{"id":5579,"date":"2019-03-09T17:12:06","date_gmt":"2019-03-09T22:12:06","guid":{"rendered":"https:\/\/dronebotworkshop.com\/?p=5579"},"modified":"2023-04-12T11:45:57","modified_gmt":"2023-04-12T15:45:57","slug":"real-time-clock-arduino","status":"publish","type":"post","link":"https:\/\/dronebotworkshop.com\/real-time-clock-arduino\/","title":{"rendered":"Using a Real Time Clock with Arduino"},"content":{"rendered":"\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-9571 size-full alignnone\" title=\"Download PDF\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2023\/04\/dbws-pdfdown.png?resize=64%2C64&#038;ssl=1\" alt=\"Download PDF\" width=\"64\" height=\"64\" data-recalc-dims=\"1\" \/> <a href=\"#Parts_List\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-9563 size-full\" title=\"Parts List\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2023\/04\/dbws-parts.png?resize=64%2C64&#038;ssl=1\" alt=\"Parts List\" width=\"64\" height=\"64\" data-recalc-dims=\"1\" \/><\/a> <a href=\"https:\/\/youtu.be\/lyvoOEO-Ncg\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-9565 size-full\" title=\"View on YouTube\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2023\/04\/dbws-youtube.png?resize=64%2C64&#038;ssl=1\" alt=\"View on YouTube\" width=\"64\" height=\"64\" data-recalc-dims=\"1\" \/><\/a> <a href=\"https:\/\/s3.amazonaws.com\/download.dronebotworkshop.com\/Real+Time+Clock+-+DroneBot+Workshop.zip\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-9569 size-full\" title=\"Download Code\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2023\/04\/dbws-codedown.png?resize=64%2C64&#038;ssl=1\" alt=\"Download Code\" width=\"64\" height=\"64\" data-recalc-dims=\"1\" \/><\/a><\/p>\n<h2><span style=\"font-weight: 400;\">Introduction<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">The Arduino is an amazing device. It\u2019s useful for prototyping and can also be used to construct a complete project. It has an analog to digital converters (ADC), digital I\/O pins, it handles interrupts and it can communicate via a serial port, SPI, and I2C.<\/span><\/p>\n<div class=\"youtube-player\" data-id=\"lyvoOEO-Ncg\"><\/div>\n<p><span style=\"font-weight: 400;\">But there is one thing an Arduino cannot do &#8211; it can\u2019t tell the time.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">There are several time-related functions you can use when programming an Arduino:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">The <\/span><a href=\"https:\/\/www.arduino.cc\/reference\/en\/language\/functions\/time\/delay\/\" target=\"_blank\" rel=\"noopener noreferrer\"><i><span style=\"font-weight: 400;\">delay<\/span><\/i><\/a><span style=\"font-weight: 400;\"> function, which can delay program execution for a specified number of milliseconds.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">The <\/span><a href=\"https:\/\/www.arduino.cc\/reference\/en\/language\/functions\/time\/delaymicroseconds\/\" target=\"_blank\" rel=\"noopener noreferrer\"><i><span style=\"font-weight: 400;\">delayMicroseconds<\/span><\/i><\/a><span style=\"font-weight: 400;\"> function which is like the <\/span><i><span style=\"font-weight: 400;\">delay<\/span><\/i><span style=\"font-weight: 400;\"> function except you specify the time in microseconds.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">The <\/span><a href=\"https:\/\/www.arduino.cc\/reference\/en\/language\/functions\/time\/millis\/\" target=\"_blank\" rel=\"noopener noreferrer\"><i><span style=\"font-weight: 400;\">millis<\/span><\/i><\/a><span style=\"font-weight: 400;\"> function, which counts the elapsed milliseconds since the Arduino was powered up or reset.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">The <\/span><a href=\"https:\/\/www.arduino.cc\/reference\/en\/language\/functions\/time\/micros\/\" target=\"_blank\" rel=\"noopener noreferrer\"><i><span style=\"font-weight: 400;\">micros<\/span><\/i><\/a><span style=\"font-weight: 400;\"> function, like the <\/span><i><span style=\"font-weight: 400;\">millis<\/span><\/i><span style=\"font-weight: 400;\"> function, except it measures the time the Arduino has been running in microseconds.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">You can use the above functions to insert time delays or measure elapsed time. But you can\u2019t get the time of day or date from them.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">To do that you\u2019ll need to add an external component &#8211; a \u201creal time clock\u201d.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Real Time Clocks<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">A \u201creal time clock\u201d is essentially a digital clock whose output can be read by a computer or microcontroller. \u00a0It has its own oscillator that it uses to count time and it has registers that allow you to set the current time and date.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5584\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Real-Time_Clock-with-Arduino.jpeg?resize=750%2C422&#038;ssl=1\" alt=\"Real Time Clock with Arduino\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Real-Time_Clock-with-Arduino.jpeg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Real-Time_Clock-with-Arduino.jpeg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">The device you are using to read this article likely has a real time clock and if you are attached to the Internet you probably are synchronizing this to a network time server (if your device is a phone it may be time synchronized to your telephone companies carrier signal instead).<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Most real time clock modules have provision for a battery backup, so that they can keep time when the rest of the system is powered down.