We’re not sure if [Derek Lieber] is messing with us or proving a point. Why are you doing this [Derek]? We know there’s technically enough information to build the clock. You even included the code. Couldn’t you have at least thrown in a couple of words? Do we have to skip straight to mediaglyphics?

Anyway, if we follow the equation. The equation… If you take a gps module, a 7 segment display with an HT16K33 backpack, a digital potentiometer, a piezo, and a boarduino we suppose we could grudgingly admit that these would all fit together to make a clock. We still don’t like it though, but we’ll admit that the nice handmade case was a nice touch, and that the pictures do give us enough details to do it ourselves.

It was also pretty cool when you added the Zelda theme song as an alarm sound. Also pretty neat that, being GPS corrected, there’s no need to ever set the time. We may also like the simplicity of the only inputs being the potentiometer, which is used to set the alarm time. It’s just. Dangit [Derek]. Nice clock build, we like it.

[Brett] was looking for a way to improve on an old binary clock project from 1996. His original clock used green LEDs to denote between a one or a zero. If the LED was lit up, that indicated a one. The problem was that the LEDs were too dim to be able to read them accurately from afar. He’s been wanting to improve on his project using seven segment displays, but until recently it has been cost prohibitive.

[Brett] wanted his new project to use 24 seven segment displays. Three rows of eight displays. To build something like this from basic components would require the ability to switch many different LEDs for each of the seven segment displays. [Brett] instead decided to make things easier by using seven segment display modules available from Tindie. These modules each contain eight displays and are controllable via a single serial line.

The clock’s brain is an ATmega328 running Arduino. The controller keeps accurate time using a DCF77 receiver module and a DCF77 Arduino library. The clock comes with three display modes. [Brett] didn’t want and physical buttons on his beautiful new clock, so he opted to use remote control instead. The Arduino is connected to a 433MHz receiver, which came paired with a small remote. Now [Brett] can change display modes using a remote control.

A secondary monochrome LCD display is used to display debugging information. It displays the time and date in a more easily readable format, as well as time sync information, signal quality, and other useful information. The whole thing is housed in a sleek black case, giving it a professional look.

Introduction

The subject of our latest kit review is the “Epoch Clock” from Maniacal Labs, a new organisation started by three young lads with some interesting ideas. Regular readers will know we love a clock – so when the opportunity came to review this one, we couldn’t say no.

At this point you may be thinking “what is Epoch time anyway?”. Good question! It is the number of seconds elapsed since the first of January, 1970 (UTC) – and used by Unix-based computers as the start of their time universe. (For more on the theory of Epoch time, check out Wikipedia). For example – 1379226077 Epoch time is Sun, 15 Sep 2013 06:21:17 GMT. That’s a lot of seconds. If you’re curious, you can do more calculations with the EpochTime website.

Moving forward, this clock kit will show Epoch time in full 32-bit binary glory, using a DS1307 real-time clock IC (with backup battery) and is controlled with an ATmega328P-PU – so you can modify the code easily with the Arduino IDE or WinAVR (etc).

Assembly

The creators have spent a lot of time on not only the packaging and out-of-box-experience, but also the documentation and setup guide – so as long as you’re fine with simple through-hole soldering the kit will not present any challenges. The kit arrives in a sturdy box:

… with well packaged components. Everything is included for the finished product, as well as IC sockets, the RTC backup battery and a USB cable so you can power the clock from a USB hub:

The PCB is a good thickness, and has a clear silk-screen and solder mask:

Construction is simple, just follow the step-by-step instructions. Starting with the USB socket for power:

… then the resistors:

… the LEDs:

… all 32 of them. Note that the LEDs don’t sit flush with the PCB, so a little effort is required to keep them aligned:

 Then the rest of the components just fit as expected. I’ve also added the included header pins for an FTDI programming cable and ICSP to keep my options open:

Then simply fit the battery, insert the ICs and you’re done:

Using the clock

The microcontroller is pre-programmed, so you can use the clock straight away. You will however need to set the time first. To make this incredibly easy, there is a special web page that displays the current time and Epoch time, which steps you through the process of setting the time using the buttons.

