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ADDING INFRARED TO YOUR In the December issue we had our first look at the Viper robot from Microbric – a new concept in project building that can turn a beginner into an expert in seconds! Now we’re going to start adding more functionality to the Viper by giving it some infrared control capability O ne of the difficulties new or would-be electronics enthusiasts Part 2 – by have is the (perceived?) difficulty of soldering, component identification and actual construction. While those more experienced in the art would say “just get in and learn it!” there is arguably nothing more disconcerting to a beginner than building a project and finding it doesn’t work, or work as intended, often due to a simple error that, with just a little bit more knowledge, would be easy to spot and fix. Many’s the project that has been thrown into a cupboard (or even bin!) for this reason. That was one of the stumbling blocks that Microbric wanted to avoid. And with their unique “bric” concept, they’ve succeeded very well! Soldering has been completely eliminated. If you can fasten a nut on a screw, you can build with Microbric. Component identification has been eliminated, again due to brics. Now it’s modular – some modules contain individual components, others a complete circuit element. But when you connect them together, they simply work! And the parts are reusable – you can dismantle and rebuild as many times as you like. With Microbric, you can build complex electronic devices with little or no prior electronics knowledge. You will learn as you go – that’s another one of the strong points. And that 74  Silicon Chip knowledge is not limited to electronics – other concepts will be covered along the way such as mechanics, programming and even designing your own projects. Incidentally, if you missed our Microbric introduction in December, we strongly suggest you read that before reading on. It covers the concepts and the fundamentals which are necessary background to building more complex robots (Back issues are available for $8.80 each including p&p). Ross Tester Minimum hardware requirements Before we get down to the nitty gritty, we should cover what you need in the way of a computer. Virtually anything from PII 233 up (Pentium II, 233MHz) will be fine. It would be hard to imagine one of those machines not running Windows 98, Me or XP – but that’s what is required. You’ll need a minimum 32MB of RAM (again, hard to imagine anything less) and at least 120MB of free hard disk space. As far as sound and graphics are concerned, any Windows-compatible sound card will be fine and 800 x 600SVGA with 4MB RAM will be required. As the manual comes on a CD, a CD-ROM (minimum 8x) is essential. The one area you might have problems with is an RS232C port. That’s required for data transfer to and from the Viper and regrettably, many modern computers don’t have one, using USB ports instead (here’s where older computers siliconchip.com.au will come into their own!). If your computer doesn’t have RS232C, a USB-to-RS232C converter/adaptor may be the answer (they’re cheap enough!) But note that we have NOT tried programming the Viper using this method so cannot guarantee it. The Viper kit When you open up the Viper kit (Dick Smith Electronics, K-1800, $199.00) you might think that you’ve been shortchanged because only about half the box is populated with bits. That’s deliberate – the kit contains all you need to put together the Infrared Controlled Viper with: • A motherboard (contains the microcontroller “brains” of the robot along with batteries and programming port • Two micromotor modules (each houses a high quality motor and metal gearbox plus the electronics to run them) along with two wheels; • The infrared receiver module (receives the output from the infrared remote controller, also included); • A buzzer, (plays notes and beeps; even has a volume control) • Two LED modules (with driver circuitry built in); • A button (to start and stop your program); • A switch sets the different modes of operation in your program input); • A bump sensor (detects obstacles in the robot’s path) • Plus an RS232 cable, software on CD-ROM and screw driver • And, of course, the connecting pieces to allow you to put it all together. The blank areas in the box are for supplementary or expansion kits, available separately, which you can then keep with the the main Viper kit. These includes Wheel Packs, Line Tracker modules, Sumo (robot wars) modules and even advanced projects such as the Spiderbot and Dragster. Giving the Viper Infrared Control We’re assuming that you have built the Microbric Viper (as per December 2005 issue) and have had a lot of fun playing with it. Now that fun is going to be magnified a whole lot because adding infrared control opens up whole new horizons. The infrared transmitter When you look at the hand-held infrared transmitter, you’ll probably think that it is just about the same as all of those infrareds you already have for the TV, VCR, DVD, set-top box, home theatre system, air conditioner . . . and you wouldn’t be far wrong. Most infrared remote controls work in very similar ways. They simply impress a digital code of pulses onto an infrared beam. Needless to say, because it’s infrared, you cannot see the beam. But most video cameras can, especially the