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Unix Time<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Most computers keep time in what might seem to be a strange system, they use \u201c<\/span><a href=\"https:\/\/en.wikipedia.org\/wiki\/Unix_time\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">Unix time<\/span><\/a><span style=\"font-weight: 400;\">\u201d.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Unix time is the number of seconds that have elapsed since midnight January 1, 1970 (which was a Thursday if you\u2019re interested). \u00a0If you are on Linux (or at the terminal on a Mac, which uses Unix as its underlying operating system) you can type \u201c<\/span><i><span style=\"font-weight: 400;\">date +%s<\/span><\/i><span style=\"font-weight: 400;\">\u201d to get the current Unix time.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Unix time is also called \u201cPOSIX Time\u201d or \u201cUNIX Epoch time\u201d. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">Unix time is useful when you are writing a program that needs to calculate the time difference between two dates and times, as it involves simple addition and subtraction, without having to worry about days, months and years.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">But Unix time also has a few drawbacks:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">It does not take into account leap seconds, and there have been several of these since January 1, 1970.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">It uses a 32-bit numbering system and will run out of digits on January 19, 2038. This is sometimes referred to as the \u201cYear 2038 problem\u201d.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">The issue with leap seconds is generally taken care of by synchronizing your real time clock with a local or network time source, which itself will have compensated for leap seconds.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The problem with 2038 is likely to be resolved within the next 19 years, I suspect just shifting to a 64-bit standard would resolve this for several millennia!<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">DS1307 Real Time Clock<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">There are a few very popular real time clock integrated circuits that are used in real time clock modules.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">One chip is the <\/span><a href=\"https:\/\/datasheets.maximintegrated.com\/en\/ds\/DS3231.pdf\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">DS3231<\/span><\/a><span style=\"font-weight: 400;\">, a highly accurate real time clock that uses an I2C interface. \u00a0This chip has its own internal crystal oscillator, so no external crystal is required.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Another very popular chip is the <\/span><a href=\"https:\/\/datasheets.maximintegrated.com\/en\/ds\/DS1307.pdf\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">DS1307<\/span><\/a><span style=\"font-weight: 400;\">. Like the DS3231 it also communicates using the I2C bus, however, this chip requires an external timing crystal.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The experiment I&#8217;ll be performing today use a module that has a DS1307 chip. \u00a0They can be easily modified to use the DS3231.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Tiny RTC Board<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">I will be using a module called the \u201cTiny RTC\u201d, this is a very common and inexpensive module.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5586\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Tiny-RTC-Front.jpg?resize=750%2C422&#038;ssl=1\" alt=\"Tiny RTC Front View\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Tiny-RTC-Front.jpg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Tiny-RTC-Front.jpg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">The board contains the DS1307 chip and all the support electronics, including the timing crystal. \u00a0It also has a battery holder for a coin cell, this sits underneath the board.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5585\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Tiny-RTC-Back.jpg?resize=750%2C422&#038;ssl=1\" alt=\"Tiny RTC Rear View\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Tiny-RTC-Back.jpg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Tiny-RTC-Back.jpg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">If you order your Tiny RTC online from an overseas source it likely won\u2019t have the battery installed, this is due to international shipping regulations regarding lithium batteries. The module uses a widely available coin cell battery.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The Tiny RTC module has the following features:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Counts time in hours, minutes and seconds<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Counts date, day of week, month and year.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Has Leap Year compensation<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Has a programmable square wave output.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Has battery backup with automatic power failure detection and switchover.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Consumes less than 500nA in battery backup mode.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">The Tiny RTC module interfaces using the I2C bus.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5587\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Tiny-RTC-Hookup.jpeg?resize=750%2C422&#038;ssl=1\" alt=\"Tiny RTC Pinouts\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Tiny-RTC-Hookup.jpeg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Tiny-RTC-Hookup.jpeg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">The module has two sets of connectors, the I2C connections are repeated on both of them and you can use either of them to make your connections.