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PIC FUN AND Way back in time, last century even, we presented a neat little PIC-based project called LED FUN. Here’s its big brother, another PIC project called PICFun2. And while it can flash LEDs, it is capable of doing a whole lot more! A ctually, the project we referred today that an understanding of them is programmed (or “written to”) only to above wasn’t all that long almost essential for anyone interested once. Their program cannot be erased ago – February 1999 to be pre- in furthering their electronics knowl- – to change the program, you have cise (it just seems long ago!). LED FUN edge, whether that be at a hobby, stu- to change the chip. These are much was based on a PIC12C508 which was dent, technician or professional level. cheaper to produce than the re-programmable type and are used when programmed to flash LEDs in a variety When we say common, we mean all of the code has been tested or “deof patterns. it. Unless you’ve just woken up, The board was designed and prothe chances are that already today bugged”, ready for a production run. duced in Australia by Labtronics. Now you’ve used not just one, but several If you want to know more about reincarnated as eLabtronics, the new devices containing PICs or other mi- PICs and microcontrollers, there is a project, PICFun2, is based on a more crocon-trollers. In fact, if you woke up lot more in the PICFun manual on the powerful PIC, the 16F84. to an electronic alarm clock or clock CD-ROM – a lot more! PICFun2 has more than one What you get aim. In its “bare bones” form, it’s basically just a PIC on a PC board In the PICFun2 kit, there is with a sprinkling of components a small PC board, the PIC chip to enable you to connect it to the (16F84) with an 18-pin IC socket, outside world (or, more correctly, a buzzer, a 9-pin male D socket, the inside world – the inside of a couple of PC board mounting your personal computer!). terminal blocks, a battery holder It’s designed as an educational (no batteries!), a slide switch and aid, something for (especially) a pushbutton switch, some reschool students (or anyone else) sistors, capacitors, diodes, LEDs to “cut their teeth” on in the world and a transistor, along with some of microcontrollers. Indeed, the hookup wire. man-ual supplied (on an accomOn an accompanying CD, there panying CD-ROM) goes into a great is a range of software, manuals – deal of explanation into just what even a technical manual on the a microcontroller is and what it PIC16F8X range – and various does, long before you get to touch a other information. This CD-ROM soldering iron! There’s even a trial When they say PICFun is child’s play, they is PC (ie, IBM) compatible. version of some software to help mean it! Here is 8-year-old Emilio who built a Putting it together you program – but more on this PICFun2 kit – and it worked first time! (This version actually has a bit more on it than the shortly. The first thing to do is completeBut it’s much more than this. basic PICFUN2 described here.) ly ignore the PC board component The project software provided on layout in the instruction manual. the CD-ROM shows just a couple It will confuse the heck out of you radio, it probably contained one! of things you can do with PICs. Once for two reasons: (a) it’s an earlier PC There are many different types of board (new ones are different!) and you’ve learned how to drive them, you’re ready to start writing your own PICs (and other microcontrollers). (b) it shows a different project to what Some, such as the type we are us- you’re building here. Use the PC board code to do, well, whatever you want ing here, can be programmed and component layout we’ve shown here to. erased hundreds, often thousands of and the accompanying photo. Why would you want to learn about times. Others, such as the ones used microcontrollers, and PICs in particuStep-by-step instructions are givin commercial equipment, can be lar? Well, they’re in such common use en in the manual but assembly is 78  Silicon Chip www.siliconchip.com.au GAMES basically the same as any other kit: start with the lowest profile components first – the resistors, followed by the diodes, capacitors, transistors and LEDs. The hardware (IC socket, switches, D9 socket, terminal blocks and buzzer) is the last to be soldered in place. Soldering the D9 socket in place is probably the most tricky bit. The easiest way to do it is to undo the nuts on each end which hold the plug shell in place (remember which way up it goes!), soldering the pins to the PC board and then replacing the shell and the nuts. Also the on-board terminals need a bit of explaining: you slide these By Ross Tester In its most basic form, there isn’t much to PICFun2 – apart from the PIC chip itself there is just an input from your PC (the D9 connector), power supply and some output LEDs. But this is only the starting point. PICFun2 can be expanded to do a lot more than flash LEDs! Use this overlay to populate the PC board, not the one in the manual. The circuit diagram is overleaf. www.siliconchip.com.au December 2001  79 In its simplest form, PICFun2 contains only the PIC chip itself, some power supply components, the interface to your PC and some output LEDs. The manual has a number of programming suggestions. together to form a four-way terminal block before soldering them in place. The “open” side of the plug (ie, the bit where you poke in the wires!) has to face to the outside edge of the PC board. And lastly, the LEDs: the manual makes some comment about aligning all the LEDs so that their longer leg (the so-called “negative lead” – we’d call it the cathode!) goes “via the thick track to the negative rail”. What they should simply say (we think!) is that all