Tutorial – Arduino and MC14489 LED Display Driver

Learn how to use MC14489 LED display driver ICs with Arduino in chapter fifty-one of a series originally titled “Getting Started/Moving Forward with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

Updated 12/05/2013

Introduction

Recently we’ve been looking at alternatives to the MAX7219 LED display driver IC due to pricing and availability issues (stay tuned for that one) – and came across an old but still quite useful IC – the MC14489 from Motorola (now Freescale Semiconductor). The MC14489 can drive five seven-segment LED numbers with decimal point, or a combination of numbers and separate LEDs. You can also daisy-chain more than one to drive more digits, and it’s controlled with a simple serial data-clock method in the same way as a 74HC595 shift register. Sourcing the MC14489 isn’t too difficult – it’s available from element14, Newark, Digikey, and so on – or if you’re not in a hurry, try the usual suspects like Futurlec.

For the purpose of the tutorial we’ll show you how to send commands easily from your Arduino or compatible board to control a five-digit 7-segment LED display module - and the instructions are quite simple so they should translate easily to other platforms. Once you have mastered the single module, using more than one MC14489 will be just as easy. So let’s get started.

Hardware

Before moving forward, download the data sheet (pdf). You will need to refer to this as you build the circuit(s). And here’s our subject in real life:

For our demonstration display we’ll be using a vintage HP 5082-7415 LED display module. However you can use almost any 7-segment modules as long as they’re common-cathode - for example, Sparkfun part number COM-11405. If you’re using a four-digit module and want an extra digit, you can add another single digit display. If you want a ruler, the design files are here.

Connecting the MC14489 to an LED display isn’t complex at all. From the data sheet consider Figure 9 (click the image to enlarge):

Each of the anode control pins from the MC14489 connect to the matching anodes on your display module, and the BANK1~5 pins connect to the matching digit cathode pins on the display module. You can find the MC14489 pin assignments on page 1 of the data sheet. Seeing as this is chapter fifty-one  - by now you should be confident with finding such information on the data sheets, so I will be encouraging you to do a little more of the work.

Interesting point – you don’t need current-limiting resistors. However you do need the resistor Rx – this controls the current flow to each LED segment. But which value to use? You need to find out the forward current of your LED display (for example 20 mA) then check Figure 7 on page 7 of the data sheet (click image to enlarge):

To be conservative I’m using a value of 2k0 for Rx, however you can choose your own based on the data sheet for your display and the graph above.  Next – connect the data, clock and enable pins of the MC14489 to three Arduino digital pints – for our example we’re using 5, 6 and 7 for data, clock and enable respectively. Then it’s just 5V and GND to Arduino 5V and GND – and put a 0.1uF capacitor between 5V and GND. Before moving on double-check the connections – especially between the MC14489 and the LED display.

Controlling the MC14489

To control the display we need to send data to two registers in the MC14489 – the configuration register  (one byte) and the display register (three bytes). See page 9 of the data sheet for the overview. The MC14489 will understand that if we send out one byte of data it is to send it the configuration register, and if it receives three bytes of data to send it to the display register. To keep things simple we’ll only worry about the first bit (C0) in the configuration register – this turns the display outputs on or off. To do this, use the following:

 digitalWrite(enable, LOW);
 shiftOut(data, clock, MSBFIRST, B00000001); // used binary for clarity, however you can use decimal or hexadecimal numbers
 digitalWrite(enable, HIGH);
 delay(10);

and to turn it off, send bit C0 as zero. The small delay is necessary after each command.

Once you have turned the display on – the next step is to send three bytes of data which represent the numbers to display and decimal points if necessary. Review the table on page 8 of the data sheet. See how they have the binary nibble values for the digits in the third column. Thankfully the nibble for each digit is the binary value for that digit. Furthermore you might want to set the decimal point – that is set using three bits in the first nibble of the three bytes (go back to page 9 and see the display register). Finally you can halve the brightness by setting the very first bit to zero (or one for full brightness).

As an example for that – if you want to display 5.4321 the three bytes of data to send in binary will be:

1101 0101 0100 0011 0010 0001

Let’s break that down. The first bit is 1 for full brightness, then the next three bits (101) turn on the decimal point for BANK5 (the left-most digit). Then you have five nibbles of data, one for each of the digits from left to right. So there’s binary for 5, then four, then three, then two, then one.

 digitalWrite(enable, LOW); 
 shiftOut(data, clock, MSBFIRST, B11010101); // D23~D16 
 shiftOut(data, clock, MSBFIRST, B01000011); // D15~D8
 shiftOut(data, clock, MSBFIRST, B00100001); // D7~D0
 digitalWrite(enable, HIGH);
 delay(10);

To demonstrate everything described so far, it’s been neatly packaged into our first example sketch – Example 51.1:

// Example 51.1
// Motorola MC14489 with HP 5082-7415 5-digit, 7-segment LED display
// 2k0 resistor on MC14489 Rx pin
// John Boxall 2013 CC by-sa-nc

// define pins for data from Arduino to MC14489
// we treat it just like a 74HC595
int data = 5;
int clock = 6;
int enable = 7;

void setup()
{
 pinMode(data, OUTPUT);
 pinMode(enable, OUTPUT);
 pinMode(clock, OUTPUT);
 displayOn(); // display defaults to off at power-up
}

void displayTest1()
// displays 5.4321
{
 digitalWrite(enable, LOW); // send 3 bytes to display register. See data sheet page 9
 // you can also insert decimal or hexadecimal numbers in place of the binary numbers
 // we're using binary as you can easily match the nibbles (4-bits) against the table
 // in data sheet page 8
 shiftOut(data, clock, MSBFIRST, B11010101); // D23~D16 
 shiftOut(data, clock, MSBFIRST, B01000011); // D15~D8
 shiftOut(data, clock, MSBFIRST, B00100001); // D7~D0
 digitalWrite(enable, HIGH);
 delay(10);
}

void displayTest2()
// displays ABCDE
{
 digitalWrite(enable, LOW); // send 3 bytes to display register. See data sheet page 9
 // you can also insert decimal or hexadecimal numbers in place of the binary numbers
 // we're using binary as you can easily match the nibbles (4-bits) against the table
 // in data sheet page 8
 shiftOut(data, clock, MSBFIRST, B10001010); // D23~D16 
 shiftOut(data, clock, MSBFIRST, B10111100); // D15~D8
 shiftOut(data, clock, MSBFIRST, B11011110); // D7~D0
 digitalWrite(enable, HIGH);
 delay(10);
}

void displayOn()
// turns on display
{
 digitalWrite(enable, LOW);
 shiftOut(data, clock, MSBFIRST, B00000001);
 digitalWrite(enable, HIGH);
 delay(10);
}

void displayOff()
// turns off display
{
 digitalWrite(enable, LOW);
 shiftOut(data, clock, MSBFIRST, B00000000);
 digitalWrite(enable, HIGH);
 delay(10);
}

void loop()
{
 displayOn();
 displayTest1();
 delay(1000);
 displayTest2();
 delay(1000);
 displayOff();
 delay(500);
}

… with the results in the following video:

Now that we can display numbers and a few letters with binary, life would be easier if there was a way to take a number and just send it to the display.

So consider the following function that takes an integer between 0 and 99999, does the work and sends it to the display:

void displayIntLong(long x)
// takes a long between 0~99999 and sends it to the MC14489
{
 int numbers[5];
 byte a=0; 
 byte b=0; 
 byte c=0; // will hold the three bytes to send to the MC14489 

 // first split the incoming long into five separate digits
 numbers[0] = int ( x / 10000 ); // left-most digit (will be BANK5)
 x = x % 10000; 
 numbers[1] = int ( x / 1000 );
 x = x % 1000; 
 numbers[2] = int ( x / 100 );
 x = x % 100; 
 numbers[3] = int ( x / 10 );
 x = x % 10; 
 numbers[4] = x % 10; // right-most digit (will be BANK1)

 // now to create the three bytes to send to the MC14489
 // build byte c which holds digits 4 and 5
 c = numbers[3];
 c = c << 4; // move the nibble to the left
 c = c | numbers[4];
 // build byte b which holds digits 3 and 4
 b = numbers [1];
 b = b << 4;
 b = b | numbers[2];
 // build byte a which holds the brightness bit, decimal points and digit 1
 a = B10000000 | numbers[0]; // full brightness, no decimal points

 // now send the bytes to the MC14489
 digitalWrite(enable, LOW);
 shiftOut(data, clock, MSBFIRST, a);
 shiftOut(data, clock, MSBFIRST, b);
 shiftOut(data, clock, MSBFIRST, c); 
 digitalWrite(enable, HIGH);
 delay(10); 
}

So how does that work? First it splits the 5-digit number into separate digits and stores them in the array numbers[]. It then places the fourth digit into a byte, then moves the data four bits to the left – then we bitwise OR the fifth digit into the same byte. This leaves us with a byte of data containing the nibbles for the fourth and fifth digit. The process is repeated for digits 2 and 3. Finally the brightness bit and decimal point bits are assigned to another byte which then has the first digit’s nibble OR’d into it. Which leaves us with bytes a, b and c ready to send to the MC14489. Note that there isn’t any error-checking – however you could add a test to check that the number to be displayed was within the parameter, and if not either switch off the display (see example 51.1) or throw up all the decimal points or … whatever you want.

You can download the demonstration sketch for the function – Example 51.2, and view the results in the following video:

You can also display the letters A to F by sending the values 10 to 15 respectivel to each digit’s nibble. However that would be part of a larger application, which you can (hopefully) by now work out for yourself. Furthermore there’s some other characters that can be displayed – however trying to display the alphabet using 7-segment displays is somewhat passé. Instead, get some 16-segment LED modules or an LCD.