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The device has the following connections:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><b>DS<\/b><span style=\"font-weight: 400;\"> &#8211; Device Select, this allows you to enable or disable the device.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>SCL<\/b><span style=\"font-weight: 400;\"> &#8211; The I2C clock or SCL connection.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>SDA<\/b><span style=\"font-weight: 400;\"> &#8211; The I2C Serial Data or SDA connection.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>VCC<\/b><span style=\"font-weight: 400;\"> &#8211; The +5-volt power supply.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>GND<\/b><span style=\"font-weight: 400;\"> &#8211; The Ground connection.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>SQ<\/b><span style=\"font-weight: 400;\"> &#8211; The programmable Square Wave output.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>BAT<\/b><span style=\"font-weight: 400;\"> &#8211; Battery connection.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Now that you have seen the module let\u2019s hook it up to an Arduino.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Tiny RTC Basic Arduino Hookup<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">As the Tiny RTC uses the I2C bus it is very easy to hook it up to an Arduino. \u00a0The I2C bus provides power, clock and data signals, so only four connections are required.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Before you hook up your real time clock module it would be a good idea to install the coin cell battery, if you haven\u2019t already. That way you will ensure that the device will keep time even after you power down the Arduino.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Arduino Hookup<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Here is the hookup diagram for the Tiny RTC module.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5581\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-RTC-Hookup.jpeg?resize=750%2C422&#038;ssl=1\" alt=\"Tiny RTC Arduino Hookup\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-RTC-Hookup.jpeg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-RTC-Hookup.jpeg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">The two I2C connections are made to two of the Arduino analog inputs. <\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Analog pin A4 is the SDA connection.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Analog pin A5 is the SCL connection.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Some Arduino clones also have separate <\/span><i><span style=\"font-weight: 400;\">SDA<\/span><\/i><span style=\"font-weight: 400;\"> and <\/span><i><span style=\"font-weight: 400;\">SCL<\/span><\/i><span style=\"font-weight: 400;\"> pins, usually located on the same side as the digital I\/O pins above the <\/span><i><span style=\"font-weight: 400;\">AREF<\/span><\/i><span style=\"font-weight: 400;\"> pin. \u00a0You can use these connections instead of the analog pins if you wish, they are actually just duplicates.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Arduino Libraries<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">There are several libraries available that will work with the Tiny RTC. I\u2019m going to use two libraries that were contributed by Paul Stoffregen, a well-known figure in the Arduino community.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><a href=\"https:\/\/github.com\/PaulStoffregen\/DS1307RTC\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">DS1307RTC Library<\/span><\/a><span style=\"font-weight: 400;\"> &#8211; This library will function with any module that uses the DS1307 RTC chip, including the Tiny RTC.<\/span><\/li>\n<li style=\"font-weight: 400;\"><a href=\"https:\/\/github.com\/PaulStoffregen\/Time\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">Time Library<\/span><\/a><span style=\"font-weight: 400;\"> &#8211; This library compliments the DS1307RTC library and adds a number of time-specific functions.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">The Arduino Library Manager can be also used to install two updated versions of these libraries, these were updated by Michael Margolis. \u00a0You can find them as follows:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Open the Arduino IDE.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Click on the <\/span><i><span style=\"font-weight: 400;\">Sketch<\/span><\/i><span style=\"font-weight: 400;\"> menu item at the top of the IDE window.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Click on <\/span><i><span style=\"font-weight: 400;\">Include Library<\/span><\/i><span style=\"font-weight: 400;\">. A sub-menu will open.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Select <\/span><i><span style=\"font-weight: 400;\">Manage Libraries<\/span><\/i><span style=\"font-weight: 400;\"> from the sub-menu.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">The Arduino Library Manager will open.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">In the search box in the Library Manager type \u201c<\/span><i><span style=\"font-weight: 400;\">DS1307RTC<\/span><\/i><span style=\"font-weight: 400;\">\u201d<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">You should get two libraries in your results, the <\/span><i><span style=\"font-weight: 400;\">DS1307RTC<\/span><\/i><span style=\"font-weight: 400;\"> library, and the <\/span><i><span style=\"font-weight: 400;\">Time <\/span><\/i><span style=\"font-weight: 400;\">library.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">Click each selection to install the libraries.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">You can now close the Library Manager window.