Modified Sonar code with the addition of the Modern Devices LCD117

Here’s the new sonar code with temp compensation and the addition of the Modern Devices LCD117. All of the references to the LCD library (#include <LiquidCrystal.h>) are gone and the “SoftwareSerial” header file is referenced instead (#include <SoftwareSerial.h>).

Additionally, notice I had to add a function to display floating point numbers. I visited Peter H. Anderson’s site for directions to display floating point numbers on the LCD117. (Peter is the designer of the LCD117).

http://phanderson.com/arduino/arduino_display.html

Note: I’ll likely take temperature compensation out to save memory when we move the code to the rover. I don’t think it’s really necessary for object avoidance in a fast moving robot. However, it was beneficial for the grandson to learn how temperature affects the speed of sound in air.

——————————————————————————-

// Sonar with temp compensated ping and addtiion of LCD117

// Jim Winburn > http://www.apphipania.com

#include <SoftwareSerial.h>

//constants

#define rxPin 4 // rxPin is immaterial – not used

#define txPin 14 // pin 14 is analog pin 0, use a 3 wire servo cable , see Reference pinMode

SoftwareSerial mySerial = SoftwareSerial(rxPin, txPin);

const float sensor_gap =0.2;

const int pingPin = 7; //ping sensor

const int tempPin = 1; //TMP36 temperature sensor

const float supplyv = 5.0; //suply voltage

const float ts_offset = 3.86515625; //TM136 calibration offset

const int ts_multi = 30; // TM136 temp multi (calibration)

const float cm_to_in = 0.3937008; //convert cm to inches

//variables

float current_temp;

float duration, inches, cm, temp_f, comp_duration, comp_inches;

//——————————————————–

void setup()

{

// establish variables for duration of the ping,

// and the distance result in inches and centimeters:

pinMode(txPin, OUTPUT);

mySerial.begin(9600); // 9600 baud is chip comm speed

mySerial.print(“?G420″); // set display geometry, 4 x 20 characters in this case

delay(500); // pause to allow LCD EEPROM to program

mySerial.print(“?Bff”); // set backlight to ff hex, maximum brightness

delay(1000); // pause to allow LCD EEPROM to program

mySerial.print(“?s6″); // set tabs to six spaces

delay(1000); // pause to allow LCD EEPROM to program

mySerial.print(“?f”); // clear the LCD

delay(10);

mySerial.print(“?x00?y0″); // cursor to first character of line 0

delay(10);

mySerial.print(“Distance to object:”);

}

//————————————————————-

void loop()

{

// get current temp

current_temp = get_temp();

// measure distance

float duration = measure_distance();

// convert the time into a distance in inches

inches = microsecondsToInches(duration);

// adjust speed of sound by temp

//mpcm = microseconds_per_cm();

// adjust duration in cm by temp and sensor offset

comp_duration = microseconds_to_cm(duration);

// convert the time into an adjusted distance in inches

comp_inches = (comp_duration * cm_to_in); // cm to inches

//—————————————

mySerial.print(“?x00?y1″); // cursor to first character of line 1

mySerial.print(” “);

mySerial.print(“?x00?y1″); // cursor to first character of line 1

print_float(inches,2); // print var in floating point with # decimal points

mySerial.print(“?x07?y1″); // cursor to first character of line 1

mySerial.print(” Inches”);

//—————————————-

mySerial.print(“?x00?y2″); // cursor to first character of line 2

mySerial.print(” “);

mySerial.print(“?x00?y2″); // cursor to first character of line 2

temp_f = current_temp * 9/5 + 32; //convert temp in c to f

print_float(temp_f,2); // print var in floating point with # decimal points

mySerial.print(“?x07?y2″); // cursor to first character of line 2

mySerial.print(” Deg F”);

//——————————————-

mySerial.print(“?x00?y3″); // cursor to first character of line 3

mySerial.print(” “);

mySerial.print(“?x00?y3″); // cursor to first character of line 3

print_float(comp_inches,2); // print var in floating point with # decimal points

mySerial.print(“?x07?y3″); // cursor to first character of line 3

mySerial.print(” Comp Inches”);

delay(500);

}

//———-functions—————–

float microsecondsToInches(float microseconds)

{

// According to Parallax’s datasheet for the PING))), there are

// 73.746 microseconds per inch (i.e. sound travels at 1130 feet per

// second). This gives the distance travelled by the ping, outbound

// and return, so we divide by 2 to get the distance of the obstacle.

// See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf

return microseconds / 73.746 / 2;

}

//———————————————–

float get_temp() //return filtered temp in c

{

// apply smoothing filter

const int numReadings = 10;

int readings[numReadings]; // number of samples from temp sensor

int index = 0; // index of the current reading

int total = 0; // running total

int average = 0; // average

// initialize all the temp readings to 0:

for (int thisReading = 0; thisReading < numReadings; thisReading++)

{

readings[thisReading] = 0;

// apply filter and get current temp

total= total – readings[index];

// read from the sensor:

readings[index] = analogRead(tempPin);

// add the reading to the total:

total= total + readings[index];

// advance to the next position in the array:

index = index + 1;

// if we’re at the end of the array…

if (index >= numReadings)

{

// …wrap around to the beginning:

index = 0;

// calculate the average:

average = total / numReadings;

}

}

return average * supplyv * ts_multi /1024 + ts_offset; //tempc ;

}

//————————————————————–

const float microseconds_per_cm()

{

return 1/ ((331.5 +(0.6 * current_temp)) /10000);

}

//—————————————————————

const float sensor_offset()

{

return sensor_gap * microseconds_per_cm() * 2;

}

//—————————————————————

const float microseconds_to_cm(const unsigned long microseconds)

{

const float net_distance = microseconds-sensor_offset();

return net_distance/ microseconds_per_cm()/2;

}

//—————————————————————-

const unsigned long measure_distance()

{

// The PING))) is triggered by a HIGH pulse of 2 or more microseconds.

// Give a short LOW pulse beforehand to ensure a clean HIGH pulse:

pinMode(pingPin, OUTPUT);

digitalWrite(pingPin, LOW);

delayMicroseconds(2);

digitalWrite(pingPin, HIGH);

delayMicroseconds(5);

digitalWrite(pingPin, LOW);

// The same pin is used to read the signal from the PING))): a HIGH

// pulse whose duration is the time (in microseconds) from the sending

// of the ping to the reception of its echo off of an object.

pinMode(pingPin, INPUT);

// get return time duration

return pulseIn(pingPin, HIGH);

}

//—————————————————————————-

void print_float(float f, int num_digits)

{

int f_int;

int pows_of_ten[4] = {1, 10, 100, 1000};

int multiplier, whole, fract, d, n;

multiplier = pows_of_ten[num_digits];

if (f < 0.0)

{

f = -f;

mySerial.print(“-”);

}

whole = (int) f;

fract = (int) (multiplier * (f – (float)whole));

mySerial.print(whole);

mySerial.print(“.”);

for (n=num_digits-1; n>=0; n–) // print each digit with no leading zero suppression

{

d = fract / pows_of_ten[n];

mySerial.print(d);

fract = fract % pows_of_ten[n];

}

}