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by Tim Blythman So you’ve built a mammoth version of our LED Christmas Tree project from last month (or at least you’re thinking seriously about doing so!). It’s huge and has hundreds of LEDs. You want to make the tree do more than twinkle; you want it to really attract attention! Here is how you can make the most of the hardware, with some clever software to control it. Y ou would have seen our incredible stackable Christmas Tree project last month. It cleverly combines many small, low-cost boards with eight LEDs each to form an illuminated tree of just about any size. If you’re enthusiastic, it could easily turn into the biggest SILICON CHIP project you’ve built, so we’ve created a program and some more sample Arduino code to help you achieve that and get the best out of it. The software presented here allows you to experiment with your tree layout without having to do any soldering at all. It will show you what your tree will look like (up to a maximum of ninety-nine boards), and also tell you the order in which their shift registers are addressed. This program also allows you to generate Arduino code (which is of course C/ C++ compatible) to create patterns based on the phys38 Silicon Chip ical and logical locations of the LED boards and individual LEDs within the overall tree. This means you can generate patterns such as light radiating up the tree from the base, moving side-to-side, star bursts or various other geometric patterns. But wait, there’s more! No, you don’t get a free set of steak knives. But the software presented here can also interface to the Christmas LED Tree via the Digital Interface Module and send it commands to control an attached tree. You can click on individual LEDs and watch them turn off and on in real time. You can also use it to generate the commands for a given illumination pattern, allowing it to be delivered to the Tree later, using separate software (eg, Arduino or BASIC code). And in case you haven’t built the Digital Interface Module but have a spare Arduino board lying around, we’ll present some Arduino code to allow you to emulate some of its basic features, so you can use that Arduino to drive your tree with these more advanced patterns. LED Tree Data Map Program This application is written Australia’s electronics magazine siliconchip.com.au in the Processing language, which also happens to be the origin of the Arduino programming language. If you haven’t heard of it before, see the panel at right for more information. The general idea behind the LED Tree Data Map Program is that the graphical interface gives you a virtual view of your Tree. You build it by adding tree boards on top of existing boards, by clicking on the branch location where you want to add them. This is useful both for experimenting to see what size and shape you want to make your tree but also, once you have built it, you can create an identical tree in the software, which then produces the data you need to drive its LEDs in various patterns. Installing the software We’ve created pre-compiled Windows and Linux versions of the LED Tree Data Map Program. The Linux version has been complied for three platforms: x86 (32-bit), x64 (64-bit) and Raspberry Pi. All four versions are available for download from the SILICON CHIP website. There is no installation as such; you just need to extract the relevant executable from the ZIP archive to a folder on your computer and then run it. But since Processing is based on Java, you need to have the Java Runtime Environment installed on your PC to run the compiled programs. The easiest way to ensure that you have an appropriate version of Java installed is to download and install Processing. You can get it from: https://processing.org/download We haven’t provided a compiled Mac version of the software since we don’t have the hardware to do so. But if you have a Mac, you can use the Processing software to compile the supplied source code. You can also use the Processing software to make changes to our software and re-compile it if necessary. We used Processing version 3.37 to create and test the program. What is “Processing”? The clever little program we have put together as part of this article has been written in a language called Processing. You may not have heard of it, so let us explain. . . Processing is a programming language which is designed to allow people to easily create visual content. It is an opensource, cross-platform project, meaning that anyone can get a copy of the source code and it’s designed to run on a variety of different operating systems. It can even run on the Raspberry Pi and some other single board computers. If you want to create an app for your phone or tablet, there’s even an Androidcompatible mode, although we haven’t tried it ourselves. We have never really needed to use its particular features before. But in this case, being able to create a graphically interactive and intuitive program was the deciding factor. The Processing website at https:// processing.org/ says that it is designed “for learning how to code within the context of the visual arts”. While that might seem a poor fit for an electronics magazine, it happens to suit us very well since it means that we can easily depict and manipulate the physical