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Once you have the libraries installed open your Arduino IDE and select the <\/span><i><span style=\"font-weight: 400;\">File<\/span><\/i><span style=\"font-weight: 400;\"> menu item and select <\/span><i><span style=\"font-weight: 400;\">Examples<\/span><\/i><span style=\"font-weight: 400;\">. A sub-menu will appear, scroll down until you get to the<\/span><i><span style=\"font-weight: 400;\"> Examples from Custom Libraries<\/span><\/i><span style=\"font-weight: 400;\"> section. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">Look for <\/span><i><span style=\"font-weight: 400;\">DS1307RTC<\/span><\/i><span style=\"font-weight: 400;\"> and highlight it. You will see a sub-menu with two sketches, <\/span><i><span style=\"font-weight: 400;\">SetTime<\/span><\/i><span style=\"font-weight: 400;\"> and <\/span><i><span style=\"font-weight: 400;\">ReadTest<\/span><\/i><span style=\"font-weight: 400;\">.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We will run both of these, starting with <\/span><i><span style=\"font-weight: 400;\">SetTime<\/span><\/i><span style=\"font-weight: 400;\">.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">SetTime Sketch<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">As you might have guessed from its name the <\/span><i><span style=\"font-weight: 400;\">SetTime<\/span><\/i><span style=\"font-weight: 400;\"> sketch sets the time on the Tiny RTC module. You\u2019ll need to run this, or something similar, before you can use the clock.<\/span><\/p>\n<pre class=\"lang:default decode:true \" title=\"SetTime\">#include &lt;Wire.h&gt;\r\n#include &lt;Time.h&gt;\r\n#include &lt;DS1307RTC.h&gt;\r\n\r\nconst char *monthName[12] = {\r\n  \"Jan\", \"Feb\", \"Mar\", \"Apr\", \"May\", \"Jun\",\r\n  \"Jul\", \"Aug\", \"Sep\", \"Oct\", \"Nov\", \"Dec\"\r\n};\r\n\r\ntmElements_t tm;\r\n\r\nvoid setup() {\r\n  bool parse=false;\r\n  bool config=false;\r\n\r\n  \/\/ get the date and time the compiler was run\r\n  if (getDate(__DATE__) &amp;&amp; getTime(__TIME__)) {\r\n    parse = true;\r\n    \/\/ and configure the RTC with this info\r\n    if (RTC.write(tm)) {\r\n      config = true;\r\n    }\r\n  }\r\n\r\n  Serial.begin(9600);\r\n  while (!Serial) ; \/\/ wait for Arduino Serial Monitor\r\n  delay(200);\r\n  if (parse &amp;&amp; config) {\r\n    Serial.print(\"DS1307 configured Time=\");\r\n    Serial.print(__TIME__);\r\n    Serial.print(\", Date=\");\r\n    Serial.println(__DATE__);\r\n  } else if (parse) {\r\n    Serial.println(\"DS1307 Communication Error :-{\");\r\n    Serial.println(\"Please check your circuitry\");\r\n  } else {\r\n    Serial.print(\"Could not parse info from the compiler, Time=\\\"\");\r\n    Serial.print(__TIME__);\r\n    Serial.print(\"\\\", Date=\\\"\");\r\n    Serial.print(__DATE__);\r\n    Serial.println(\"\\\"\");\r\n  }\r\n}\r\n\r\nvoid loop() {\r\n}\r\n\r\nbool getTime(const char *str)\r\n{\r\n  int Hour, Min, Sec;\r\n\r\n  if (sscanf(str, \"%d:%d:%d\", &amp;Hour, &amp;Min, &amp;Sec) != 3) return false;\r\n  tm.Hour = Hour;\r\n  tm.Minute = Min;\r\n  tm.Second = Sec;\r\n  return true;\r\n}\r\n\r\nbool getDate(const char *str)\r\n{\r\n  char Month[12];\r\n  int Day, Year;\r\n  uint8_t monthIndex;\r\n\r\n  if (sscanf(str, \"%s %d %d\", Month, &amp;Day, &amp;Year) != 3) return false;\r\n  for (monthIndex = 0; monthIndex &lt; 12; monthIndex++) {\r\n    if (strcmp(Month, monthName[monthIndex]) == 0) break;\r\n  }\r\n  if (monthIndex &gt;= 12) return false;\r\n  tm.Day = Day;\r\n  tm.Month = monthIndex + 1;\r\n  tm.Year = CalendarYrToTm(Year);\r\n  return true;\r\n}\r\n<\/pre>\n<p><span style=\"font-weight: 400;\">SetTime uses two functions, getTime and getDate, to retrieve the time and date respectively from your computer clock. As most Internet-connected computers synchronize to a network time protocol (NTP) server this will probably be very accurate.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">One statement in the code that may be new to you is the 10th line, <\/span><i><span style=\"font-weight: 400;\">tmElements_t tm;<\/span><\/i><span style=\"font-weight: 400;\"> . \u00a0This is a \u201cdata structure\u201d that represents the time.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Without using a data structure the time will be reported in Unix time, which I described earlier. \u00a0The <\/span><i><span style=\"font-weight: 400;\">tmElements_t <\/span><\/i><span style=\"font-weight: 400;\">\u00a0data structure breaks this down into elements like seconds, minutes, hours, days, months and years.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Otherwise, the sketch is fairly straightforward. It gets the current system time from the computer running the IDE and writes it to the DS1307 chip on the Tiny RTC module. It does all of this in the Setup section so there is no code in the loop.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Load this sketch and run it to set the time in your real time clock. Then move on to the next sketch.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">ReadTest Sketch<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">The ReadTest sketch will read the time from the Tiny RTC module or any module based upon the DS1307 real time clock chip.<\/span><\/p>\n<pre class=\"lang:default decode:true \" title=\"ReatTest\">#include &lt;Wire.h&gt;\r\n#include &lt;Time.h&gt;\r\n#include &lt;DS1307RTC.h&gt;\r\n\r\nvoid setup() {\r\n  Serial.begin(9600);\r\n  while (!Serial) ; \/\/ wait for serial\r\n  delay(200);\r\n  Serial.println(\"DS1307RTC Read Test\");\r\n  Serial.println(\"-------------------\");\r\n}\r\n\r\nvoid loop() {\r\n  tmElements_t tm;\r\n\r\n  if (RTC.read(tm)) {\r\n    Serial.print(\"Ok, Time = \");\r\n    print2digits(tm.Hour);\r\n    Serial.write(':');\r\n    print2digits(tm.Minute);\r\n    Serial.write(':');\r\n    print2digits(tm.Second);\r\n    Serial.print(\", Date (D\/M\/Y) = \");\r\n    Serial.print(tm.Day);\r\n    Serial.write('\/');\r\n    Serial.print(tm.Month);\r\n    Serial.write('\/');\r\n    Serial.print(tmYearToCalendar(tm.Year));\r\n    Serial.println();\r\n  } else {\r\n    if (RTC.chipPresent()) {\r\n      Serial.println(\"The DS1307 is stopped.  