Finally, you can cascade more than one MC14489 to control more digits. Just run a connection from the data out pin on the first MC14889 to the data pin of the second one, and all the clock and enable lines together. Then send out more data – see page 11 of the data sheet. If you’re going to do that in volume other ICs may be a cheaper option and thus lead you back to the MAX7219.

Conclusion

For a chance find the MC14489 is a fun an inexpensive way to drive those LED digit displays. We haven’t covered every single possible option or feature of the part – however you will now have the core knowledge to go further with the MC14489 if you need to move further with it. And if you enjoy my tutorials, or want to introduce someone else to the interesting world of 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.

Arduino and KTM-S1201 LCD modules

Learn how to use very inexpensive KTM-S1201 LCD modules in this edition of our Arduino tutorials. This is chapter forty-nine of a series originally titled “Getting Started/Moving Forward with Arduino!” by John Boxall – A tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here.

Introduction

After looking for some displays to use with another (!) clock, I came across some 12-digit numeric LCD displays. They aren’t anything flash, and don’t have a back light –  however they were one dollar each. How could you say no to that? So I ordered a dozen to try out. The purpose of this tutorial is to show you how they are used with an Arduino in the simplest manner possible.

Moving forward – the modules look like OEM modules for desktop office phones from the 1990s:

With a quick search on the Internet you will find a few sellers offering them for a dollar each. The modules (data sheet) use the NEC PD7225 controller IC (data sheet):

They aren’t difficult to use, so I’ll run through set up and operation with a few examples.

Hardware setup

First you’ll need to solder some sort of connection to the module – such as 2×5 header pins. This makes it easy to wire it up to a breadboard or a ribbon cable:

The rest of the circuitry is straight-forward. There are ten pins in two rows of five, and with the display horizontal and the pins on the right, they are numbered as such:

Now make the following connections:

• LCD pin 1 to 5V
• LCD pin 2 to GND
• LCD pin 3 to Arduino D4
• LCD pin 4 to Arduino D5
• LCD pin 5 to Arduino D6
• LCD pin 6 to Arduino D7
• LCD pin 7 – not connected
• LCD pin 8 – Arduino D8
• LCD pin 9 to the centre pin of a 10k trimpot – whose other legs connect to 5V and GND. This is used to adjust the contrast of the LCD.

The Arduino digital pins that are used can be changed – they are defined in the header file (see further on). If you were curious as to how low-current these modules are:

That’s 0.689 mA- not bad at all. Great for battery-powered operations. Now that you’ve got the module wired up, let’s get going with some demonstration sketches.

Software setup

The sketches used in this tutorial are based on work by Jeff Albertson and Robert Mech, so kudos to them – however we’ve simplified them a little to make use easier. We’ll just cover the functions required to display data on the LCD. However feel free to review the sketches and files along with the controller chip datasheet as you’ll get an idea of how the controller is driven by the Arduino.

When using the LCD module you’ll need a header file in the same folder as your sketch. You can download the header file from here. Then every time you open a sketch that uses the header file, it should appear in a tab next to the main sketch, for example (click to enlarge):

There’s also a group of functions and lines required in your sketch. We’ll run through those now – so download the first example sketch, add the header file and upload it. Your results should be the same as the video below:

So how did that work? Take a look at the sketch you uploaded.  You need all the functions between the two lines of “////////////////////////” and also the five lines in void setup(). Then you can display a string of text or numbers using

ktmWriteString();

which was used in void loop(). You can use the digits 0~9, the alphabet (well, what you can do with 7-segments), the degrees symbol (use an asterix – “*”) and a dash (use  - “-”). So if your sketch can put together the data to display in a string, then that’s taken care of.

If you want to clear the screen, use:

 ktmCommand(_ClearDsp);

Next – to individually place digits on the screen, use the function:

 ktmPrnNumb(n,p,d,l);

Where n is the number to be displayed (zero or a positive integer), p is the position on the LCD for the number’s  (the positions from left to right are 11 to 0…), d is the number of digits to the right of the decimal point (leave as zero if you don’t want a decimal point), and l is the number of digits being displayed for n. When you display digits using this function you can use more than one function to compose the number to be displayed – as this function doesn’t clear the screen.

To help get your head around it, the following example sketch (download) has a variety of examples in void loop(). You can watch this example in the following video:

Conclusion

So there you have it – an incredibly inexpensive and possibly useful LCD module. Thank you to Jeff Albertson and Robert Mech for their help and original code.

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.

Project: Clock One

Let‘s make a huge analogue and digital clock using a dot-matrix display. 

