Three C Compilers for the PIC NOTE: This page is a little out of date now - I plan to revise it when I get a chance Writing your microcontroller firmware in a high level language is so much easier than writing in assembler. Something that might take a week to write and debug in the C language would take months if you were forced to use assembler — and, the assembler code would be buggy and hard to maintain. Unfortunately, due to the compiler unfriendly architecture of the Microchip PIC series, there are few free or low cost compilers available for the low end chips. This is where the users of the Atmel AVR series have a clear advantage, they have access to the for that chip. This article looks at three C Compilers for the PIC series of microcontrollers from the point of view of the cash strapped hobbyist and makes some recommendations as to the best way to go. Why Use a C Compiler?

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Firstly, a few words are necessary to explain why a C Compiler is such a good thing. If you are familiar with C you can skip to the next heading. Assembler gives you tight control of every CPU cycle and very efficient use of both program memory and RAM. When you write in assembler you are intimate with every detail of your code and this intimacy allows you to cut corners and craft some especially neat solutions.

This is essential when you are short of memory and must get the best speed from limited hardware. This intimacy is also the downfall of assembler when a program gets large. Anything that is much greater than 2K or 3K bytes in size starts to become a nightmare. There are so many variables to keep track of, so many side effects from calling various subroutines, and so much complexity that in many cases it is impossible to continue using assembler. Even an application for the humble 16F88 chip with its 4K of memory would benefit from being developed in C, while complex applications written for the 32 bit chips are impossible to develop for in anything other than C.

The Microchip C18 compiler has been around for quite some time and has a lot documentation and device specific library functions. Yet, I feel that the HI-TECH C compiler is much more elegant and easy to program.

What about Basic and Pascal? These languages are good for high level tasks like business software, but they hold you too far from the intimate details referred to above. C also lets you get down and dirty and easily twiddle registers and bits — It is designed for efficiently dealing with hardware.

Finally, all C Compilers give you a get out of jail free card. They allow you to embed assembler directly into the C code. So, when you do feel the need to really optimise the hell out of a routine you can indulge yourself without causing too much of a headache. Before we start, all compilers listed below have free trial versions with a limited life and they all fully integrate into the Microchip MPLAB IDE (integrated development environment). So, you can always try them before you commit. CCS C Compiler CCS () produce a range of compilers that cover all 8 bit PICs (PIC10, PIC12, PIC14, PIC16, and PIC18 ) and a few of the higher spec chips (PIC24 and dsPIC). If you needed to summarise the CCS C Compiler in a word, that word would be “friendly”.

The compiler quietly handles all sorts of complications and provides you with a range of functions that handle most of the peripherals that come integrated on a PIC chip. For example, calling setup_timer_1() will do all the hard work in setting up timer 1. Sometimes the compiler can be too friendly, for example it will automatically set a I/O pin to input or output depending on how you use it in your code, but you can turn that off.

The best part of using this compiler is that you can install it, write some code, and the compiler will just do its job without you having to bother too much about the compiler (you might have problems with your code or the language, but that is another issue). The excellent support for the on chip peripherals and extensive libraries that CCS supply make the CCS Compiler by far the easiest to use. The only downfall with the CCS C Compiler is that it is not ANSI C compliant. It is close, but there are some constructs that will not compile. This is not generally a problem if you are writing your own code, as these constructs are relatively obscure, but it is a problem if you want to use code created by someone else. For example, the Microchip USB stack just will not compile using the CCS Compiler.