Please run the SetTime\");\r\n      Serial.println(\"example to initialize the time and begin running.\");\r\n      Serial.println();\r\n    } else {\r\n      Serial.println(\"DS1307 read error!  Please check the circuitry.\");\r\n      Serial.println();\r\n    }\r\n    delay(9000);\r\n  }\r\n  delay(1000);\r\n}\r\n\r\nvoid print2digits(int number) {\r\n  if (number &gt;= 0 &amp;&amp; number &lt; 10) {\r\n    Serial.write('0');\r\n  }\r\n  Serial.print(number);\r\n}\r\n<\/pre>\n<p><span style=\"font-weight: 400;\">This is actually a pretty simple sketch, and it does a good job of illustrating how you can use these libraries to write a sketch of your own.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We start by including the Wire library, which is the built-in library that facilitates communications using I2C. \u00a0We then include the two libraries we installed earlier.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In the Setup section we just set up the serial monitor and write a few lines to it.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The Loop starts with our data structure to derive the time values from.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Al that is left is to read those time values and print them to the serial monitor. A function called <\/span><i><span style=\"font-weight: 400;\">print2digits<\/span><\/i><span style=\"font-weight: 400;\"> is used for the hours, minutes and seconds to format the display nicely, with leading zeros for numbers below 10.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">I&#8217;ll be reusing a lot of this code later when I create a sketch of my own.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Tiny RTC Square Wave Interrupt<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">The two sketches we have just looked at illustrate how to set and read the time from the Tiny RTC module, and they accomplish this very well. But the module has an additional function, the ability to output a square wave.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">You can use this square wave as a timing source for another circuit. It could be used to drive a stepper motor to create an analog clock. And, as I will show you here, it can be used to generate an interrupt for your Arduino.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Programming the Tiny RTC Square Wave Frequency<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">The DS1307 chip used in the Tiny RTC module is capable of generating square waves at the following preset frequencies:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">1 Hz<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">4 KHz<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">8 KHz<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">32 KHz<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">These frequencies are selected by writing to an internal control register in the DS1307. \u00a0By default, the device is programmed at the factory for a 32 KHz frequency.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Square Wave Arduino Hookup<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">To use the square wave output as an interrupt for your Arduino you will need to connect the SQ output on the Tiny RTC module to one of the interrupt pins on the Arduino.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The following diagram shows the hookup using an Arduino Uno.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5582\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-RTC-with-SQ-Wave-Hookup.jpeg?resize=750%2C422&#038;ssl=1\" alt=\"Arduino Real Time Clock with Square Wave Interrupt\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-RTC-with-SQ-Wave-Hookup.jpeg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-RTC-with-SQ-Wave-Hookup.jpeg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">The SQ output is connected to pin 2, which corresponds to interrupt 0 in the Arduino Uno.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">An LED is also connected to the Arduino to indicate when an interrupt is being serviced. This is actually optional as it is connected to pin 13 and the Uno also has a built-in LED connected to that pin. If you wish you can leave it out and just monitor the LED on your Uno board.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Square Wave Interrupt Demo Sketch<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">I found a great sketch that shows how to use the square wave output, it was originally published by Robert Ulbricht on the <\/span><a href=\"https:\/\/www.arduinoslovakia.eu\/blog\/2017\/9\/ds1307-a-signal-obdlznikoveho-priebehu?lang=en\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">Arduino Slovakia website<\/span><\/a><span style=\"font-weight: 400;\">. Fortunately, there is an English translation available.<\/span><\/p>\n<pre class=\"lang:default decode:true \" title=\"Set SQW Interrupt\">\/**\r\n   Arduino DS1307 Set SQW Interrupt\r\n   v. 1.0\r\n   Copyright (C) 2017 Robert Ulbricht\r\n   http:\/\/www.arduinoslovakia.eu\r\n\r\n   Set Square Wave Output 1Hz.\r\n   Blink with internal LED using interrupt.\r\n\r\n   IDE: 1.8.3 or higher\r\n   Board: Arduino Uno, Arduino Pro Mini, Arduino Mega 2560\r\n\r\n   Libraries: none\r\n\r\n   This program is free software: you can redistribute it and\/or modify\r\n   it under the terms of the GNU General Public License as published by\r\n   the Free Software Foundation, either version 3 of the License, or\r\n   (at your option) any later version.\r\n\r\n   This program is distributed in the hope that it will be useful,\r\n   but WITHOUT ANY WARRANTY; without even the implied warranty of\r\n   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the\r\n   GNU General Public License for more details.\r\n\r\n   You should have received a copy of the GNU General Public License\r\n   along with this program.  If not, see &lt;http:\/\/www.gnu.org\/licenses\/&gt;.