Updated 18/03/2013

For some strange reason I have a fascination with various types of electronic clocks (which explains this article). Therefore this project will be the start of an irregular series of clock projects whose goal will be easy to follow and produce interesting results. Our “Clock One” will use a Freetronics Dot Matrix Display board as reviewed previously. Here is an example of an operating Clock One:

As you can see, on the left half of the board we have a representation of an analogue clock. Considering we only have sixteen rows of sixteen LEDs, it isn’t too bad at all. The seconds are illuminated by sixty pixels that circumnavigate the square clock throughout the minute. On the right we display the first two letters of the day of the week, and below this the date. In the example image above, the time is 6:08. We omitted the month – if you don’t know what month it is you have larger problems.

Hardware

To make this happen you will need:

• A Freetronics Dot Matrix Display board;
• If you want the run the display at full brightness (ouch!) you will need a 5V 2.8A power supply – however our example is running without the external supply and is pretty strong
• An Arduino board of some sort, an Uno or Eleven is a good start
• A Maxim DS1307 real-time clock IC circuit. How to build this is explained here. If you have a Freetronics board, you can add this circuit directly onto the board!

Software

Planning the clock was quite simple. As we can only draw lines, individual pixels, and strings of text or individual characters, some planning was required in order to control the display board. A simple method is to use some graph paper and note down where you want things and the coordinates for each pixel of interest, for example:

Using the plan you can determine where you want things to go, and then the coordinates for pixels, positions of lines and so on. The operation for this clock is as follows:

• display the day of week
• display the date
• draw the hour hand
• draw the minute hand
• then turn on each pixel representing the seconds
• after the 59th second, turn off the pixels on the left-hand side of the display (to wipe the clock face)

There isn’t a need to wipe the right hand side of the display, as the characters have a ‘clear’ background which takes care of this when updated. At this point you can download the Arduino sketch from here. Note that the sketch was written to get the job done and ease of reading and therefore not what some people would call efficient. Some assumed knowledge is required – to catch up on the use of the display, see here; and for DS1307 real-time clock ICs, see here.

The sketch uses the popular method of reading and writing time data to the DS1307 using functions setDateDs1307 and getDateDs1307. You can initally set the time within void setup() – after uploading the sketch, comment out the setDateDs1307 line and upload the sketch again, otherwise every time the board resets or has a power outage the time will revert to the originally-set point.

Each display function is individual and uses many switch…case statements to determine which line or pixel to draw. This was done again to draw the characters on the right due to function limitations with the display library. But again it works, so I’m satisfied with it. You are always free to download and modify the code yourself.  Moving forward, here is a short video clip of the Clock One in action:

For more information about the display used, please visit the Freetronics product page. Disclaimer – The display module used in this article is a promotional consideration made available by Freetronics.

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.

Learn to solder with David L. Jones!

Hello Readers

How is your soldering? Have you always wanted to improve your soldering skills, or never heated an iron in your life and didn’t know where to start? No matter your level of skill you could do a lot worse than review the following video blogs in this article by David L. Jones.

Who? 

[David] shares some of his 20 years experience in the electronics design industry in his unique non-scripted naturally overly enthusiastic and passionate style.
Bullsh!t and political correctness don’t get a look-in.

Dave started out in hobby electronics over 30 years ago and since then has worked in such diverse areas as design engineering, production engineering, test engineering, electro-mechanical engineering, that wacky ISO quality stuff, field service, concept design, underwater acoustics, ceramic sensors, military sonar systems, red tape, endless paperwork trails, environmental testing, embedded firmware and software application design, PCB design (he’s CID certified), power distribution systems, ultra low noise and low power design, high speed digital design, telemetry systems, and too much other stuff he usually doesn’t talk about.

He has been published in various magazines including: Electronic Today International, Electronics Australia, Silicon Chip, Elektor, Everyday Practical Electronics (EPE), Make, and ReNew.

Few people know Dave is also a world renowned expert and author on Internet Dating, a qualified fitness instructor, geocacher, canyoner, and environmentalist.

Regular readers of this website would know that I rarely publish outside material – however the depth and quality of the tutorials make them a must-see for beginners and experienced people alike. Furthermore, if you have the bandwidth they can be viewed in 1080p. And as a fellow Australian I’m proud to support Dave and his efforts. So I hope you can view, enjoy and possibly learn from the following videos:

The first covers the variety of tools you would use:

And the second covers through-hole PCB soldering:

The third covers surface-mount soldering:

Finally, watch the procedure for soldering a tiny SMD IC using the ‘dead bug’ method:

And for something completely different:

If you enjoyed those videos then don’t forget to check out what’s new on Dave’s eevblog website and forum. Videos shown are (C) David L. Jones 2011 and embedded with permission.

As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts, follow on twitter, facebook, or join our Google Group.

[Disclaimer - I really enjoy the content at eevblog.com]

Otherwise, have fun, be good to each other – and make something! 