the LEDs should be soldered in so that their flat sides are facing the top of the board as you read the labels. Now that’s a tad simpler, isn’t it? And yes, there are a couple of LED positions not used. What you should end up with is a PC board similar to that photographed on page79. As you can see, there is not a lot of the PC board “populated”; that is for later expansion when you start doing really clever stuff with the PIC. Testing the board Having assembled the hardware for the controller the next step is to test it. 80  Silicon Chip First of all, you need to supply power. The manual talks about 3 x “AA” cells but a 4 x“AA” cell holder is supplied. Use four cells, otherwise you will have an open-circuit power supply! The 5.1V zener diode included in the circuit will regulate the voltage to within the PIC’s specs. Install the software provided with the PICFun2 kit. Start the program Picplc. This program is used to send code in binary format to the 16F84 for programming. Code for this is obtained from the appropriate *.hex file. When started you will be asked for the location of the hex file you wish to download. Load the file and the number of the serial port being used for programming (ie; c:/PICFUN/mode1. hex 2 where 2 is the com port and the file is located in the c:/PICFUN directory). Leave a space between the x and the number. It is suggested that you use the mode1.hex file for the test. This is found amongst others on the disk provided. Follow the steps below. They will lead you through the processes re- quired to program the chip as well as providing a test for its successful construction. Step 1 Connect a 9-pin serial cable (not supplied with the single version of the educational kit) from the D9 port connector on the microcontroller to an available serial COM port on your computer. You will need to know if it is COM 1 or 2 that you have selected. Check the gender of the connectors on your cable. A gender changer may be required. (The cable is a 1-1 wired serial cable female to female, 9 pin to 9-pin or 9-pin to 25-pin). Step 2 Run START on the supplied CD. Install all the software ( PICFun and MPLAB ) and drivers to drive C:/ PICFUN of your computer. You will need approximately 5Mb of hard disk space. Step 3 With the computer off, connect the PICFun2 to the serial connection on your computer, then start the computer. Keep the serial lead and programmer connected during start up and the www.siliconchip.com.au Parts List – PICFun2 1 PC board, 80 x 48 mm, coded PICFun2 2 PC board mounting terminal blocks 1 18-pin IC socket 1 piezo buzzer 1 miniature pushbutton switch, NO contacts 1 SPST miniature slide switch, PC board mounting 1 4xAA battery holder 4 AA batteries (not included in kit) 1 9-pin “D” serial interface connector, right-angle PC mounting 1 “straight through” serial cable, 9-pin female to 9-pin female Hookup wire Semiconductors 1 PIC 16F84 microcontroller IC (IC1) 1 BC547 NPN transistor (TR1) 4 1N914 silicon signal diodes (D2-D5) 1 5.1V 400mW zener diode (D1) 6 red LEDs (DOL1-6) Capacitors 1 100µF 25VW PC electrolytic 1 0.1µF ceramic (code 104 or 0.1) 1 22pF ceramic (code 22p or 22) Resistors (0.25W, 5%) 7 10kΩ 1 4.7kΩ 8 390Ω 1 10Ω slide switch on the PICFun PC board towards the middle of the unit. Step 4 The slide switch is vital to the programming and running modes. It tells the PIC whether it is in a write (programming) or read mode. Make sure it is connected (towards middle) during programming. When running programs it must be disconnected (towards outside). Power is not applied to the PICFun2 during the programming process. The required voltage is derived from the serial interface. Power is only applied during the running process. Step 5 Go to the Start/Programs list and run the Picplc programmer software. (NB: In the PICFun2 software setup and supplied files the term ‘PIC PLC’ is used to describe the device as it was www.siliconchip.com.au originally known by that name.) Step 6 Under Windows you open the the program in the normal manner. You’ll need to tell PICFun2 which COM port you are using. The software will then transfer the sample program “model. hex” to your PICFun board. Step 7 Test your PICFun2 programmer and micro controller. Disconnect the serial lead and jumper. Insert batteries into the holder (4 x 1.5V cells). Once power is applied the program will start to run. When the switch is pressed for a second and then released, the LEDs should light up randomly and a sound sequence be produced by the piezo buzzer. Kits without compromise What if it doesn’t work? OK, we’ll be honest. Ours didn’t work first time! Here are just a couple of the traps you could fall in to. (1) Check your soldering and component placement. 99% of all faults with kits are found in this area. Are all the diodes and other polarised components around the right way? Have you managed to solder a bridge between adjacent pads? Have you forgotten to solder a component in (or, have you made a “dry joint”)? Having exhausted all those possibilities through careful inspection and checking, let’s move on to the other 1% (our problems were in the 1% category!). (2) Is your power supply/plugpack connected the right way around? The series diode will prevent anything catastrophic happening if you connect the power back-to-front . . . but it won’t work, of course! (3) Is your 9-pin D to 9-pin D cable a true serial cable? Many of the cables have pins swapped in them (so-called “null modem” cables) and these will not work. If in doubt, check for continuity between pins with your multimeter and some short lengths of wire poked into the socket holes. Pin 1 must connect to pin 1, 2 to 2 and so on right through to pin 9. (Not all pins are used but the cable should be wired through). Similarly, you