Programming syntax and Data sheet

Neils Lecture summary !

Our assignment for the week to understand and Read a microcontroller data sheet.Program your board to do something, with as many different programming languages and programming environments as possible.

Embedded C Programming is the soul of the processor functioning inside each and every embedded system we come across in our daily life, such as mobile phone, washing machine, and digital camera.

illusrated about the workflow

Each processor is associated with an embedded software. The first and foremost thing is the embedded software that decides functioning of the embedded system. Embedded C language is most frequently used to program the microcontroller.

Earlier, many embedded applications were developed using assembly level programming. However, they did not provide portability. This disadvantage was overcome by the advent of various high level languages like C, Pascal, and COBOL. However, it was the C language that got extensive acceptance for embedded systems, and it continues to do so. The C code written is more reliable, scalable, and portable; and in fact, much easier to understand.

About C Language

C language was developed by Dennis Ritchie in 1969. It is a collection of one or more functions, and every function is a collection of statements performing a specific task.

C language is a middle-level language as it supports high-level applications and low-level applications. Before going into the details of embedded C programming, we should know about RAM memory organization.

Salient features of the language

C language is a software designed with different keywords, data types, variables, constants, etc.

Embedded C is a generic term given to a programming language written in C, which is associated with a particular hardware architecture.

Embedded C is an extension to the C language with some additional header files. These header files may change from controller to controller.

The microcontroller 8051 #include is used.

The embedded system designers must know about the hardware architecture to write programs. These programs play prominent role in monitoring and controlling external devices. They also directly operate and use the internal architecture of the microcontroller, such as interrupt handling, timers, serial communication and other available features.

Differences between C and Embedded C

C Programming	Embedded C Programming
Possesses native development in nature.	Possesses cross development in nature.
Independent of hardware architecture.	Dependent of hardware architecture.(i.e; microcontroller or other devices)
Used for Desktop applications,OS and PC memories.	Used for limited resources like RAM,ROM and I/O peripherals on embedded controller.

The basic additional features of the embedded software

Data types

The data type refers to an extensive system for declaring variables of different types like integer, character, float, etc. The embedded C software uses four data types that are used to store data in the memory.

The ‘char’ is used to store any single character; ‘int’ is used to store integer value, and ‘float’ is used to store any precision floating point value.

The size and range of different data types on a 32-bit machine is given in the following table. The size and range may vary on machines with different word sizes.

Size

Data Type	Range
Char or singed char	1 byte	-128 to +128
Unsigned char	1 byte	0 to 255
int or signed int	2 byte	-32768 to 32767
Unsigned int	2 byte	0 to 65535

Keywords

There are certain words that are reserved for doing specific tasks. These words are known as keywords. They are standard and predefined in the Embedded C.

Keywords are always written in lowercase. These keywords must be defined before writing the main program. The basic keywords of an embedded software are given below:

Name	Function
sbit	Accessing of single bit
bit	Accessing of bit addressable memory of RAM
sfr	Acessing of sfr register by another name

sbit: This data type is used in case of accessing a single bit of SFR register.

Syntax: sbit variable name = SFR bit ;

Ex: sbit a=P2^1;

Explanation: If we assign p2.1 as ‘a’ variable, then we can use ‘a’ instead of p2.1 anywhere in the program, which reduces the complexity of the program.

Bit: This data type is used for accessing the bit addressable memory of RAM (20h-2fh).

Syntax: bit variable name;

Ex: bit c;

Explanation: It is a bit sequence setting in a small data area that is used by a program to remember something.

SFR: This data type is used for accessing a SFR register by another name. All the SFR registers must be declared with capital letters.

Syntax: SFR variable name = SFR address of SFR register;

Ex: SFR port0=0x80;

Explanation: If we assign 0x80 as ‘port0’, then we can use 0x80 instead of port0 anywhere in the program, which reduces the complexity of the program.

SFR Register: The SFR stands for ‘Special Function Register’. Microcontroller 8051 has 256 bytes of RAM memory. This RAM is divided into two parts: the first part of 128 bytes is used for data storage, and the other of 128 bytes is used for SFR registers. All peripheral devices like I/O ports, timers and counters are stored in the SFR register, and each element has a unique address.

The Structure of an Embedded C Program

comments

preprocessor directives

global variables

main() function

{

local variables

statements

…………..
…………..
}

fun(1)

{

local variables

statements

…………..
…………..
}

Comments: In embedded C programming language, we can place comments in our code which helps the reader to understand the code easily.

C=a+b; /* add two variables whose value is stored in another variable C*/

Preprocessor directives: All the functions of the embedded C software are included in the preprocessor library like “#includes, #defines”. These functions are executed at the time of running the program.