Kit review – Evil Mad Science Larson Scanner

Hello readers

Time yet again for another kit review. Today’s kit is the Larson Scanner from Evil Mad Science. What a different name for a company; their byline is “DIY and open source hardware for art, education and world domination”. Art? Yes. Education? Definitely. World domination? Possibly – you could use the blinking LEDs to hypnotise the less intelligent world leaders out there.

Anyhow, what is a Larson Scanner? Named in honour of Glen A. Larson the creator of television shows such as Battlestar Galactica and Knight Rider – as this kit recreates the left and right blinking motion used in props from those television shows. For example:

The kit itself is quite inexpensive, easy to assemble – yet can be as complex as you want it to be. More about that later, for now let’s put one together and see how it performs. There are two versions of the kit, one with 5mm clear LEDs and our review model with 10mm diffused red LEDs. The kit arrives inside a huge resealable anti-static bag, as such:

Upon opening the bag we have the following parts (there was an extra LED and resistor, thanks):

… the PCB:

… which is nicely done with a good silk-screen and solder mask. And finally:

A very handy item – a battery box with power switch. The kit is powered by 2 x AA cells (not included!). And finally, the instructions:

At this point you can see that this kit is designed for the beginner in mind. The instructions are easy to read, clear, and actually very well done. If you are looking for a kit to get someone interested in electronics and to practice their soldering, you could do a lot worse than use this kit.

Construction was very easy, starting with the resistors:

followed by the capacitor and button:

then the microcontroller:

… no IC socket. For a beginners’ kit, perhaps one should have been included. Next was the battery box. Some clever thinking has seen holes in the PCB to run the wires through before soldering into the board – doing so provides a good strain relief for them:

… and finally the LEDs. Beginners may solder them in one at a time:

however it is quicker to line them up all at once than solder in one batch:

… which leaves us with the final product:

Operation is very simple – the power switch is on the battery box. The button on the PCB controls the speed of LED scrolling, and if held down switches the brightness between low and high. Now for some action video of the Larson Scanner in operation:

Well that really was fun, a nice change from the usual things around here.

But wait, there’s more… although the Larson Scanner is a good training kit, it can also function in other interesting ways. The kit is completely open-source, you can download the PCB layout file, circuit schematic and microcontroller code. Get two or more and link them together to make a really wide LED display – expansion instructions are available from here. If you solder in a 6-pin PCB header to the area marked J1 on the PCB, you can reprogram the microcontroller using an STK500-compatible programmer.

After sitting my Larson Scanner next to the computer tower for a few minutes, I had contemplated fitting it into a 5.25″ drive bay to make my own Cylon PC, however that might be a little over the top. However my PC case has some dust filters on the front, which would allow LEDs to shine through in a nicely subdued way. Mounting the Larson Scanner PCB inside the computer case will be simple, and power can be sourced from the computer power supply – 5V is available from a disk drive power lead.

If you are going to modify your PC in a similar fashion, please read my disclaimer under “boring stuff” first.

The Larson Scanner can run on 3.3V without any alteration to the supplied components. What needs to be done is to use a voltage regulator to convert the 5V down to 3.3V. My example has used a 78L33 equivalent, the TI LP2950 as it is in stock. The power comes from a drive power cable splitter as such:

You may have a spare power plug in your machine, so can tap from that. 5V is the red lead, and GND is the adjacent black lead. Don’t use yellow – it is 12V. It is then a simple matter of running 5V from the red lead to pin 1 of the regulator, GND from the Larson Scanner and PC together to pin 2, and 3.3V out from the regulator to the PCB 3.3V. Insulation is important with this kind of work, so use plenty of heatshrink:

… then cover the whole lot up:

Now to locate a free power plug in the machine. It has been a while since opening the machine – time for a dust clean up as well:

Mounting the PCB is a temporary affair until I can find some insulated mounting  standoffs:

However it was worth the effort, the following video clip shows the results in action:

So there you have it. The Larson Scanner is an ideal kit for the beginner, lover of blinking LEDs, and anyone else that wants to have some easy blinking fun. You can buy Larson Scanner kits in Australia from Little Bird Electronics, or directly from Evil Mad Science for those elsewhere.

As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts, follow me on twitter or facebook, or join our Google Group for further discussion.

High resolution images are available on flickr.

[Note - The kit was purchased by myself personally and reviewed without notifying the manufacturer or retailer]

Otherwise, have fun, be good to each other – and make something!

Kit review – Freeduino v1.22 Arduino-compatible

Hello readers

Time again for another kit review. Today we will examine the Freeduino Arduino Duemilanove-compatible board in a kit. It is always interesting to see how the different types and makes of Arduino-compatible boards present themselves, so this is review is an extension of that curiosity. This kit was originally designed by NKC Electronics and released under a Creative Commons license.

