Pic Microcontroller Tutorial Pdf

[Tisham Candella]

Thisis my first of five posts in this microcontroller tutorial series. Throughout this tutorial, I will be building a microcontroller circuit while documenting the process. By following what I do, you can make your own at home.

My goal is to make a circuit that is as simple as possible, and which requires no external programmers or debuggers. You should be able to just plug it into a USB port on your computer and program it.

Now, all you have to do is to make a program that reads from the infrared sensor and controls the motor. In your code, you can make sure the robot stops if it sees something in front of it, and make it turn to either left or right before continuing.

When you know how to build microcontroller circuits, there are almost no limits to what you can do! And by following this microcontroller tutorial, you will learn to use microcontrollers in your own projects =)

In your program, you will be able to make decisions based on the input. So you can make a program that will start to blink a light if the temperature goes above or under a certain level. Put this into your beer-brewing room and you will get a visual alarm if the temperature for brewing is not right.

Throughout the tutorial, I will show you the steps you need to take to build your very own microcontroller circuit. You will then be able to use this circuit to build a blinking lamp, a robot, or some other idea of your own.

Welcome to this Introduction to Microcontroller Programming tutorial series. If you are looking to learn the basics of embedded programming for microcontrollers (and a bit of embedded hardware design as well), I hope these tutorials will help you along that journey. These are my first postings here, and I am writing this tutorial series because over the years I have seen countless newbies asking the same questions and tripping over the same stumbling blocks, and I thought I might be able to come up with something useful in answering those questions, and in avoiding those tripping points.

Every rule has one many exceptions. This applies to just about everything you will read in this tutorial. If you read "X" here, don't think it means "X and only X, in every possible situation, with no exceptions or qualifications, now and forever." Microcontroller designers have come up with many different, interesting and sometimes just wierd ways of doing things. And as an microcontroller user and programmer you too can come up with many different and interesting ways of doing things too. In my experience, given an N-step program, there are probably at least N-squared ways of writing that program. The goal of this tutorial is to try and give you a solid foundation for μC programming, not to be a comprehensive encyclopedia of the field. For every example program, I will try and write it in a simple and understandable fashion and let you discover your own clever tricks further down the road.

Another possible source of confusion is in terminology. Different manufacturers quite often use different terminology for the same or similar features, registers and configuration/status options. In this tutorial sometimes I will adopt the terminology used by one of the μC families used in the tutorial, and other times I will use non-specific terminology. I will use whatever seems to be suitable for each situation.

Embedded programming is the term for the computer programming that lives in and operates the great many computer-controlled devices that surround us in our homes, cars, workplaces and communities. To be clear, all microcontroller programming is embedded programming, but not all embedded programming is microcontroller programming. A little more will be said about this further along. Sometimes the terms will be used interchangeably, but the focus of this tutorial series is always on microcontrollers.

Another difference from general purpose computers is that most (but not all) embedded systems are quite limited as compared to the former. The microcomputers used in embedded systems may have program memory sizes of a few thousand to a few hundred thousand bytes rather than the gigabytes in the desktop machine, and will typically have even less data (RAM) memory than program memory. Further, the CPU will often be smaller 8 and 16 bit devices as opposed to the 32 bit and larger devices found in a desktop (although small 32-bit microcontrollers are now under a dollar in moderate quantities, which is amazingly amazing). A smaller CPU word size means, among other things, that a program will require more instructions (and thus more clock cycles) than an equivalent program running on a CPU with a larger word size. And finally, the speed at which smaller microcontrollers run is much less than the speed at which a PC runs. Typical smaller microcontroller clock rates are between 1 and 200 MHz, not the GHz rates of PCs.

A microprocessor is usually understood to be a single-chip central processing unit (CPU), with the CPU being the "brains" of a computer - the part of the computer that executes program instructions. A microcomputer is any computer built around a microprocessor, along with program and data memory, and I/O devices and other peripherals as needed. A microcontroller (often shortened to μC in this tutorial) is a single chip device which has built onto the chip not only a microprocessor but also on the same chip, nonvolatile program (ROM) and volatile data (RAM) memory, along with useful peripherals such as general-purpose I/O (GPIO), timers and serial communications channels. Thus it follows that all microcontrollers are microcomputers, but not all microcomputers use microcontrollers.

In smaller embedded systems it is most common to use microcontrollers rather than microprocessor-based designs since microcontrollers give the most compact design and the lowest hardware cost. Larger embedded systems, on the other hand, may use one or more microprocessors if a microcontroller of suitable speed and functionality cannot be found. This can extend to the use of industrial PCs and even more powerful hardware. It is also possible to include both microprocessors and microcontrollers in a complex embedded system. The only real rules are, use whatever device(s) fit the task, given the constraints on budget, availability, time, tools, etc.

It should also be pointed out that with most microcontrollers it is possible to add external memory and peripherals, should the on-board mix not take care of all the system needs. When it makes sense to add such external devices, as opposed to choosing a larger microcontroller with the needed resources on-board, is a choice that needs to be made on an individual design basis.

There is some discussion about what it means to call a device an N-bit processor, but it's fairly obvious in most cases. If the device can perform most of its data manipulation instructions on data words up to N bits in size, the device is an N-bit processor. By way of example, a device may have a full set of instructions that can operate on 8 bit data, along with a few instructions that operate on 16 bit data. That device should be considered an 8-bit design, even if the marketing department says otherwise and calls it a 16-bit chip.

To give a bit of an overview of the different flavors of microcontrollers available, this tutorial will be written around one 8-bit family (the Atmel AVR) and one 32-bit family (the ARM Cortex M3 architecture in the form of the STM32 family). These two families were chosen to give a fairly broad picture of the devices and approaches found in the world of microcontrollers. The first few software examples will be written in assembly language for each of these families, as well as in C. After that, examples will only be written in C.

While you could, I suppose, work through much of this tutorial using just a microcontroller simulator, I strongly recommend that you have either a microcontroller training/development board, or even just a bare μC chip, assorted components and a powered breadboard. In addition you will need a C compiler that targets your device, and optionally an assembler for your device. You should have no trouble finding a free assembler for your chip, and you should also be able to find a free C compiler, even if it is a reduced-functionality version of a commercial compiler. You will also need a method of downloading your programs into your μC. The details of this download process will depend intimately on the particular μC and board it is mounted on.

As far as test equipment goes, digital multimeters are really cheap, and there's no excuse not to have one. Places like Harbor Freight sometimes have them on sale for a few dollars. The other piece of equipment that any embedded engineer must have is a decent oscilloscope. Don't panic, a scope is not required for these tutorials. However, if you can get ahold of one, you will learn more and save yourself a fair amount of time in the bargain. USB scopes give good bang for the buck, as do some import scopes (or, of course, a working used scope). At the end of last year I treated myself to a beautiful Agilent scope with a huge (to me) screen, and every time I use it I'm glad I spent the money.

This is a good time to talk a bit about the various programming languages that one can use to write embedded software. The two languages I will use in this tutorial are C and assembly language. The first thing I want to point out is that these are not the only two languages available to embedded programmers, and that in many cases other languages may be a better choice. That being said, both C and assembly language are useful not only for learning about μC programming, but also for actually doing productive μC programming. They are also ubiquitous in that no matter what microcontroller you choose, it will almost certainly have available both an assembler (for processing assembly language source code) and a C compiler (for processing C source code). The same is definitely not the case for other languages. But I would encourage you to consider other languages if you are so inclined and, big IF, if they are available for your device family.

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