/*
 This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
int right_echo_pin = 6;
int right_trigger_pin = 7;

int left_echo_pin = 11;
int left_trigger_pin = 12;

int right_ping_microseconds = 0;
int left_ping_microseconds = 0;
double sound_cm_per_microsecond_at_sea_level = 0.034029;
int count = 0;

void on(int pin){
  digitalWrite(pin, HIGH);}

void off(int pin){
  digitalWrite(pin, LOW);}

int ping(int trigger, int echo){
  int ping_time = 0;
  // turn off trigger
  off(trigger);
  delayMicroseconds(2);
  // turn on the trigger and leave it on long enough for the
  // sonar sensor to notice
  on(trigger);
  delayMicroseconds(10);
  off(trigger);
  ping_time = pulseIn(echo, HIGH);
  if(ping_time <= 0){
    ping_time = 3000;}
  // sonar needs some time to recover before pinging again,
  // so make sure it gets enough sleep right here.  50 milliseconds
  delay(50);
  return ping_time;}

void setup(){
  Serial.begin(9600);
  pinMode(right_echo_pin, INPUT);
  pinMode(right_trigger_pin, OUTPUT);
  pinMode(left_echo_pin, INPUT);
  pinMode(left_trigger_pin, OUTPUT);}

void loop(){
  right_ping_microseconds = ping(right_trigger_pin, right_echo_pin);
  left_ping_microseconds = ping(left_trigger_pin, left_echo_pin);
  // print out the pulse time
  Serial.print(right_ping_microseconds);
  Serial.print(" = right ping microseconds, ");
  Serial.print(left_ping_microseconds);
  Serial.print(" = left ping microseconds. #");
  Serial.println(count++);

  // wait so it's easier to read the serial monitor.
  // change delay to 0 for fullspeed.
  //  default is 333, which is about 1/3 of a second
  delay(333);}