next_time = new_time + INTERVAL; // save next time to run
}
}
ammetto di non avere veramente capito a fondo il codice ma:
se punto il sensore su pareti distanti piu di 5 mt, perchè sul monitor seriale non ho mai la sritta MAX ? (se metto un ostacolo entro i 4 cm sul serial monitor ho la scritta MIN)
anni fa durante dei test con l'hc-sr04 , aggiungendo dei cilindri ai sensori, e con questo codice:
/*
* Ultrasonic Sensor HC-SR04 and Arduino Tutorial
*
* by Dejan Nedelkovski,
* www.HowToMechatronics.com
*
*/
// defines pins numbers
const int trigPin = 9;
const int echoPin = 10;
// defines variables
long duration;
int distance;
void setup() {
pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
pinMode(echoPin, INPUT); // Sets the echoPin as an Input
Serial.begin(9600); // Starts the serial communication
}
void loop() {
// Clears the trigPin
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
// Sets the trigPin on HIGH state for 10 micro seconds
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);
// Calculating the distance
distance= duration*0.034/2;
// Prints the distance on the Serial Monitor
Serial.print("Distance: ");
Serial.println(distance);
}
ho misurato fino a 7 metri.. (so che il datasheet del hc-sr04 dice max 5mt)
come posso modificare il primo codice per poter rendere valide misure sopra i sei metri?
grazie in anticipo!!