Nuts & Volts

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■ BY CHUCK HELLEBUYCK GOING BEYOND 31 COMMANDS I ’ve had a small percentage of emails asking why I don’t teach “C” programming or assembly. I’ve had people email me details about other “better” microcontrollers or even “better” programmers than the EZPIC programmer I’ve presented earlier. The common theme though seems to be that I’m out of touch or doing a disservice because I focused on the Basic language in these articles. I’ve heard all that before, too. I’ll be the first to admit I’m no expert. I’m just trying to help beginners get started. It’s my dream that every person realizes they are capable of creating that special electronic gadget using a microcontroller. When the Personal Computer first came out people asked “What do you do with it?” Eventually, people with very little knowledge of a PC were writing programs in Basic language that launched an industry. Early killer apps such as Visicalc (the first Excel) made the Apple II computer an industry standard. Eventually programming languages evolved and so did the hardware. C, Pascal, Fortran, and other languages were soon available. If you were into programming, you were in heaven. Jobs were created that involved programming only. Companies were launched that only sold software. PICs THE LATEST IN PROGRAMMING MICROCONTROLLERS THE FEEDBACK TO MY ARTICLES TELLS ME this series on programming Microchip PICs is a success. Based on loads of email, I’ve helped many readers get back in the electronics game and comfortable programming microcontrollers. That is a reward in itself and is enough for me because many years ago, I was there, too. That success, though, also invites its detractors. 74 April 2006 GETTING STARTED WITH ■ FIGURE 1. The full version of the PICBasic Pro compiler. Microsoft — the biggest of them all — started out by offering the Basic language. A totally new profession was launched but it all started with a microchip and I never forgot this fact. Where does it say that a user who writes a program in Basic that gets programmed into a PIC and runs that custom temperature datalogger or home alarm system isn’t also a real program? If it works, who cares how you got the 1s and 0s into the chip. If, after a while, you want to move from Basic into other languages currently (and I stress currently) accepted in industry, then you have a great platform to build on. I write these articles for electronics hobbyists and also mechanical engineers, chemical scientists, basement technologists, and kids just getting started. In other words, anybody who is willing to learn can become a PIC programmer. Are there better chips out there for your application? Maybe. Are there better PIC programmers out there? Yeah, if you can afford to pay more. If my articles get you started and you eventually move to C and better chips and better tools, then all I ask is don’t forget those behind you. The help I received from those more experi- ■ FIGURE 2. The Basic Atom. enced was priceless, so I’m passing it back on to you, the reader. With all the tools, books, components, and software dedicated to Microchip PICs out there now, there is no reason to pay someone big bucks to create a prototype of that great invention in your head. Do it with a PIC. BASIC OPTIONS Speaking of tools, if you have been using the 31-command-line free sample version of the PICBasic Pro compiler, by now you probably are ready to write bigger and more complex programs or even use different PICs. The obvious next step is to purchase the full version of the PICBasic Pro compiler (Figure 1). With it, you can write programs as big as your PIC chip memory can handle. You can program eight pin PICs, such as the 12F675 or even the new 18F PICs with up to 64K of memory. All this comes at a cost though. The full compiler retails for $249.95 and even though I discount it at my website (www.elproducts.com), it’s still a lot of money to shell out if you are not sure how much you will use it. It’s like having a tool in your tool box. Once you have it, you wonder how you did jobs without it. There are other options, though.
GETTING STARTED WITH PICs BASIC ATOM One of my favorite Microchip PIC options is the Basic Atom. I’m sure you’ve seen the Atom modules in Nuts & Volts which have the same footprint and look of the BASIC Stamp modules, but what many people don’t realize is at the heart of an Atom module is actually a Microchip PIC16F876A or PIC16F877A chip with a selfprogramming bootloader inside. It’s a PIC (Figure 2) that you can purchase separately from the module and use in your PIC16F877 or 876 circuit. The story of the Basic Atom is interesting. It was created by a couple of guys in Michigan, only a few miles away from where I live. They started out by creating a PICBasic Pro compiler competitor called the MBasic compiler. It sold well, but had a lot of early bugs. Because it was only two guys, handling all the tech support became a problem. They realized that a lot of the tech support involved the differences with the various PICs. If they could focus on just a few key PICs, they felt they could make a solid compiler with the time they had. The BASIC Stamp, being so popular, became the footprint they tried to emulate, but instead of using the fetch and function BASIC Stamp method, they took their MBasic compiler and combined it with a custom bootloader program for the PIC16F876 and PIC16F877. These PIC chips have the unique ability to program their own internal memory with a small program hidden in their program memory called a bootloader. It’s kind-of like having an operating system on your PC prior to loading a program you really want to run. The features of the MBasic compiler were carried over to the Atom, so this gives the Atom access to all the PIC features, such as timers, A/D, interrupts, etc. The Atom sold well right from the start since it offered higher speed and more memory. To me, though, the big feature was the fact that I could program the Atom PIC chips and plug them into any PIC 16F876 or 877 development board. If I designed my own development ■ FIGURE 3. The in-circut debugger program screen shot. board with a serial communication circuit, similar to the RS232 circuit I used in the March issue, then I could program the Atom PIC 16F876 or 877 right in-circuit without having to remove the PIC over and over again. IN-CIRCUIT DEBUGGER (ICD) This is what locked me into the Atom. The MBasic compiler had an in-circuit debugger program (Figure 3) built in that allowed you to run your program in slow motion command by command. This made it easy to catch errors because you could see the changes in the RAM (variables), special function registers (timers, Portb, etc.), and even run sections of program in real time, but stop at a breakpoint. It was like having a Basic language driven emulator and it was included for free and in the Atom software. So, why would I be so excited about all this and why am I telling you this? It’s because they give away the Atom compiler software for free. The only catch is you have to buy the Atom PIC chips from them or an authorized reseller — like my site. The Atom chips cost $20 each, so if you are going to build a 100-piece design, then using the PICBasic Pro compiler will quickly pay for itself over the Atom, but most readers are just experimenting or building a few prototypes. For $20, you get a fullfeatured compiler with in-circuit debugger and features PICBasic Pro doesn’t have, such as floating point math and much simpler access to timers and other special function registers. Here is the best part of all. They kept most of the syntax of the Basic commands compatible with the BASIC Stamp and PICBasic Pro, so moving a program from the Stamp to PICBasic to the Atom is quite easy. I often create with the Atom using the ICD to prove out the idea and then move to PICBasic Pro for higher volume applications. The Atom has been used by so many people, it’s been proven to be a very solid compiler. I recently released my second book — this time on the Atom — titled Programming the Basic Atom Microcontroller. You should be able to find it at the Nuts & Volts bookstore, my website, and a few other resellers. My point to all this is that you still don’t have to spend more than $50 to program PICs beyond the 31 command line limit, just like my January article pointed out. I’ve even put some of my Atom-based modules on my website that are designed for the beginner that wants a complete development module with the programming interface built in. I even have my BasicBoard with LCD, LEDs, switches, speaker, and potentiometer April 2006 75
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