Or with some code available on the kit github page and a programming cable, you can automatically sync it to the clock. Once setup, the battery will keep the current time in the RTC nicely. The clock is powered by 5V, which is easily supplied with the included USB cable, or you can always hack in your own feed.

So what does Epoch time in 32-bit binary look like? Here’s a short video of the clock in action:

Reading the time requires converting the binary number displayed with the LEDs back to a decimal number – which is of course the Epoch count of seconds since 1/1/1970. Math teachers will love this thing.

But wait, there’s more!

If you get tired of the blinking, there’s a test function which is enabled by holding down both buttons for a second, which turns the Epoch Clock into a nifty Larson Scanner:

To create your own sketches or examine the design files in more detail, it’s all on the clock github page. From a hardware perspective you have an ATmega328P-PU development board with a DS1307 battery-backed real-time clock – with 32 LEDs. So you could also create your own kind of clock or other multi-LED blinking project without too much effort. Review the EpochClockSchematic (.pdf) to examine this in more detail.

Conclusion

I really enjoyed this kit – it was easy to assemble, I learned something new and frankly the blinking LEDs can be quite soothing. The clock would make a great for a conversation-starter in the office, or would make an ideal gift for any Sheldon Cooper-types you might be associated with. Or have competitions to see who can convert the display to normal time. After shots.

Nevertheless it’s a fun and imaginative piece of kit, fully Open Hardware-compliant – and if you’ve made it this far – get some and have fun. Full-sized images are on flickr. Interested in Arduino? Check out my new book “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

[Note – The kit reviewed was a promotional consideration from Maniacal Labs]

The post Kit Review – Maniacal Labs Epoch Clock appeared first on tronixstuff.

Use the NXP PCF8563 real-time clock IC with Arduino in chapter fifty-four of our Arduino Tutorials. The first chapter is here, the complete series is detailed here.

Updated 20/08/2013

Introduction

Recently a few people have been asking about the PCF8563 real-time clock IC from NXP – so this is a tutorial on how to use it for time, date, alarm clock and square-wave generation purposes.

The PCF8563 is another inexpensive RTC that can be used with an Arduino or other platforms due to the wide operating voltage (1 to 5.5V DC), I2C interface, and very low power consumption (when powered by a backup battery it only draws 0.25 μA). If you aren’t up to speed on the I2C interface, please review the I2C tutorials before moving forward. And please download the data sheet (.pdf).

The PCF8563 is available in various chip packages, for the curious we’re using the TSSOP8 version mounted on a breakout board:

Don’t panic – you can also get it in a breadboard-friendly DIP (through-hole) package as well, and also on a pre-built module from the usual suspects.

Demonstration Circuit

If you have a pre-made module, you can skip to the next section. However if you’re making up the circuit yourself, you will need:

• One 32.768 kHz crystal
• Two 1N4148 diodes*
• One 3V coin cell (with holder)*
• Two 10kΩ resistors
• One 0.1 uF capacitor

And here’s the schematic:

* You can skip the diodes and battery if you don’t want a backup power supply when the main power is turned off or removed. Pin 3 is for the interrupt output (we’ll consider that later) and pin 7 is for the square-wave oscillator output.

Communicating with the PCF8563

Now to get down into the land of I2C once more. When looking through the data sheet NXP mentions two bus addresses, which have the same 7-bits finished with either a 1 for read or 0 for write. However you can just bitshift it over one bit as we don’t need the R/W bit – which gives you a bus address of 0x51.

Next you need to know which registers store the time and date – check the register map (table 4) on page 7 of the data sheet:

 There will be a few other registers of interest, but we’ll return to those later. For now, note that the time and date start from 0x02. And one more thing – data is stored in the BCD (binary-coded- decimal) format. But don’t panic, we have a couple of functions to convert numbers between BCD and decimal.

Writing the time and date is a simple matter of collating the seconds, minutes, hours, day of week, day of month, month and year into bytes, converting to BCD then sending them to the PCF8563 with seven Wire.write() functions. Reading the data is also easy, just set the pointer to 0x02 and request seven bytes of data – then run them through a BCD to decimal conversion. With a catch.