layout of hardware on-screen. By the way, the language used in the Arduino IDE is called Wiring and is built on the Processing language. If you are familiar with Arduino programming, you will find that the Processing IDE (Integrated Development Environment) is nearly identical to the Arduino IDE, apart from the colour scheme. So it seems Processing has a similar role in teaching graphical programming as the Arduino does for teaching embedded programming. Processing is written in Java and when it compiles projects into stand-alone executables, they run on the Java platform as well. This was another reason we chose processing. While the majority of our readers run Windows, we don’t want to exclude those who have a Mac or run Linux. And since we could create a stand-alone version of our program, you don’t need to install the IDE to use it. The language used is Java, which is similar to C/C++, so programmers familiar with those languages (or the many similar procedural languages which have been inspired by them) should have no trouble adapting. There are some some small differences; for example, the #define and #include “preprocessor directives” are not used, but you can import Java libraries, which we have had to do to add clipboard functionality to our program. Building a tree When you first open the program, a single LED Christmas Tree board appears at the bottom of the window. When you move the mouse cursor to a location where clicking will lead to an action, a circle is shown. A large siliconchip.com.au The Processing IDE looks very similar to the Arduino IDE. You can even see some of the language similarities, eg, the ‘setup()’ function. Australia’s electronics magazine December 2018  39 Fig.1 (left): when the software is launched, a single “root’ board is present. Simply left-click on the location where you want to add another board and it will appear. Right-click to remove it. The white dots also indicate which LEDs have been toggled on by clicking. Fig.2 (right) : here’s a representation of the 38-board version from last month’s front cover. It only takes a minute or two to set it up. One useful aspect of this software is you can see whether any boards would overlap in your design – and you can even test a tree up to 99 boards in size to see how it would look. green circle appears in places where you can add another branch to the tree (see Fig.1). As the tree gets bigger, you can use the “=” (+) and “-” keys on your keyboard to zoom in and out and the arrow keys to resize the window. The program automatically assigns a number to each PCB, which is displayed on top of that board. This indicates what order the boards receive data as it passes through the shift registers on each board. This assumes of course that any unconnected ends have their DO and DI pins bridged, as explained in the article last month. You can remove branches (one at a time) in reverse order by right-clicking instead of left-clicking. This allows you to “backtrack” which is handy if you make a mistake but also useful if you are experimenting to see which of various different tree configurations is best. The program assumes that the boards are simply butted against each other rather than being spaced slightly as if they were fitted with headers. But given that you can plan with precision how the tree will look using this software, it is well-suited to creating a permanent arrangement, with the boards joined by short lengths of stiff wire. Fig.2 shows the large tree in the introduction of last month’s constructional article re-created in the LED Tree Data Map program. Driving the Tree directly If you’ve built the Digital Interface Module and have some LED Christmas Tree boards connected to it, you can control this combination directly from the LED Tree Data Map Program. Press the “,” (<) and “.” (>) keys on your keyboard to scroll through the displayed serial ports until the port corresponding to the LED Tree Control Board appears, then press the “s” 40 Silicon Chip key to connect to it. The port name turns green if connection is successful. Assuming the physical layout matches the layout you have created in the program, clicking on one LED on the screen will cause it to toggle on and off, both on-screen and on the actual board. Of course, if the two layouts are different, anything could happen! A handy feature is that you can press the “t” key to copy the current state of the LEDs to the clipboard, from which it can be pasted into a text editor for manipulating. This data is in the form of hexadecimal digits preceded by a “v” and followed by a “V” to match the 9600 baud HEX SPI format of the LED Tree Control Board. A simple way to use this data is to paste it into a serial console program (such as TeraTerm, PuTTY or even the Arduino Serial Monitor), which will then send it on to the Digital Interface Module and on to the Tree. You could save a number of these Tree states to a text file in order and send them to a serial port using an- other program, or even the following command from a Windows command prompt (assuming your file is called “test.txt”): copy test.txt \\.