cheaper ones such as webcams and security cams because, for the most part, they don’t have any filtering to “keep out” infrared. But even many stock-standard camcorders can “see” infared. If you aim the camera at someone holding the infrared remote across a room, then get them to push buttons, you’re likely to see a continuous bright white light in the viewfinder (assuming it’s working as a camera, not siliconchip.com.au a video player!). Connect to a TV set or monitor for a better view. Incidentally, this is a good way to check that the infrared remote control (for anything!) is working before you change the batteries. Many a perfectly good battery has been thrown out when it has been something else that hasn’t worked (eg, the loose nut on the keyboard . . .). It’s all in the timing The particular remote control supplied uses the 12bit Sony InfraRed Control (SIRCS) protocol – if you want to, you’ll find plenty more information about this protocol on the web (Google SIRCS). Each of the buttons on the remote control puts out a slightly different digital code. These codes are in the form of pulses which are far too fast for us to see, even when looking at them via a camera. Pressing different buttons results in very small differences between each pulse train. The receiver which we are about to fit to the Viper detects this pulse train, regardless of which button is pressed and translates it into language (actually electrical levels) the microprocessor can not only understand, but act upon and send the appropriate command. So it is actually the microprocessor which works out which button is pressed, not the receiver itself. One button might tell the microprocessor to apply power to both motors equally and move the Viper forward. Another button, for example, might be interpreted as applying power to one motor and applying reverse power to the other motor – which, fairly obviously, will turn the Viper in the direction of the wheel rotating backwards. Naturally, not all the buttons on the remote control will do anything (at least, not at the moment). Later on, as you become more adept at BASIC ATOM programming, you might be able to put some of the other buttons to use to get your Viper to do some really kinky things! But let’s get back to the task in hand: getting the Viper to work with the infrared remote. Modifying your Viper First of all, attach the Infrared Receiver module to Pin 6 on the Microbric motherboard. That’s the simplest part! In order to use the remote control with the microcontroller, you will need to follow a sequence of steps to preset the remote to work with the microcontroller. a. Put two AAA batteries into the remote control unit. b. Simultaneously hold down the S button (in the middle of the arrows) and the B button on the remote (a red light will go on in the top left hand corner of the remote. February 2006  75 c. Press the number sequence 0 1 3 on the remote buttons. d. Press the red power button on the remote. e. The remote is now configured to work with your microcontroller. Note that buttons A, C, D, E, F and G are for setting the remote control into different modes which are not required for this project. Avoid pressing these buttons as this will inadvertently set your remote into another mode. You can always return to the ‘B’ mode by pressing the B button. Entering the BASIC program Open a new file on your computer and call it IRProgram.bas You could type in the program as listed but it is fairly long and complex, so the chances are you will make a mistake. And one mistake could stop your project from working. It’s much simpler (and safer!) to load this program from the supplied CD (phew! Saves a lot of typing!). Save it (File/Save As…) to a location on you hard drive before programming it into the microcontroller. In this program you will be using the PULSIN command. This is a command that tells the microcontroller to wait for a pulse signal. You will note that it specifies the Pin for the input and then states what to do in the 0 state and the 1 state. Some things to note about the program: • This program will accept a signal from the remote control, analyse it, and then, according to the binary 16 bit number received, will either run the motor forwards, backwards, turn the LED on or play a tune. • The ‘pulse’ sequence is necessary to check all the possible incoming combinations. It is tedious to type in, but gives this program its flexibility to use multiple buttons to drive it. • Each of the buttons on your remote control has a specific 16 bit binary number (referred to as a 16 bit ‘word’). You can see four of them represented in the TESTIRDATA subroutine. The 16 bit numbers for each of the buttons on your remote control are written in the table below. You can use them to program 14 separate functions. SC Flowchart for infrared control of the Viper. When the signal is received by the infrared receiver and passed on to the microcontroller, it is looking for one of the valid codes from the table below. Remote Control Button 16 bit Button 1 button 0 0 0 0 2 button 1 0 0 0 3 button 0 1 0 0 4 button 1 1 0 0 5 button 0 0 1 0 6 button 1 0 1 0 7 button 0 1 1 0 8 button 1 1 1 0 9 button 0 0 0 1 0 button 1 0 0 1 button 1 1 0 0 button 0 1 0 0 button 0 0 0 0 button 1 0 0 0 76  Silicon Chip ‘words’ 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 siliconchip.com.au