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Dan-Q/README.txt

Created May 4, 2018
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GC591VV "You Can't Do It Alone!" geocache source code
This is the source code the the Arduinos powering my GC591VV "You Can't Do It Alone!" cache:
further details can be found at https://danq.me/2014/08/13/gc591vv/
synchronise_clocks.ino - this program sets the clock on the device to the date and time of
compilation: run it at the same time on both boxes to synchronise them
it_takes_two_cache.ino - this is the program that runs on both boxes when they're to be
deployed to the field; some constants need setting:
* SALT - needs to be set to a random number (the same for both boxes); this helps to prevent
cryptanalysis of the output given only one box
* SECOND_UNIT - needs to be set to true on the one box, false on the other
* TARGET_NORTH, TARGET_WEST - the Northings and Westings parts of the GZ of the actual cache
container, expressed as a long decimal
#include <LiquidCrystal.h>
#include <Wire.h>
#include <RTClib.h>
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
// initialize the real-time clock (DS1307 chip)
RTC_DS1307 RTC;
const int LIFESPAN = 900; // How many seconds does each code-cycle last. Default 900 (15 minutes).
const int EPOCH = 104; // Number of days before code-cycle completes and starts over. Default 104.
const long SALT = 17628435; // To avoid trivial cryptanalysis, a secret salt is added to the random seed.
const boolean SECOND_UNIT = false; // Is this device the second of the two units? "false" for unit A, "true" for unit B.
const unsigned long TARGET_NORTH = 5112123L; // 51° 12.123'
const unsigned long RNG_NORTH_MIN = 1000000L;
const unsigned long TARGET_WEST = 112123L; // 001° 12.123'
const unsigned long RNG_WEST_MIN = 100000L;
void setup() {
Wire.begin();
RTC.begin();
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
}
/* Given the current DateTime, returns the number of the current code-cycle:
* i.e. a number between 0 and 9983 (changing every 15 minutes throughout a
* 104-day cycle) [assuming default constant values].
*/
int code_cycle_number(DateTime now){
int day_count = now.unixtime() / 86400L;
// calculate code number
int code_number = ((day_count % EPOCH) * (24 * (3600 / LIFESPAN))) +
(now.hour() * (3600 / LIFESPAN)) +
(now.minute() / (LIFESPAN / 60));
return code_number;
}
/* Given the current DateTime, returns the number of whole seconds remaining
* in the current code-cycle: i.e. a number between 900 and 1 [assuming
* default constant values].
*/
int seconds_left_this_cycle(DateTime now){
int secs_left = LIFESPAN;
secs_left -= (now.minute() % 15) * 60;
secs_left -= now.second();
return secs_left;
}
/* Given a random seed (typically based on the current date and time) and a
* boolean - "true" if this is the "unit B" (the second of the two paired
* devices), "false" otherwise - returns a formatted string suitable for
* outputting to a single 16-character LCD screen layer (7 digits, one space,
* 8 digits [because longitude of the same precision potentially has one more
* digit]).
* Note that to avoid having to think about pointers, the THIRD parameter is
* the character array (string buffer) to be populated with the string, rather
* than this function truly returning a value.
*/
void partial_coordinates(int seed, boolean second_unit, char buf[]){
randomSeed(seed);
unsigned long rOffsetNorth = random(TARGET_NORTH - RNG_NORTH_MIN);
unsigned long rOffsetWest = random(TARGET_WEST - RNG_WEST_MIN);
unsigned long rNorth = rOffsetNorth + RNG_NORTH_MIN;
unsigned long rWest = rOffsetWest + RNG_WEST_MIN;
unsigned long rAlternateNorth = TARGET_NORTH - rNorth;
unsigned long rAlternateWest = TARGET_WEST - rWest;
if(second_unit){ // if we're the second unit, show the alternate coords
sprintf(buf, "%07lu %08lu", rAlternateNorth, rAlternateWest);
} else { // we're the first unit, show the regular coords
sprintf(buf, "%07lu %08lu", rNorth, rWest);
}
}
void loop() {
DateTime now = RTC.now();
int code_cycle = code_cycle_number(now);
int secs_left = seconds_left_this_cycle(now);
char line1[16], line2[16];
// print the cycle number and the number of seconds left this cycle
sprintf(line1, "Code %04d (%3ds)", code_cycle, secs_left);
lcd.setCursor(0, 0);
lcd.print(line1);
// print the partial coordinates
partial_coordinates(SALT + code_cycle, SECOND_UNIT, line2);
lcd.setCursor(0, 1);
lcd.print(line2);
// DEBUG: print the current datetime
//sprintf(line2, "%04d%02d%02d %02d%02d%02d", now.year(), now.month(), now.day(), now.hour(), now.minute(), now.second());
//lcd.setCursor(0, 1);
//lcd.print(line2);
delay(1000);
}
#include <LiquidCrystal.h>
#include <Wire.h>
#include <RTClib.h>
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
// initialize the real-time clock (DS1307 chip)
RTC_DS1307 RTC;
void setup() {
Wire.begin();
RTC.begin();
Serial.begin(9600);
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// set the DS1307 system clock to the date and time of compilation
RTC.adjust(DateTime(__DATE__, __TIME__));
lcd.setCursor(0, 0);
lcd.print(__DATE__);
lcd.setCursor(0, 1);
lcd.print(__TIME__);
}
void loop() {
delay(1000);
lcd.setCursor(0, 1);
Serial.println(RTC.now().unixtime());
lcd.print(RTC.now().unixtime());
}
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