The packaging can either be classed as underwhelming or environmentally-friendly, as the kit arrives in several plastic resealable bags. Upon emptying them out we are presented with the following, the parts:

and the PCB:

Hopefully you noticed what ends up being the key features of this kit – the pre-soldered FTDI IC and mini-USB socket. This means the Freeduino can be used with a USB cable (not included) and not an expensive FTDI cable. The PCB itself is very solid, has a very descriptive silk-screen layer with all the component positions labelled, is solder-masked, and has nice rounded corners.

Reviewing the included parts did make me wonder why the supplier has used 5% carbon-film resistors and ceramic capacitors instead of polyesters (except for one). It turns out that Seeedstudio (the distributor for my example kit) claim 5% resistors are easier to read. Originally I claimed that this was an excuse to save a few cents, however a few people have said that such resistors are easier to read.

Furthermore, this one missed out on the polyfuse for USB overcurrent and short-circuit protection. And whether or not the larger tolerances affect the operation of the board, the cheaper components make the finished product look very 1977. However on a brighter note, an IC socket is included.

Assembly was quick and simple. There are excellent online instructions published by the Freeduino creator NKC available here. However you can also follow the silk-screen labels on the PCB as well. A good method is to start with the lowest-profile compontents, such as resistors and capacitors:

… then followed by the capacitors, crystal, LEDs and reset button:

Notice how the ceramic capacitors lead-spacing is too narrow for the holes on the PCB – this makes me think that the distributor has skimped out on the final product and been too lazy to update the PCB layout. The ATmega168 label is an example of this. Moving forward, the voltage regulator and sockets. The easiest way to solder in the shield sockets is to place them into the pins of an Arduino shield and solder – as such:

And there you have it, one Freediono v1.22 Arduino Duemilanove-compatible board:

The image above also displays another bugbear with this kit – the LED placement. When you have a shield inserted, all of the LEDs are covered up. Furthermore, unlike other Arduino board kits (such as the Freetronics KitTen) you are stuck with the maximum current output of 50mA for the 3.3V rail as there isn’t a dedicated 3.3V voltage regulator on board. Finally, the power switching between USB and the DC socket is controlled with a jumper and header pins between the USB socket and the 7805 voltage regulator.

Although I might have sounded a little harsh about this kit, it is relatively inexpensive, easy to assemble, and has the USB interface onboard. These are all good things. However the PCB layout could have been improved by correctly spacing the holes for the ceramic capacitors, and moving the LEDs to the end of the board so they are visible with shields inserted. What’s the point of having all those LEDs if you cannot see them…

So if you really get the urge to make your own board with the USB interface, or want to give someone some reasonable soldering practice, this isn’t a bad choice at all. Otherwise get a KitTen or save time and buy an Eleven.

As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts, follow me on twitter or facebook, or join our Google Group for further discussion.

High resolution images are available on flickr.

[Note - The kit was purchased by myself personally and reviewed without notifying the manufacturer or retailer]

Otherwise, have fun, be good to each other – and make something!

The DFRobot LCD4884 LCD Shield

Learn how to use the DFRobot LCD4884 Arduino LCD shield.

Updated 19/03/2013

This needs to be updated for use with Arduino IDE v1.0.1 and greater… however I can’t locate my shield to test it. Stay tuned via twitter to find out when this is updated.

This article is my response to a request on how to use the LCD4884 LCD shield from DFRobot in China. It is a simple way of displaying text and the odd graphic, as well as another way to accept user input. Here is the shield in question:

From a hardware perspective the LCD has a resolution of 84 by 48 pixels, with a blue back light. It can easily display six rows of fourteen alphanumeric characters, or two rows of six very large characters. Furthermore, it can display bitmap images that are appropriately sized. At the top-left of the shield digital pins eight to thirteen have been expanded with matching Vcc and GND pins, and at the bottom right the same has been done with analogue pins one through to five. Therefore if using this shield, you will lose digital pins two through to seven and analogue zero.

Along the bottom-left of the shield are solder pads for some other I/O options, however I couldn’t find any documentation on how these are used. Below the LCD is a small four-way joystick that also has an integral button. This is connected to analog pin zero via a resistor network. This joystick can be used for user input and also to create some nifty menu systems. To the right is a power-on LED which is really too bright, I would recommend sanding it a little to reduce the intensity, or just melting it off with a soldering iron.

The shield requires an Arduino library which can be downloaded from the shield’s wiki page. There is also a good demonstration sketch on the wiki, however some of our readers may find this to be somewhat complex. Therefore where possible I will break down and explain the functions in order to simplify use of the shield, then use them in a demonstration sketch.

Controlling the backlight is very easy, just use digitalWrite(7, HIGH/LOW) to turn it on and off. Don’t forget to put pinMode(7, OUTPUT) in void setup();.