must use a female-to-female cable. If you have a female- to-male cable with a gender changer on one end, there may be a crossover in that gender changer or cable. (4) Have you followed the software loading/downloading steps carefully and have you properly initialized the software? “Sound quality to die for” Rolling Stone Magazine “..A new benchmark in every criteria” Best Buys Home Theatre Speaker Kits without compromise from $312 pr to $8,863 pr FreeCall 1800 818882 www.vaf.com.au vaf<at>vaf.com.au December 2001  81 RESISTOR COLOUR CODES    No.  7  1  8  1 Value 10kΩ 4.7kΩ 390Ω 10Ω 4-Band Code (1%) brown black orange brown yellow purple red brown orange white brown brown brown black black brown (5) Is the path to the hex file correct? (6) Have you connected the correct COM port? (7) Have you set the programming switch/jumper on the board before running the program (ie; applying power). Where to from here? Space does not permit detailing all the applications possible with the simple PICFun2 board – you’ll find a lot more on this in the manual and on the CD-ROM. One of the sample programs on the CD-ROM is a demonstration temperature controller, which uses the PIC to sense the temperature of a thermistor. The thermistor, in turn, is under the influence of both a small light globe (heater) and a fan (cooler), each of which are also controlled by the PIC. This does require a few more components than what we’ve shown here, by the way. A setup screen is provided on the PC through which you can enter maximum and minimum temperatures. When you download and run the program, you’ll find the light comes on to heat the thermistor up to your maximum temperature, at which point the light goes off and the fan goes on to cool it back down to the minimum. Such a demonstration board is shown separately. Sure, it’s only a gimmick – but it’s a great little demonstration of what a microcontroller can do and makes an interesting school project. Just imagine if that light, thermistor and fan were replaced by a large heating, sensing and cooling system for a city skyscraper. Impossible? Nothing is impossible for a microcontroller! Creating a program As we said at the outset, the PICFun2 is just a starting point. Writing your own software (also known as code or a program) is not easy for a beginner – but start out simple and 82  Silicon Chip 5-Band Code (1%) brown black black red brown yellow purple black brown brown orange white black black brown brown black black gold brown keep practicing – and pretty soon you could be an expert! Microchip Technologies, the makers of PICs, have provided a number of shareware software tools for the support of their products. “MPLAB”, which is downloadable from their web site (www.microchip.com) offers a text editor, an assembler and software simulator for the writing, assembling and testing of programs. The text editor is used to compile the source code. This is made up of device instructions, data, directives and comments. The program is written in mnemonic form and is based on an instruction set peculiar to the PIC device. Programs consist of a series of instructions that detail consecutively the processes the programmer requires the microcontroller to execute. Programs are set out in a special format so that labels, instructions, directives and comments are recognised by the assembler. The assembler takes the compiled source code and processes this to produce an assembled (*.asm) file and an output (*.hex) file. The compiled source code is saved as an *.asm file while the *.hex file contains the data ready for downloading to the microcontroller. The hex file must be loaded into a program such as Picplc to convert it into binary form first. Debugging It’s a pretty rare programmer who manages to write code without errors, or bugs. Getting rid of these is not called squashing or swatting, it’s called debugging. MPLAB contains a software simulator which enables programs to be checked and debugged. The simulator enables programs to be observed step by step and shows what is happening in the various register and memory locations. Simulators can be invaluable tools for program development but have their limitations since they are not the real device. For the simulator to work, a hex file must be loaded into it. In this section we have set out some of the basics for preparing a program. We have included examples of how all three tools are used in the process. Your first step will be to install the MPLAB software if this has not already been done. About 8Mb of hard disk space will be needed. The zipped files can be saved to individual disks and installed after downloading. And if you want more information, the web contains thousands – no, probably millions – of pages of data, programs and help on PICs as well as other microcontrollers. If you don’t believe us, go to www.siliconchip.com .au and type PIC into the Google search engine. See you in a couple of years! BitSet program Included in the kit is a trial version of eLabtronics' “BitSet” software, an icon-based programming tool designed to replicate all the instructions available in the 16F84 instruction set. It utilises windows and drop down menus in which all the information contained in a text instruction can be entered and implemented on variables and literals. This provides a convenient method of entering instructions and data. The names assigned to the icons are representative of the group of functions SC hidden behind each button. Where from? The PICFun2 is designed by eLabtronics, 12-20 Gilles St, Adelaide, SA 5000. Tel (08) 8231 5966 Fax (08) 8231 5266 website: www.labtron.com.au Price of the basic PICFun2 is $78.00 +GST. It is also available through Altronics stores and mail order (1800 999 007). www.siliconchip.com.au