\r\n*\/\r\n\r\n#include &lt;Wire.h&gt;\r\n\r\n#define DS1307_CTRL_ID 0x68\r\n#define ledPin LED_BUILTIN\r\n\r\nvoid setSQW(uint8_t value) {\r\n  Wire.beginTransmission(DS1307_CTRL_ID);\r\n  Wire.write(7);\r\n  Wire.write(value);\r\n  Wire.endTransmission();\r\n}\r\n\r\nvoid handleInt() {\r\n  digitalWrite(ledPin, digitalRead(ledPin) ^ 1);\r\n}\r\n\r\nvoid setup() {\r\n  Serial.begin(9600);\r\n  while (!Serial) ; \/\/ wait for serial\r\n  delay(200);\r\n  Serial.println(\"DS1307RTC Set SQW 1 Hz\");\r\n  Serial.println(\"Attach interrupt on D2\");\r\n  Serial.println(\"----------------------\");\r\n\r\n  pinMode(ledPin,OUTPUT);\r\n\r\n  \/\/ D2 on Arduino Uno\r\n  \/\/ D2 on Arduino Mega 2560\r\n  attachInterrupt(0,handleInt,FALLING);\r\n\r\n  \/\/ 1Hz\r\n  setSQW(0x10);\r\n}\r\n\r\nvoid loop() {\r\n}\r\n<\/pre>\n<p><span style=\"font-weight: 400;\">The sketch only requires the <\/span><i><span style=\"font-weight: 400;\">Wire<\/span><\/i><span style=\"font-weight: 400;\"> library, it uses this to write directly to the registers on the DS1307 chip.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The constant <\/span><i><span style=\"font-weight: 400;\">DS1307_CTRL_ID<\/span><\/i><span style=\"font-weight: 400;\"> defines the I2C address of the real time clock chip.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The function <\/span><i><span style=\"font-weight: 400;\">setSQW<\/span><\/i><span style=\"font-weight: 400;\"> is really where the \u201caction\u201d is. This function writes to the control register in the DS1307 and sets the square wave frequency to 1Hz.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The <\/span><i><span style=\"font-weight: 400;\">handleInt<\/span><\/i><span style=\"font-weight: 400;\"> function is the interrupt handler. Every time a pulse is received on the D2 pin it will be called. \u00a0This is set up in the Setup function using the <\/span><a href=\"https:\/\/www.arduino.cc\/reference\/en\/language\/functions\/external-interrupts\/attachinterrupt\/\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">Arduino attachInterrupt function<\/span><\/a><span style=\"font-weight: 400;\">.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The result is that the LED will flash every second. \u00a0In operation, it looks a lot like the Blink sketch!<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Tiny RTC Temperature and Humidity Sketch<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">The previous sketch illustrated how to use the SQ square wave output from the Tiny RTC module as an interrupt. And while it does a great job of displaying interrupt operation it really doesn\u2019t have many practical uses.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">After all, there are many simpler methods of blinking an LED. In fact, if you really wanted to use the Tiny RTC to blink an LED you could just attach it directly to the SQ output, eliminating the Arduino entirely (although you\u2019d need the Arduino to set the SQ output to 1Hz first).<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Let\u2019s look at a more practical example of using interrupts from the real time clock module.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Using Interrupts to Solve a Problem<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Take another look at the <\/span><i><span style=\"font-weight: 400;\">ReadTest<\/span><\/i><span style=\"font-weight: 400;\"> sketch from the DS1307RTC examples. You\u2019ll notice that it reads the time and then adds two delays that total exactly one second. It then does it all over again. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">If you\u2019re just building a clock this will work well, as every second you\u2019ll read the time and it will have advanced one second. \u00a0But what if you want to do something else in the Loop after you read and display the time?<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Whatever your \u201csomething else\u201d is it probably won\u2019t take exactly one second. And this will cause an erratic clock display.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">If the \u201dsomething else\u201d takes less than a second then you\u2019ll be displaying the same time more than once. On a display like an LCD or OLED this is not such a bad thing as you might never notice it, but on the serial monitor it will stand out.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">If the \u201csomething else\u201d takes more than one second you\u2019ll miss reading the clock and it wil skip one or more seconds. You can alleviate this problem somewhat by simply not displaying seconds but still, your minutes may not change at precisely the right time.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">To solve this timing problem we can use interrupts.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">AM2320 Temperature &amp; Humidity Sensor<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">To illustrate how to take advantage of interrupts to solve the timing problem I\u2019m going to build a temperature and humidity meter that can also tell time. \u00a0I\u2019m going to stick to the serial monitor for my display, but you could easily modify the code to use an OLED or LCD display.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The AM2320 is an I2C temperature and humidity sensor. Physically it looks identical to a DHT11 or DHT22, the difference is that it uses the I2C bus to send data to its host.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">If you wish you could modify the sketch to use the DHT22 or DHT11, I used the AM2320 because I was already using I2C for the real time clock and because I had one handy!<\/span><\/p>\n<p><span style=\"font-weight: 400;\">No matter which sensor you choose for your design you\u2019ll encounter the same dilemma &#8211; these temperature and humidity sensors require at least two seconds between readings to stabilize. \u00a0And so if you read it in the Loop you\u2019ll get an erratic display.