And that catch is the need to sort out unwanted bits. Revisit table 4 in the data sheet – if you see an x that’s an unused bit. If any of them are a 1 they will mess up the BCD-decimal conversion when reading the register, so they need to be eliminated just like a whack-a-mole. To do this, we perform an & (bitwise AND) operation on the returned byte and mask out the unwanted bits with a zero. How does that work?

Example – the byte for dayOfMonth is returned – we only need bits 5 to 0. So 6 and 7 are superfluous. If you use (dayOfMonth & B00111111) the & function will set bits 6 and 7 to zero, and leave the other bits as they were.

Now to put all that together in a demonstration sketch. It puts everything mentioned to work and simply sets the time to the PCF8563, and then returns it to the serial monitor. The data is kept in global variables declared at the start of the sketch, and the conversions between BCD and decimal are done “on the fly” in the functions used to send or retrieve data from the PCF8563. Read through the following sketch and see how it works for yourself:

// Example 54.1 - PCF8563 RTC write/read demonstration

#include "Wire.h"
#define PCF8563address 0x51

byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
String days[] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };

byte bcdToDec(byte value)
{
  return ((value / 16) * 10 + value % 16);
}

byte decToBcd(byte value){
  return (value / 10 * 16 + value % 10);
}

void setPCF8563()
// this sets the time and date to the PCF8563
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x02);
  Wire.write(decToBcd(second));  
  Wire.write(decToBcd(minute));
  Wire.write(decToBcd(hour));     
  Wire.write(decToBcd(dayOfMonth));
  Wire.write(decToBcd(dayOfWeek));  
  Wire.write(decToBcd(month));
  Wire.write(decToBcd(year));
  Wire.endTransmission();
}

void readPCF8563()
// this gets the time and date from the PCF8563
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x02);
  Wire.endTransmission();
  Wire.requestFrom(PCF8563address, 7);
  second     = bcdToDec(Wire.read() & B01111111); // remove VL error bit
  minute     = bcdToDec(Wire.read() & B01111111); // remove unwanted bits from MSB
  hour       = bcdToDec(Wire.read() & B00111111); 
  dayOfMonth = bcdToDec(Wire.read() & B00111111);
  dayOfWeek  = bcdToDec(Wire.read() & B00000111);  
  month      = bcdToDec(Wire.read() & B00011111);  // remove century bit, 1999 is over
  year       = bcdToDec(Wire.read());
}

void setup()
{
  Wire.begin();
  Serial.begin(9600);
  // change the following to set your initial time
  second = 0;
  minute = 28;
  hour = 9;
  dayOfWeek = 2;
  dayOfMonth = 13;
  month = 8;
  year = 13;
  // comment out the next line and upload again to set and keep the time from resetting every reset
  setPCF8563();
}

void loop()
{
  readPCF8563();
  Serial.print(days[dayOfWeek]); 
  Serial.print(" ");  
  Serial.print(dayOfMonth, DEC);
  Serial.print("/");
  Serial.print(month, DEC);
  Serial.print("/20");
  Serial.print(year, DEC);
  Serial.print(" - ");
  Serial.print(hour, DEC);
  Serial.print(":");
  if (minute < 10)
  {
    Serial.print("0");
  }
  Serial.print(minute, DEC);
  Serial.print(":");  
  if (second < 10)
  {
    Serial.print("0");
  }  
  Serial.println(second, DEC);  
  delay(1000);
}

And a quick video of this in operation:

If all you need to do is write and read the time with the PCF8563, you’re ready to go. However there’s a few more features of this unassuming little part which you might find useful, so at least keep reading…

Square-wave output

As with any clock or RTC IC, an oscillator is involved, and as mentioned earlier you can take this from pin 7 of the PCF8563. However – it’s an open-drain output – which means current flows from the supply voltage into pin 7. For example if you want to blink an LED, connect a 560Ω resistor between 5V and the anode of the LED, then connect the cathode to pin 7 of the PCF8563.

The frequency is controlled from the register at 0x0D. Simply write one of the following values for the respective frequencies:

• 10000000 for 32.768 kHz;
• 10000001 for 1.024 kHz;
• 10000010 for 32 kHz;
• 10000011 for 1 Hz;
• 0 turns the output off and sets it to high impedance.