Reading the joystick position is accomplished via analogRead(0);. It returns the following values as such:

• Up – 505
• Down – 0
• Left – 740
• Right – 330
• pressed in – 144
• Idle (no action) – 1023

By using analogRead(0) and if… statements you can read the joystick in a simple way. Don’t forget to allow for some tolerance in the readings. Attempts to press the button while forcing a direction did not return any different values. In the example sketch later on, you can see how this is implemented. Always remember to insert:

lcd.LCD_init();

in void setup() to create an instance of the LCD, and

#include <LCD4884.h>

at the start of your sketch to enable the library.

Now to display text on the LCD. Here is an example of the standard font text:

Using the standard font, we can position text using the following function:

lcd.LCD_write_string(x,y,"insert text here", MENU_NORMAL); // ignore MENU_NORMAL for now

The parameter x is for the x-coordinate of the first character – measured in pixels, not characters. However y is the coordinate in character lines (!). The screen can display six lines of fourteen characters. To display the larger font, for example:

use the following:

lcd.LCD_write_string_big(x,y, "012345", MENU_NORMAL);

Unfortunately the library only supports the digits 0~9, +, – and decimal point. You can modify the file font_big.h in the library folder and create your own characters. Once again the x parameter is the number of pixels across to place the first character, and y is 0 for the top line and 3 for the bottom line. Notice that the characters in this font are proportional, however the maximum number of digits to plan for in one line would be six.

To clear the display, use:

lcd.LCD_clear();

By now you will be able to display text, control the backlight and read the joystick. The following demonstration sketch (download) puts it all together so far:

#include <LCD4884.h>

int z=0;

int dd=200;

void setup()

{

lcd.LCD_init(); // creates instance of LCD

lcd.LCD_clear(); // blanks the display

pinMode(7, OUTPUT);

}

void loop()

{  // first some text display

for (int a=0; a<5; a++)

{

digitalWrite(7, LOW);

delay(300);

digitalWrite(7, HIGH);

delay(300);

}

for (int a=0; a<6; a++)

{

lcd.LCD_write_string(0,a,"01234567980123", MENU_NORMAL); // ignore MENU_NORMAL for now

delay(dd);

}

delay(dd);

lcd.LCD_clear();   // blanks the display

delay(500);

lcd.LCD_write_string_big(0, 0, "012345", MENU_NORMAL);

lcd.LCD_write_string_big(0, 3, "-+-+-+", MENU_NORMAL);

delay(1000);

lcd.LCD_clear();  // now to read the joystick using analogRead(0). Press RESET whien finished

do

{

z=analogRead(0);

if (z==0)

{

lcd.LCD_write_string(2,2,"Down", MENU_NORMAL);

}     else

if (z>0 && z<150)

{

lcd.LCD_write_string(2,2,"OK   ", MENU_NORMAL);

delay(dd);

}       else

if (z>150 && z<350)

{

lcd.LCD_write_string(2,2,"Right", MENU_NORMAL);

delay(dd);

}         else

if (z>350 && z<510)

{

lcd.LCD_write_string(2,2,"Up   ", MENU_NORMAL);

delay(dd);

}         else

if (z>510 && z<750)

{

lcd.LCD_write_string(2,2,"Left ", MENU_NORMAL);

delay(dd);

}           else

if (z>750)

{

lcd.LCD_write_string(2,2,"nil  ", MENU_NORMAL);

delay(dd);

}

}  while (1>0);

}

Next is to create and display bitmap images. Images can be up to 84 x 48 pixels in size. There are no shades of grey in the images, just pixels on or off. To display a bitmap is a convoluted process but can be mastered. We need to convert a bitmap image into hexadecimal numbers which are then stored in a text file for inclusion into the sketch. To do so, follow these steps:

Create your monochrome image using an editor such as Gimp. Make sure your file name ends with .bmp. Such as:

Next, download the BMP2ASM program from this website. [Sorry, could only find a Windows version]. Open your .bmp file as created above, and you will see a whole bunch of hexadecimal numbers at the bottom of the window:

Turn on the check boxes labelled “Stretch”, “Use Prefix” and “Use suffix”. Then click “Convert”. Have a look in your folder and you will find a text file with an extension .asm. Open this file in a text editor such as Notepad. Remove all the instances of “dt”, as well as the top line with the file path and name. Finally, put commas at the end of each line.

You should now be left with a file of hexadecimal numbers. Encase these numbers in the form of an array as such:

What we have done is places the hexadecimal numbers inside the

unsigned char hellobmp[]= {}

declaration. To make life simpler, ensure the filename (ending with .h) is the same as the variable name, as in this example it is called hellobmp(.h). And make sure you have saved this file in the same folder as the sketch that will use it.