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">This looks like a job for an interrupt!<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Temperature and Humidity Clock Hookup<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Let\u2019s begin by adding an AM2320 to our existing circuit. As you can see it\u2019s pretty easy.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5583\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-RTC-with-Temp-Humid-Hookup.jpeg?resize=750%2C422&#038;ssl=1\" alt=\"Arduino Real Time Clock and Temperature Humidity Sensor\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-RTC-with-Temp-Humid-Hookup.jpeg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-RTC-with-Temp-Humid-Hookup.jpeg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">Pay attention to the connections on the AM2320, looking at the unit with the \u201cgrid holes\u201d facing you they are as follows, from left to right:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">VCC &#8211; Goes to the +5 Volt output from the Arduino.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">SDA &#8211; To Arduino pin A4 (or SDA pin if you have one)<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">GND &#8211; To Arduino Ground.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">SCL &#8211; To Arduino pin A5 (or SCL pin if you have one)<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Now that you have it hooked up let\u2019s take a look at the sketch I came up with to make it all work.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Temperature and Humidity Clock Sketch<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">You\u2019ll probably notice many elements from the previous sketches in this sketch.<\/span><\/p>\n<pre class=\"lang:default decode:true \" title=\"Time Temp Humid\">\/*\r\n  Time, Temperature and Humidity\r\n  time_temp_humid.ino\r\n  Displays results on Serial Monitor\r\n  Uses AM2320 I2C Temperature and Humidity sensor\r\n  Uses DS1307 Real Time Clock\r\n  Uses TimeLib Library\r\n  Uses DS1307RTC Library\r\n  Uses Adafruit AM2320 Library\r\n  \r\n  DroneBot Workshop 2019\r\n  <blockquote class=\"wp-embedded-content\" data-secret=\"NgYye9KO7J\"><a href=\"https:\/\/dronebotworkshop.com\/\">Welcome to the Workshop!<\/a><\/blockquote><iframe class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; clip: rect(1px, 1px, 1px, 1px);\" title=\"&#8220;Welcome to the Workshop!&#8221; &#8212; DroneBot Workshop\" src=\"https:\/\/dronebotworkshop.com\/embed\/#?secret=6aHDrfBC5F#?secret=NgYye9KO7J\" data-secret=\"NgYye9KO7J\" width=\"600\" height=\"338\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe>\r\n*\/\r\n\r\n\/\/ Include required libraries\r\n#include &lt;Wire.h&gt;\r\n#include &lt;TimeLib.h&gt;\r\n#include &lt;DS1307RTC.h&gt;\r\n#include &lt;Adafruit_AM2320.h&gt;\r\n\r\n\/\/ Define constant for RTC I2C Address\r\n#define DS1307_CTRL_ID 0x68\r\n\r\n\/\/ Define object am2320\r\nAdafruit_AM2320 am2320 = Adafruit_AM2320();\r\n\r\n\/\/ Variables to count square wave pulses\r\nint ticks = 0;\r\nint old_tick_value = 0;\r\n\r\n\/\/ Variables for Humidity and Temperature\r\nfloat h;\r\nfloat t;\r\n\r\nvoid setup() {\r\n  Serial.begin(9600);\r\n  \r\n  \/\/ Attach Interrupt to pin D2\r\n  attachInterrupt(0,handleInt,FALLING);\r\n\r\n  \/\/ Set Square Wave at 1Hz\r\n  setSQW(0x10);\r\n  \r\n  \/\/ Initialize Temp &amp; Humid Sensor\r\n  am2320.begin();\r\n\r\n  delay(2000);\r\n\r\n  \/\/ Read Humidity\r\n  h = am2320.readHumidity();\r\n  \/\/ Read temperature as Celsius\r\n  t = am2320.readTemperature();\r\n}\r\n\r\nvoid loop() {\r\n\r\n\/\/ Read Temp Humid sensor every 10 seconds    \r\nif (ticks ==10){\r\n   \/\/ Read Humidity\r\n    h = am2320.readHumidity();\r\n    \/\/ Read temperature as Celsius\r\n    t = am2320.readTemperature();\r\n    ticks = 0;\r\n\r\n  }\r\n\r\n\/\/ Update serial monitor display if a second has elapsed  \r\nif (ticks != old_tick_value) {\r\n        old_tick_value = ticks;\r\n        printCurrentTime(h,t);\r\n    }\r\n\r\n}\r\n\r\n\/\/ Interrupt Handler\r\nvoid handleInt() {\r\n  ticks++;\r\n  \r\n}\r\n\r\n\/\/ Setup RTC Module for 1 Hz square wave\r\nvoid setSQW(uint8_t value) {\r\n  Wire.beginTransmission(DS1307_CTRL_ID);\r\n  Wire.write(7);\r\n  Wire.write(value);\r\n  Wire.endTransmission();\r\n}\r\n\r\n\/\/ Format numbers as 2-digit numbers\r\nvoid print2digits(int number) {\r\n  if (number &gt;= 0 &amp;&amp; number &lt; 10) {\r\n    Serial.print('0');\r\n  }\r\n  Serial.print(number);\r\n}\r\n\r\n\/\/ Print to the serial monitor\r\nvoid printCurrentTime(float hum, float tem){\r\ntmElements_t tm;\r\n\r\n  if (RTC.read(tm)) {\r\n    print2digits(tm.Hour);\r\n    Serial.print(':');\r\n    print2digits(tm.Minute);\r\n    Serial.print(':');\r\n    print2digits(tm.Second);\r\n    Serial.print(\" - \");\r\n    Serial.print(tmYearToCalendar(tm.Year));\r\n    Serial.print('-');\r\n    print2digits(tm.Month);\r\n    Serial.print('-');\r\n    print2digits(tm.Day);\r\n    Serial.print(\" Hum: \");\r\n    Serial.print(hum);\r\n    Serial.print(\"% - Temp: \");\r\n    Serial.print(tem);\r\n    Serial.print(\" C\");\r\n    \r\n    Serial.println();\r\n  }\r\n}\r\n<\/pre>\n<p><span style=\"font-weight: 400;\">You\u2019ll need another couple of libraries to run this sketch to handle the temperature and humidity sensor. Both can be installed using the Library Manager.<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">The Adafruit AM2320 Library<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">The Adafruit Unified Sensor Library.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">The latter library is not called directly in the sketch, instead, it is used by the AM2320 Library. Without it installed your sketch will fail to compile. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">If you\u2019ve used other Adafruit sensor libraries you may already have the Unified Sensor library installed.