The following is a quick demonstration sketch which runs through the options:

// Example 54.2 - PCF8563 square-wave generator (signal from pin 7)

#include "Wire.h"
#define PCF8563address 0x51

void PCF8563oscOFF()
// turns off oscillator
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x0D);
  Wire.write(0);
  Wire.endTransmission();
}

void PCF8563osc1Hz()
// sets oscillator to 1 Hz
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x0D);
  Wire.write(B10000011);
  Wire.endTransmission();
}

void PCF8563osc32Hz()
// sets oscillator to 32 kHz
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x0D);
  Wire.write(B10000010);
  Wire.endTransmission();
}

void PCF8563osc1024kHz()
// sets oscillator to 1.024 kHz
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x0D);
  Wire.write(B10000001);
  Wire.endTransmission();
}

void PCF8563osc32768kHz()
// sets oscillator to 32.768 kHz
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x0D);
  Wire.write(B10000000);
  Wire.endTransmission();
}

void setup()
{
  Wire.begin();
}

void loop()
{
  PCF8563osc1Hz();
  delay(2000);
  PCF8563osc32Hz();
  delay(2000);
  PCF8563osc1024kHz();
  delay(2000);
  PCF8563osc32768kHz();
  delay(2000);
  PCF8563oscOFF();
  delay(2000);
}

And the resulting waveforms from slowest to highest frequency. Note the sample was measured from a point between the LED and resistor, so the oscillations don’t vary between the supply voltage and zero:

Self-awareness of clock accuracy

The PCF8563 monitors the oscillator and supply voltage, and if the oscillator stops or the voltage drops below a certain point – the first bit of the seconds register (called the VL bit) is set to 1. Thus your sketch can tell you if there’s a chance of the time not being accurate by reading this bit. The default value is 1 on power-up, so you need to set it back to zero after setting the time in your sketch – which is done when you write seconds using the code in our example sketches. Then from that point it can be monitored by reading the seconds register, isolating the bit and returning the value.

Examine the function checkVLerror() in the following example sketch. It reads the seconds byte, isolates the VL bit, then turns on D13 (the onboard LED) if there’s a problem. The only way to restore the error bit to “OK” is to re-set the time:

// Example 54.3 - PCF8563 RTC write/read demonstration with error-checking

#include "Wire.h"
#define PCF8563address 0x51

byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
String days[] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };

byte bcdToDec(byte value)
{
  return ((value / 16) * 10 + value % 16);
}

byte decToBcd(byte value){
  return (value / 10 * 16 + value % 10);
}

void setPCF8563()
// this sets the time and date to the PCF8563
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x02);
  Wire.write(decToBcd(second));  
  Wire.write(decToBcd(minute));
  Wire.write(decToBcd(hour));     
  Wire.write(decToBcd(dayOfMonth));
  Wire.write(decToBcd(dayOfWeek));  
  Wire.write(decToBcd(month));
  Wire.write(decToBcd(year));
  Wire.endTransmission();
}

void readPCF8563()
// this gets the time and date from the PCF8563
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x02);
  Wire.endTransmission();
  Wire.requestFrom(PCF8563address, 7);
  second     = bcdToDec(Wire.read() & B01111111); // remove VL error bit
  minute     = bcdToDec(Wire.read() & B01111111); // remove unwanted bits from MSB
  hour       = bcdToDec(Wire.read() & B00111111); 
  dayOfMonth = bcdToDec(Wire.read() & B00111111);
  dayOfWeek  = bcdToDec(Wire.read() & B00000111);  
  month      = bcdToDec(Wire.read() & B00011111);  // remove century bit, 1999 is over
  year       = bcdToDec(Wire.read());
}

void checkVLerror()
// this checks the VL bit in the seconds register
// and turns on D13 if there's a possible accuracy error
{
  byte test;
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x02);
  Wire.endTransmission();
  Wire.requestFrom(PCF8563address, 1);
  test = Wire.read(); 
  test = test & B10000000;
  if (test == B10000000)
  {
    // error
    digitalWrite(13, HIGH);
    Serial.println("Uh-oh - possible accuracy error");
  } else 
  if (test != B10000000)
  {
    digitalWrite(13, LOW);
  }
}