Finally, we include the hellobmp.h file in our example sketch to display the image:

#include "LCD4884.h"

#include "hellobmp.h" // this file needs to be in the same folder as your sketch

void setup()

{

  lcd.LCD_init(); // creates instance of LCD

  lcd.LCD_clear(); // blanks the display

}

void loop()

{

   lcd.LCD_draw_bmp_pixel(0,0, hellobmp, 84,48);

   do { } while (1>0); // do nothing

}

Notice in the function lcd.LCD_draw_bmp_pixel the filename hellobmp is the same as in the #include declaration is the same as the hellobmp.h file we created. They all need to match. Furthermore, the four numerical parameters are the bitmap’s top-left x-y and bottom-right x-y coordinates on the LCD. So after all that, here is the result:

So there you have it. If you have any questions about this LCD shield contact DF Studio, or ask a question in our Google Group.

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.

Kit Review – adafruit industries Ice Tube clock v1.1

Hello readers

Today we examine a kit that perhaps transcends from general electronic fun and games into the world of modern art – the adafruit “Ice Tube” clock.

What is an Ice Tube clock? Before LCDs (liquid-crystal displays) were prevalent another form of display technology was popular – the vacuum-fluorescent display (or VFD). This clock uses a VFD originally manufactured in the former Soviet Union (link for the kids) or Russia (I think mine is date-stamped January 1993). This particular VFD contains a series of seven-segment digits and a dot, which allow the display of time in a bright and retro fashion.

Since this kit was released I had always desired one, however my general parsimonious traits and the wavering exchange rate against the US dollar kept my spending in check. But lately my wallet was hit by a perfect storm: the Australian dollar hit parity with the greenback, adafruit had a discount code and I felt like spending some money – so before the strange feelings passed I ordered a kit post-haste.

Sixteen slow, hot days later the box arrived. I must admit to enjoying a good parcel-opening:

As always, the packaging was excellent and everything arrived as it should have. But what was everything?

Included is the anti-static bag containing the PCB and general components, a bag with the laser-cut acrylic pieces to assemble the housing, another bag with the housing fasteners and the back-up coin cell for the clock, a mains adaptor, and finally another solid cardboard box containing the classic display unit – albeit with the following sensible warning:

And finally the Russian IV-18 display tube:

The tube is a fascinating piece of work, certainly a piece of perfect retro-technology and a welcome addition to my household. Assembling the clock will not be a fast process, and in doing so I recommend reviewing the detailed instructions several times over at the adafruit website. Furthermore, it is a good idea to identify, measure and line up the components ready for use, to save time and confusion along the way. Your experience may vary, however this kit took around three hours for me to construct.

Normally with most kits you can just solder the components in any order, however it is recommended you follow the instructions, as they are well written and allow for testing along the way. For example, after installing the power regulator, you can check the output:

At this stage, you can test your progress with the piezo beeping at power-on:

These mid-construction tests are a good idea as you can hopefully locate any problems before things get out of hand. Another item to be careful with is the PLCC socket for the Maxim MAX6921 VFD driver IC (second from the left):

However with time and patience there is no reason why you would have any problems. Once the main PCB is completed, the next item is the end PCB which connects to the VFD:

At this point it is a good time to have a break and a bit of a stretch, as you need all your patience for soldering in the VFD. Before attempting to do so, try and carefully straighten all the wires from the VFD so they are parallel with each other. Then using the adafruit instructions, make sure you have the tube wires lined up with the correct hole on the PCB:

After I had the leads through the correct holes on the PCB, trimming the leads made things easier:

It is also a good idea to check the gap between the VFD and the PCB is correct, by checking the fit within the housing:

And after much patience, wire pulling with pliers, and light soldering –  the VFD was married to the PCB:

So now the difficult soldering work has been completed and now it was time for another test – the big one… does it all work?

Yes, yes it does. *phew* The low brightness is normal, as that is the default level set by the software. Please note: if you run your VFD without an enclosure that you must be careful of the high voltages on the right-hand side of the PCB and also the VFD PCB. If you test your VFD in this manner, don’t forget to allow ten minutes for the voltage to return to a safe level after removing the power supply. If you have been following the instructions (I hope so!) there is some more soldering to do, after which you can put away your soldering iron.

Now to remove the liner from the acrylic housing pieces and put it all together. Be very careful not to over-tighten the bolts otherwise you will shatter the housing pieces and be cranky. If all is well, you’re finished clock will appear as such:

The clock in use:

And finally, our ubiquitous video demonstration:

VFDs can lose their brightness over the years, and can be difficult to replace – so if you want many, many years of retro-time it would be smart to buy an extra tube from adafruit with your kit, or a modified DeLorean.

Overall, this was an interesting and satisfying kit to assemble. Not for the beginner, but if you have built a few easier kits such as  the “TV-B-Gone” with success, the Ice Tube clock will be within your reach. Furthermore, due to the clear housing, this kit is a good demonstration of your soldering and assembly skills

You can purchase the kit directly from adafruit industries. As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts. Or join our Google Group.

High resolution images are available on flickr.

[Note - The kit was purchased by myself personally and reviewed without notifying the manufacturer or retailer]

Otherwise, have fun, be good to each other – and make something!