Global variable

A global variable is a variable that is declared before the main function, and can be accessed on any function in the program.

#include < reg51.h > sbit a=p1^5; /* global declaration*/ void main() {

Global Variable example

Local variable

A local variable is a variable declared within a function, and it is valid only to be used within that function.

#include < reg51.h > void main() unsigned int k; /* local declaration*/ a=0x00; while(1) {

local Variable example

Main () function

The execution of a program starts with the main function. Every program uses only one main () function.

Advantages of embedded C program

Its takes less time to develop application program.

It reduces complexity of the program.

It is easy to verify and understand.

It is portable in nature from one controller to another.

Now let's understand the Data Sheet

i have gone through the datasheet of the ATTiny44

undersatnd the programming pinouts from the data sheet

the data sheet can be obtained here

Softwares used to program

i have learned the Embeded C Programming first and i know the arduino programming language i have used it for programming the board

Blink Programming Using AVR C

#include < avr/io.h > // Importing the avr/io library (as stdio.h in the normal C) #define F_CPU 20000000 //telling the frequency, here the 20Mhz of the Resonator #include < util/delay.h > // Importing library for delay (For blinking LEDs we need delay) int main(void) { DDRA = 0b00000100; //Set Pin PA2 on PORT A as output while(1) { PORTA = PORTA | (0b00000100); //PA2 is 3 from left _delay_ms(1000); // delay of 1 second PORTA=(0x00); // Make all pins in port A low _delay_ms(1000); // delay of 1 second } }

i have used the yadu (our instructors ) ComflashComflash Utility

installed the compflash

Inorder to compile in avr-gcc and flash the program on attiny44, we may need to run certain commands from the terminal. One of our instructor, Mr.Yadu has developed one User Interface in python language for easy compiling and flashing, it's called Compflash. Its available in the githublink, Compflash. I just cloned it in my PC. It requires certain dependancies, you can install it in your PC using commands. Once cloned,open terminal from the cloned directory, then type python compfalsh.py. It will open the GUI of comp flash like this.

while using the comflash

Programming using Arduino IDE

Arduino is an open-source platform used for building electronics projects. Arduino consists of both a physical programmable circuit board (often referred to as a microcontroller) and a piece of software, or IDE (Integrated Development Environment) that runs on your computer, used to write and upload computer code to the physical board. There are a large collection of tutorials are available on Arduino, out of which ,I found the following tutorial is good to know more about Arduino.

Ardunio is basically AVR C with an extra layer on top of it. For beginners like me Arduino is relatively easier to learn than AVR C. This is because in the Arudino IDE most of the common tasks we have to do are written as functions and stored in the Arduino library. This makes it easier for beginners as all we have to is call the right functions and the program will work accordingly. But a downside of this is that, the chip will work much slower than if it was programmed with AVR C the reason is that Arduino loads a lot of unused libraries into the chip which will waste many clock cycles. Another problem is the size of the program itself, this will be much larger in comparison with AVR C program.

After Installing Arduino in Linux, I plan to program my board using Fab ISP through arduino IDE. Arduino IDE supports all default Arduino boards, but in order to work with external boards, we have to first add the boards through the board manager.

You can follow this tutorial to add the Attiny44 board to the Arduino IDE.

Here are the steps,

Open the preferences dialog in the Arduino software.

Find the “Additional Boards Manager URLs” field near the bottom of the dialog.

Paste the following URL into the field (use a comma to separate it from any URLs you’ve already added):
https://raw.githubusercontent.com/damellis/attiny/ide-1.6.x-boards-manager/package_damellis_attiny_index.json

Click the OK button to save your updated preferences.

Open the boards manager in the “Tools > Board” menu.

Scroll to the bottom of the list; you should see an entry for “ATtiny”.

Click on the ATtiny entry. An install button should appear. Click the install button.

Close the boards manager. You should now see an entry for ATtiny in the “Tools > Board” menu.

Blinking LED using Arduino IDE.

Now you have successfully added the board, you can begin programming.

Arduino has some example programs to get you started. I went through the LED blink program and edited the source code. I changed the pins of the program to correspond to the pins on my board after referring the Arduino pin out diagram of ATtiny. The program was flashed successfully after burning the Arduino bootloader.

Blinking LED using Arduino IDE.

The program size was 952 bytes, When compared to the same program written in AVR C (457 bytes), is almost double. This is the extra overhead I talked about when using Arduino. Its useful for prototyping quick projects but not suitable for running finished products.

Conclusion

I had great time while programming in C and Arduino Programming Language

I am able to Use multiple protocols

I am able to understand the interup programming

I was able to debug the errors in programming

I understand what is the benfits of using the Embedded programming