void setup()
{
  Wire.begin();
  pinMode(13, OUTPUT);
  digitalWrite(13, HIGH);
  Serial.begin(9600);
  // change the following to set your inital time
  second = 0;
  minute = 42;
  hour = 11;
  dayOfWeek = 2;
  dayOfMonth = 13;
  month = 8;
  year = 13;
  // comment out the next line and upload again to set and keep the time from resetting every reset
  // setPCF8563();
}

void loop()
{
  readPCF8563();
  Serial.print(days[dayOfWeek]); 
  Serial.print(" ");  
  Serial.print(dayOfMonth, DEC);
  Serial.print("/");
  Serial.print(month, DEC);
  Serial.print("/20");
  Serial.print(year, DEC);
  Serial.print(" - ");
  Serial.print(hour, DEC);
  Serial.print(":");
  if (minute < 10)
  {
    Serial.print("0");
  }
  Serial.print(minute, DEC);
  Serial.print(":");  
  if (second < 10)
  {
    Serial.print("0");
  }  
  Serial.println(second, DEC);  
  checkVLerror();
  delay(1000);
}

And now for a demonstration of the error-checking at work. We have the PCF8563 happily returning the data to the serial monitor. Then the power is removed and restored. You see D13 on the Arduino-compatible board turn on and then the error is displayed in the serial monitor:

This function may sound frivolous, however if you’re building a real product or serious project using the PCF8563, you can use this feature to add a level of professionalism and instil confidence in the end user.

Alarm Clock

You can use the PCF8563 as an alarm clock, that is be notified of a certain time, day and/or day of the week – at which point an action can take place. For example, trigger an interrupt or turn on a digital output pin for an external siren. Etcetera. Using the alarm in the sketch is quite similar to reading and writing the time, the data is stored in certain registers – as shown in the following table from page seven of the data sheet:

However there is a catch – the MSB (most significant bit, 7) in the registers above is used to determine whether that particular register plays a part in the alarm. For example, if you want your alarm to include hours and minutes, bit 7 needs to be set to 1 for the hour and minute alarm register. Don’t panic – you can easily set that bit by using a bitwise OR (“|”) and B10000000 to set the bit on with the matching data before writing it to the register.

Checking if the alarm has occurred can be done with two methods – software and hardware. Using software you check bit 3 of the register at 0x01 (the “AF” alarm flag bit). If it’s 1 – it’s alarm time! Then you can turn the alarm off by setting that bit to zero. Using hardware, first set bit 1 of register 0x01 to 1 – then whenever an alarm occurs, current can flow into pin 3 of the PCF8563. Yes – it’s an open-drain output – which means current flows from the supply voltage into pin 3. For example if you want to turn on an LED, connect a 560Ω resistor between 5V and the anode of the LED, then connect the cathode to pin 3 of the PCF8563. To turn off this current, you need to turn off the alarm flag bit as mentioned earlier.

Now let’s put all that into a demonstration sketch. It’s documented and if you’ve been following along it shouldn’t be difficult at all:

// Example 54.4 - PCF8563 alarm clock demonstration

#include "Wire.h"
#define PCF8563address 0x51

byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
byte alarmMinute, alarmHour, alarmDay, alarmDayOfWeek;
String days[] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };

byte bcdToDec(byte value)
{
  return ((value / 16) * 10 + value % 16);
}

byte decToBcd(byte value){
  return (value / 10 * 16 + value % 10);
}

void setPCF8563alarm()
// this sets the alarm data to the PCF8563
{
  byte am, ah, ad, adow;
  am = decToBcd(alarmMinute);
  am = am | 100000000; // set minute enable bit to on
  ah = decToBcd(alarmHour);
  ah = ah | 100000000; // set hour enable bit to on
  ad = decToBcd(alarmDay);
  ad = ad | 100000000; // set day of week alarm enable bit on
  adow = decToBcd(alarmDayOfWeek);
  adow = ad | 100000000; // set day of week alarm enable bit on

  // write alarm data to PCF8563
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x09);
  Wire.write(am);  
  Wire.write(ah);