\COM30: Making a map of the Tree The software does not have any functions to save an image of the tree you have created but you can use your operating system’s screen capture function to make a copy of the map once you have settled on a layout. In Windows, you can do this by pressing ALT+PrintScreen and then loading MS Paint (or another image editing program) and pressing CTRL+V. You can then save the resulting image to a file. This is a good idea, so that you will remember exactly where to wire the boards when you are building the tree (if you haven’t already). Pressing the “c” key on the keyboard copies the current layout information to the clipboard, in the form of Arduino code. We’ll now explain how that can be used. Controlling the Tree with an Arduino In the constructional article last month, we explained how to use a basic Arduino sketch to make the LEDs in the tree twinkle. But with the code created using the “c” key, you can do much more. Once it’s in the clipboard, the generated code can be pasted directly into a blank Arduino sketch created in the free Arduino Integrated Development Environment (IDE). If you haven’t used the Arduino IDE, you will need to download it from the #define LED_BOARD_COUNT 4 int led_board_rotation[LED_BOARD_COUNT]={0,-1,0,1}; int led_board_depth[LED_BOARD_COUNT]={0,1,1,1}; int led_board_x_coord[LED_BOARD_COUNT]={320,262,320,378}; int led_board_y_coord[LED_BOARD_COUNT]={639,516,490,516}; #define LED_PIXEL_COUNT 32 int led_pixel_x_coord[LED_PIXEL_COUNT]={ 331,333,341,348,320,285,300,309,256,234,222,203,173,154,196,234, 331,333,341,348,320,285,300,309,399,424,448,476,465,436,416,390 }; int led_pixel_y_coord[LED_PIXEL_COUNT]={ 619,586,561,527,514,521,565,610,495,470,446,418,429,458,478,504, 470,437,412,378,365,372,416,461,510,488,476,457,427,408,450,488 }; Fig.3: sample data generated from a four-board tree. This includes information about the position of each board and LED in the tree, which the Arduino (or other) software can then use to calculate which LEDs should turn on when, to give particular patterns of light. Australia’s electronics magazine siliconchip.com.au Fig.4: the design for the small nine-board tree, used to demonstrate some of the patterns that our code is capable of generating. The program reports the board numbers in logical shift register order, as well as how many LEDs and boards are needed for construction. following link: www.arduino.cc/en/main/software This program is used to write “sketches”, as Arduino programs are known, as well as upload them to an Arduino board. The web page at www.arduino.cc/en/Guide/HomePage explains the basic workings of the IDE and Arduino-compatible boards. For the examples below, you just need to load the sketch file, select the correct board type and port from the “Tools” menu and then click the “Upload” button to test the sketch. We’ve created a few sample sketches to show how to use the data from the LED Tree Data Map Program. Fig.5 shows the wiring required to connect the Arduino board to your Tree. We used an Uno clone for our tests but these sketches should work on just about any Arduino-compatible board. The connections are as follows:    Arduino 5V GND D2 D3 D4 D5 ARDUINO UNO ‘Root’ Tree board 5V GND DI DO LT CK Fig.3 shows the data generated for a simple case of four boards, with one sub-board connected to each of the three branch connections on the root board. The first line, starting with #define, simply tells the program how many boards are in use. This value is also used to dimension the following arrays which contain information about the location of each board. The second line defines the “led_board_rotation” array which contains an integer value for each board indicating the orientation of the board. A value of zero means the board is parallel to the root board, while negative values indicate anti-clockwise rotation and positive values indicate clockwise rotation, in multiples of 45°. So +1 = 45° clockwise, +2 = 90° clockwise, -1 = 45° anti-clockwise, etc. The third line defines the “led_board_depth” array which indicates how far each board is from the root board. The root board depth is zero, the boards connected directly to the root board have depth one and so forth. This is a handy approximation to the vertical position of each board. The fourth and fifth lines define arrays named “led_ board_x_coord” and “led_board_y_coord” which give the cartesian coordinates of the bottom middle of each board. The root board is always at 320,639 with the values ranging from zero up to 639. Increased x values indicate boards which are further to the right while decreased y values indicate boards which are further up. While these values could potentially be useful in some cases, most patterns would use the individual LED coordinates which are what is provided by the remainder of the code. The second #define indicates how many total LEDs there are in the tree (which is always eight times the number of boards) and the final two arrays contain this many integers. Those integers are the cartesian coordinates of each LED, in order from first to last in the shift chain, using the same coordinate system as described above for the boards. Using some simple calculations, you can create some amazing patterns by checking the coordinate of each LED and determining whether or not to turn it on, based on various geometric patterns. Example sketches We have provided five sample sketches, to show off some of the patterns that it’s possible to generate once you have the data for