Sometimes you might like to manipulate the members of C structures in a more generalized way. This can be done by using pointer reference to structure. Normally it is easier to pass a pointer to a structure than passing the entire structure to function. Structure pointer can be declared very easily: For instance: we can assign the first structure address to the structure pointer like this: now we can access the first structure members by using structure pointer: or we can write Structures can contain member pointers to other structures or structures of the same type. This way, we can create lists – dynamic structure: This way, you can assign the pointer with the address to another structure: Read more about dynamic structures in C tutorials on the internet.
The MPX5100 series piezoresistive transducer is a state-of-the-art monolithic silicon pressure sensor designed for many applications. Still, particularly it is convenient to interface to a microcontroller or microprocessor with ADC inputs. This is thin-film metallization and bipolar processing to provide an accurate, high-level analogue output signal proportional to the applied pressure. More details can be found here MPXV5100 This sensor measures differential pressure comparing to atmospheric so when there is no pressure applied it shows 0kPa;
There are many situations when you might need to measure temperatures or trigger some events due to temperature changes. It is very convenient to have these values in a digital format. Then you can transfer digital values to the microcontroller to process data or just to display on the LCD screen. AD7416 Sensor description This is a 10-bit digital temperature sensor that can measure temperatures in the range interval -40 to 125ï‚°C). Temperature conversion ADC has 15 conversion times. The sensor can be supplied from 2.7 to 5.5V, so it is no problem to connect directly to ARM microcontrollers. Data is transferred through the I2C serial interface. The more detailed description and datasheet can be downloaded from Analog devices page: AD7416. Here you find a simple routine where the Atmega8 microcontroller reads sensor data decodes temperature value and displays it on a 2×16 LCD display.
AVRISP is a very popular Parallel port programmer for flashing AVR type microcontrollers. Earlier I used programmer connected to com port, but frequently I needed this port for other purposes; I decided to make it work on the parallel port. The programmer on a parallel port is much simpler than connected to a serial port because there is no needed voltage adapter like MAX232. You can only connect your MCU directly to the port. But for safety reasons, there is good practice to use buffer ships like 74HC244. The header for programmer I used standard 6 pin ISP header.
After the release of AVRStudio4, there is the ability to integrate the AVR-GCC compiler in it. As you know AVR studio has only assembler compiler- debugger. Integration of AVR-GCC is done by the plugin. The plugin detects AVR-GCC by itself, you don’t have to bother. What do we get from it? Of course a full set of good tools comparable to commercial. The convenient user interface, automatic makefile generation, visual debugging by watching processors register, or even you can flash the chip. We can say that abilities are: 1. Compilation, setting parameters, automatic AVR-GCC detection; 2. Graphical User Interface – convenient project setting; 3. Tree-like project view; 4. Project can comply with predefined configurations; 5. Convenient error handling; 6. Ability to use external makefiles; 7. Map and List file generation; 8. Plugin inspect connections among source files (c and h files which are not part of the project); 9. User can work with c or ASM projects in one environment. Other documentation can be found in AVRStudio help files. This feature is well documented.
This time I decided to lay down some information on using the AVR-GCC compiler. I will not rewrite what’s in documentation is already written, but write down some issues that can help you start using this amazing tool. Introduction Most AVR programmers probably had a question in their mind about what compiler to use for their designs. The choice is huge. You can use commercial ones like IAR, CodeVision, ImageCraft. These compilers come with convenient GUI’s, code generators. But you have to buy a license to use them. So if you are going to do a low-budget project, the best choice is to use the open-source compiler GCC. This is the most successful open-source compiler in the world. The AVR platform is called AVR-GCC. The compiler itself has no graphical interface. Everything can be done in the MSDOS command line or the Linux command line. To make it easier to compile a project, there are makefiles used. GNU compilers usually are using UNIX style make files. This file can be run with the make.exe program. In reality, you don’t have to write makefiles – there are ready templates to use.Everyone may agree that using a compiler in the command line…
The main thing that microcontrollers does is operates with data. Microcontrollers do four main operations: adds, abstracts, multiplies, and divides (+,-,*,/). division can be split into the division “/” and modulus operation “%.” For instance, i1/i2 is an integer division. Another part of the operators is Relation operators. They are used for boolean conditions and expressions. Expressions with these operators return true or false values. Zero is taken as false and non zero value as true. Operators may be as follows: <, <=, > >=, ==, !=. The priority of the first four operators is higher than that of the latter two operators. These operators are used in relational expressions such as: Note that the equality operator is == and not =. ‘=’ is an assignment operator. If you want to compare a and b for equality, then you should write a == b, not a = b because a = b means you are assigning the value of b to a, as shown in.
Constant value is understandable as nonchangeable value like PI=3.141592… value in math. Usually, you use constants in your programs, but don’t realize that they are constants. For instance: x=x+3; The number 3 is a constant which will be compiled directly in addition operation. Constants can be character or string. Like in function printf(“Hello World\n”); “Hello World” is a string constant that is placed in program memory and will never change. It is usually recommended to declare constants by using identifier with reserved word const: const int No=44; Identifying the variable as constant will cause the compiler to store this variable in program memory rather than in RAM, thus saving space in RAM. If special functions are used, then constants can also be stored in EEPROM memory.
C language is a function-based programming language. C program itself is a function. Usually, parameters to the C function are passed as arguments. The function consists of a name followed by the parentheses enclosing arguments or an empty pair of parentheses if there are no arguments required. If there are several arguments, they are separated by commas. The mandatory part of the C program is the main function. This function must be included in every program because it is the first function run after its execution. Lets take an example: This is an elementary C program, but it contains all the necessary elements. Let’s examine a little bit about what we have written here…
There is no doubt that everyone faces C language when programming microcontrollers. This is the most popular language among hardware programmers. There are plenty of books about this language – you have to open and read. This article is not about language basics, but c language’s effectiveness in embedded systems touched. Quite often, you can find good examples of effective algorithms: faster code performance and code size. To write a good optimal algorithm, you have to know the structure of the compiler. Of course, we will not analyze compilers, but we can look through a few rules and tricks and achieve an optimal algorithm.