  // optional day of month and day of week (0~6 Sunday - Saturday)
  /*
  Wire.write(ad);
  Wire.write(adow);  
  */
  Wire.endTransmission();

  // optional - turns on INT_ pin when alarm activated  
  // will turn off once you run void PCF8563alarmOff()
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x01);
  Wire.write(B00000010);
  Wire.endTransmission();
}

void PCF8563alarmOff()
// turns off alarm enable bits and wipes alarm registers. 
{
  byte test;
  // first retrieve the value of control register 2
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x01);
  Wire.endTransmission();
  Wire.requestFrom(PCF8563address, 1);
  test = Wire.read();

  // set bit 3 "alarm flag" to 0
  test = test - B00001000;

  // now write new control register 2  
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x01);
  Wire.write(test);
  Wire.endTransmission();
}

void checkPCF8563alarm()
// checks if the alarm has been activated
{
  byte test;
  // get the contents from control register #2 and place in byte test;
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x01);
  Wire.endTransmission();
  Wire.requestFrom(PCF8563address, 1);
  test = Wire.read();
  test = test & B00001000; // isolate the alarm flag bit
  if (test == B00001000) // alarm on?
  {
    // alarm! Do something to tell the user
    Serial.println("** alarm **");
    delay(2000);

    // turn off the alarm
    PCF8563alarmOff();
  }
}

void setPCF8563()
// this sets the time and date to the PCF8563
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x02);
  Wire.write(decToBcd(second));  
  Wire.write(decToBcd(minute));
  Wire.write(decToBcd(hour));     
  Wire.write(decToBcd(dayOfMonth));
  Wire.write(decToBcd(dayOfWeek));  
  Wire.write(decToBcd(month));
  Wire.write(decToBcd(year));
  Wire.endTransmission();
}

void readPCF8563()
// this gets the time and date from the PCF8563
{
  Wire.beginTransmission(PCF8563address);
  Wire.write(0x02);
  Wire.endTransmission();
  Wire.requestFrom(PCF8563address, 7);
  second     = bcdToDec(Wire.read() & B01111111); // remove VL error bit
  minute     = bcdToDec(Wire.read() & B01111111); // remove unwanted bits from MSB
  hour       = bcdToDec(Wire.read() & B00111111); 
  dayOfMonth = bcdToDec(Wire.read() & B00111111);
  dayOfWeek  = bcdToDec(Wire.read() & B00000111);  
  month      = bcdToDec(Wire.read() & B00011111);  // remove century bit, 1999 is over
  year       = bcdToDec(Wire.read());
}

void setup()
{
  Wire.begin();
  Serial.begin(9600);
  // change the following to set your initial time
  second = 50;
  minute = 44;
  hour = 13;
  dayOfWeek = 1;
  dayOfMonth = 19;
  month = 8;
  year = 13;
  // comment out the next line and upload again to set and keep the time from resetting every reset
  setPCF8563();

  alarmMinute = 45;
  alarmHour = 13;
  // comment out the next line and upload again to set and keep the alarm from resetting every reset  
  setPCF8563alarm();
}

void loop()
{
  readPCF8563();
  Serial.print(days[dayOfWeek]); 
  Serial.print(" ");  
  Serial.print(dayOfMonth, DEC);
  Serial.print("/");
  Serial.print(month, DEC);
  Serial.print("/20");
  Serial.print(year, DEC);
  Serial.print(" - ");
  Serial.print(hour, DEC);
  Serial.print(":");
  if (minute < 10)
  {
    Serial.print("0");
  }
  Serial.print(minute, DEC);
  Serial.print(":");  
  if (second < 10)
  {
    Serial.print("0");
  }  
  Serial.println(second, DEC);  
  delay(1000);

  // alarm?
  checkPCF8563alarm();
}

This is the same as the example 54.1, however we’ve added the required functions to use the alarm. The required alarm data is stored in the global bytes:

byte alarmMinute, alarmHour, alarmDay, alarmDayOfWeek;

and is written to the PCF8563 using the function:

void setPCF8563alarm()