your Tree. These are just the starting point; you could use them as-is or you could expand on them, to CHRISTMAS TREE make even more interesting and spectacular patPCB terns. You could even combine them into a single 5V sketch which can cycle through several different PIN patterns over time. GND Our first example sketch is named “9_Board_Tree_ PIN D1 rotate_scan.ino” and it illuminates each group of D0 PINS LEDs in a tree depending on their rotation. CK 2-5 LT Although this won’t strictly give a left to right motion if your tree has loops or reverse curves, it still provides an interesting display. While as the name suggests, it contains the data to Fig.5: this shows how you can drive the LED Christmas Tree suit a Tree made from nine separate boards (as shown from an Arduino. While we gave a simple test sketch at the time, this month we’re also providing a general-purpose interface sketch in Fig.4), it is not limited to being used in this way. You can use it with a Tree made from any number which allows this configuration to work with our new software. 42 Silicon Chip Australia’s electronics magazine siliconchip.com.au of boards in any configuration. You simply need to replace the coordinate definitions at the top of the file with those generated from your Tree design, using the method described above. Nine boards were chosen simply because we felt that four boards were not enough to really show off the features of this software. You can change the data to suit your tree, of any size, in each of the five examples provided. The code will adjust to suit your Tree, as it determines the minimum and maximum values at runtime in the setup() function. The second example sketches is called “9_Board_Tree_depth_scan.ino” and it first illuminates all the LEDs on the root board, then on all the boards with depth = 1, then depth = 2 etc. This gives the effect of light shooting up and out the tree branches. Its code is virtually identical to the first example, with just one line changed. The third and fourth examples are called “9_Board_ Tree_x_scan.ino” and “9_Board_Tree_y_scan.ino”. These work similarly; the former causes LEDs in the tree to light up from left-to-right, then right-to-left, creating a vertical line of light which moves across the tree and it repeats forever. Similarly, the latter causes a horizontal line of LEDs to light up from bottom-to-top and then top-to-bottom. The final example is the most complex and this is “9_ Board_Tree_starburst.ino”, which causes the LEDs in the middle of the tree to light initially, and then the light spreads outwards in growing circles. Saving memory If you have a large tree, you may run out of RAM to store the resulting large data arrays. In that case, you would need to add “const PROGMEM” to the start of each line defining an array. That will cause them to be stored in flash rather than RAM. But note that you will also need to make changes to the way that the program accesses the data; but we won’t go into detail on that aspect here. If you want to see some examples of how to access PROGMEM variables, refer to: www.arduino.cc/reference/en/language/variables/utilities/progmem General purpose Arduino control board Finally, we’re providing an extra Arduino sketch which provides an interface between the LED Tree Data Map Program and an LED Christmas Tree, even if you haven’t built the Digital/SPI Interface Module described last month. You just need an Arduino board and some jumper wires. siliconchip.com.au It only works with the 9600 baud HEX SPI mode described last month for the Digital Interface Module, as there isn’t an easy way for most Arduino boards to detect the baud rate their hosts are using. But that’s certainly good enough to do some testing or maybe even drive a Tree in a Christmas display. Connect the tree to the Arduino using the same wiring as the previous example (Fig.5) and load the sketch, which is called “Arduino_HEXmode_ Tree_emulator.ino”. Like the other sketches provided, it should Fig.6: this work on most Arduidemonstrates no boards. that you don’t The procedure for need to be selecting the serial celebrating Christmas to build this project – port in the software you can turn it into a is the same as described above; use the Hanukkah menorah “,” (<) and “.” (>) keys instead! to change the serial [See https://en.wikipedia. org/wiki/Menorah_(Hanukkah) port, then press “s” for an explanation of why it has to connect. SC nine branches.] MUSICAL CHRISTMAS STAR DIY PROJECT FROM PICOKIT SC Create some holiday cheer with a DIY Musical Christmas Star project from PicoKit. This soldering kit has movement sensing to light some colourful LEDs and play some Christmas carols. Optionally, you can upload your own songs with the PicoCODER programming cable from PicoKit (just $15 extra if bought together with the PicoSTAR). The PicoSTAR kit is supplied with a pre-programmed PIC12F510 from Microchip Technology and is compatible with PicoKit’s own ALPHA Code programming software and coding with C and ASM languages through the MPLAB-X software from Microchip Technology. PicoKit - Maker Space Solutions for al OffeHrIP SpeciIC C SIL OdNers* ea $ 17 R $ 22 P P& GST & PLUS bsite *see we ils for deta Australia’s electronics magazine Upper Caboolture 4510, QLD Phone: 07 5330 3095 www.picokit.com.au December 2018  43