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We begin the sketch by including the libraries. \u00a0We then define the constant we used before for the Tiny RTC I2C address.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We also create an object to represent our sensor.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Next, we create a couple of variables that count \u201cticks\u201d. I\u2019m defining a \u201ctick\u201d as a one second period. The <\/span><i><span style=\"font-weight: 400;\">old_tick_value<\/span><\/i><span style=\"font-weight: 400;\"> variable will be used to check if the tick value has changed since we last used it.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">A couple of floats are defined to hold the temperature and humidity values.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In the Setup routine we attach the interrupt to the interrupt handler, as we did earlier. I kept the same name for the interrupt handler but have changed its function.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We also setup the square wave as 1 Hz. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">Next we initialize the temperature and humidity sensor, delay for two seconds and then read the temperature and humidity values. This is so we already have a first reading before we enter the loop.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Let&#8217;s look down to some of the functions before we examine the Loop.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The <\/span><i><span style=\"font-weight: 400;\">printCurrentTime<\/span><\/i><span style=\"font-weight: 400;\"> function prints the time, date, temperature and humidity to the serial monitor. It takes the temperature and humidity as an input and reads the real time clock, it then writes everything to the serial monitor.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The interrupt handler <\/span><i><span style=\"font-weight: 400;\">handleInt<\/span><\/i><span style=\"font-weight: 400;\"> increments the tick count every time it is run. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">You\u2019ve seen the other two functions already, so let\u2019s go back up to the loop.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In the Loop we first check the number of ticks by reading the tick count. If it is 10 then we read the humidity and temperature, then reset the tick counter to zero.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">By doing this we only read the temperature and humidity sensor every 10 seconds, which gives it plenty of time to stabilize. You can reduce this number if you wish, but don\u2019t go below two seconds.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We then check to see if the tick count is the same as it was before. If it is then we don\u2019t do anything. If it isn\u2019t then it means a second has elapsed, so we call <\/span><i><span style=\"font-weight: 400;\">printCurrentTime <\/span><\/i><span style=\"font-weight: 400;\">\u00a0to read the time and write everything to the serial monitor.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Load the sketch and give it a test. Note that since the temperature and humidity are only updated every 10 seconds it won\u2019t immediately respond to a change in these values. In normal situations this shouldn&#8217;t really be an issue.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Conclusion<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Adding a real time clock to an Arduino makes it possible to build devices that are aware of the current time and date. This can allow you to create fancy timers and delay circuits, or just build a really cool and unique digital clock.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Hopefully you\u2019ll see some uses for a real time clock in your own projects. There no time like the present to get started!<\/span><\/p>\n<p>&nbsp;<\/p>\n<div class=\"dbwspartsbox\">\n<h3>Parts List<\/h3>\n<p><em>Here are some components that you might need to complete the experiments in this article. Please note that some of these links may be affiliate links, and the DroneBot Workshop may receive a commission on your purchases. This does not increase the cost to you and is a method of supporting this ad-free website.<\/em><\/p>\n<p>COMING SOON!<\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"dbwsresourcebox\">\n<h3>Resources<\/h3>\n<p><a href=\"https:\/\/s3.amazonaws.com\/download.dronebotworkshop.com\/Real+Time+Clock+-+DroneBot+Workshop.zip\">Code In this Article<\/a> &#8211; The sketches in this article in a ZIP file.<\/p>\n<\/div>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Introduction The Arduino is an amazing device. It\u2019s useful for prototyping and can also be used to construct a complete project. It has an analog to digital converters (ADC), digital I\/O pins, it handles interrupts and it can communicate via<\/p>\n","protected":false},"author":1,"featured_media":5584,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[9,60,90],"tags":[44],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Real-Time_Clock-with-Arduino.jpeg?fit=768%2C432&ssl=1","jetpack_shortlink":"https:\/\/wp.me\/p74ClK-1rZ","jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/posts\/5579"}],"collection":[{"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/comments?post=5579"}],"version-history":[{"count":2,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/posts\/5579\/revisions"}],"predecessor-version":[{"id":9943,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/posts\/5579\/revisions\/9943"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/media\/5584"}],"wp:attachment":[{"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/media?parent=5579"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/categories?post=5579"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/tags?post=5579"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}