Note the use of bitwise OR (“|”) to add the enable bit 7 to the data before writing to the register. The interrupt pin is also set to activate at the end of this function, however you can remove that part of the code if unnecessary. We also demonstrate checking the alarm status via software using the function:

void checkPCF8563alarm()

which simply reads the AF bit in the register at 0x01 and let’s us know if the alarm has occurred via the Serial Monitor. In this function you can add code to take action for your required needs. It also calls the function:

void PCF8563alarmOff()

which retrieves the contents of the register at 0x01, sets the AF bit to zero and writes it back. We do this to preserve the status of the other bits in that register. For the curious and non-believers you can see this sketch in action through the following video, first the software and then the hardware interrupt pin method (an LED comes on at the alarm time and is then turned off:

Conclusion

Hopefully you found this tutorial useful and now have the confidence to use the PCF8563 in your own projects. Furthermore I hope you learned something about the I2C bus and can have satisfaction in that you didn’t take the lazy option of using the library. People often say to me “Oh, there’s a library for that”, however if you used every library – you’d never learn how to interface things for yourself. One day there might not be a library! And then where would you be? So learning the hard way is better for you in the long run.

And if you enjoy my tutorials, or want to introduce someone else to the interesting world of Arduino – check out my book (now in a second printing) “Arduino Workshop” from No Starch Press.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

The post Tutorial – Arduino and PCF8563 real time clock IC appeared first on tronixstuff.

Introduction

Time for another instalment in my highly-irregular series of irregular clock projects.  In this we have “Clock Four” – a scrolling text clock. After examining some Freetronics Dot Matrix Displays in the stock, it occurred to me that it would be neat to display the time as it was spoken (or close to it) – and thus this the clock was born. It is a quick project – we give you enough to get going with the hardware and sketch, and then you can take it further to suit your needs.

Hardware

You’ll need three major items – An Arduino Uno-compatible board, a real-time clock circuit or module using either a DS1307 or DS3232 IC, and a Freetronics DMD. You might want an external power supply, but we’ll get to that later on.

The first stage is to fit your real-time clock. If you are unfamiliar with the operation of real-time clock circuits, check out the last section of this tutorial. You can build a RTC circuit onto a protoshield or if you have a Freetronics Eleven, it can all fit in the prototyping space as such:

If you have an RTC module, it will also fit in the same space, then you simply run some wires to the 5V, GND, A4 (for SDA) and A5 (for SCL):

By now I hope you’re thinking “how do you set the time?”. There’s two answers to that question. If you’re using the DS3232 just set it in the sketch (see below) as the accuracy is very good, you only need to upload the sketch with the new time twice a year to cover daylight savings (unless you live in Queensland). Otherwise add a simple user-interface – a couple of buttons could do it, just as we did with Clock Two. Finally you just need to put the hardware on the back of the DMD. There’s plenty of scope to meet your own needs, a simple solution might be to align the control board so you can access the USB socket with ease – and then stick it down with some Sugru:

With regards to powering the clock – you can run ONE DMD from the Arduino, and it runs at a good brightness for indoor use. If you want the DMD to run at full, retina-burning brightness you need to use a separate 5 V 4 A power supply. If you’re using two DMDs – that goes to 8 A, and so on. Simply connect the external power to one DMD’s terminals (connect the second or more DMDs to these terminals):

The Arduino Sketch

You can download the sketch from here. Please use IDE v1.0.1 . The sketch has the usual functions to set and retrieve the time from DS1307/3232 real-time clock ICs, and as usual with all our clocks you can enter the time information into the variables in void setup(), then uncomment setDateDs1307(), upload the sketch, re-comment setDateDs1307, then upload the sketch once more. Repeat that process to re-set the time if you didn’t add any hardware-based user interface.

Once the time is retrieved in void loop(), it is passed to the function createTextTime(). This function creates the text string to display by starting with “It’s “, and then determines which words to follow depending on the current time. Finally the function drawText() converts the string holding the text to display into a character variable which can be passed to the DMD.

And here it is in action:

Conclusion

This was a quick project, however I hope you found it either entertaining or useful – and another random type of clock that’s easy to reproduce or modify yourself. We’re already working on another one which is completely different, so stay tuned.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

The post Project: Clock Four – Scrolling text clock appeared first on tronixstuff.