EE C Program Elements

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Frederick Todd
6 years ago
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1 EE 1910 C Program Elements

2 Development process need Requirements Specification Program Flow Pseudo Code Code Development Tool Chain Test Executable Code Production 2 tj

3 Requirements Specification Identify what the system must do to solve the problem Over specify: Higher cost Longer development time Under specify Don t solve problem Customer does not accept the solution No design solutions should be assumed at this stage Maximize the design space 3 tj

4 Program Flow / Pseudo Code Hierarchical system design Up/Down sub-system design Focus on general structure not too specific Basic flow diagram blocks Entry / Exit Process Block (actions) Decision Block Input Output 4 tj

5 Program Flow Keyless Start Enter Start Routine Sense for Key No Button Push Yes No Key in range Yes Sense for Button Push Engage Starter Exit 5 tj

6 Program Flow Keyless Start Enter Start Routine No Sense for Key Key in range Yes Sense for Button Push No Button Push Yes Engage Starter Exit Why not this 6 tj

7 Pseudo Code Keyless Start In an infinite loop: If Key present If button pushed engage starter end end 7 tj

8 C program first look Preprocessor Directives Global Declarations int main (void){ Local Declarations } Statements Additional Functions Additional Functions 8 tj

9 Preprocessor directives Provide information to the tool chain Additional files to include Name definitions Constant definitions Always start with a # 9 tj

10 Preprocessor directives Examples - #include <stdio.h> Include the contents of library file stdio.h along with my code #define PI Everywhere I used PI, replace it with #define LEDPIN 9 Everywhere I used LEDPIN, replace it with 9 Common to define which pin LED is attached to Allows changes in 1 place instead of all through the code 10 tj

11 Global Declarations Define variables that can be seen throughout the program Examples int age Define a variable age float InterestRate = Define a variable InterestRate and initialize it to tj

12 Main Code section containing your top level program code Program flow is controlled by main Required Can only be 1 main in your program Local Declarations Define variables that can be seen inside of main Statements The top level program code 12 tj

13 Other functions Functions are sections of code defined to do a specific task They are called by main or other functions Can take values in and provide values out Good programming uses main for control and uses functions for getting things done 13 tj

Simple Program /* circle.c Calculate the area and circumference of a circle Created by tj Rev 0, 11/15/16 */ #include <stdio.h> #define PI 3.

14 Simple Program /* circle.c Calculate the area and circumference of a circle Created by tj Rev 0, 11/15/16 */ #include <stdio.h> #define PI int main(void){ setbuf(stdout, NULL); // disable buffering // Local variables float radius; float circumference; float area; // Get input for radius printf("please enter a value for radius: "); scanf("%f", &radius); // Calculate circumference and area circumference = 2 * PI * radius; area = PI * radius * radius; // Output results printf("circumference = %f\n", circumference); printf("area = %f\n", area); return 0; } 14 tj

15 Tool Chain Code Entry PreProcessor Compiler Assembler Linker Loader 15 tj

16 Tool Chain Code Entry CodeEntry filename.c Text editor Integrated Development Environment Energia Code Composer Eclipse 16 tj

17 Tool Chain Preprocessor PreProcessor Deals with any commands starting with # Tells the tool chain to include additional libraries Replaces any defines throughout the code Expands macros throughout the code Manages any conditional defines 17 tj

18 Tool Chain Compiler Compiler Converts c-code to assembly language Assembly language Architecture specific programming language Direct access to specific registers, commands, memory ldi R2, 5; // load register R2 with the value 5 sts R2, 0x0200; // copy the value in R2 to memory location 0x200 add R2, R1; // add the values of R2 and R1 and store in R2 18 tj

19 Tool Chain Assembler Assembler Converts assembly language to machine language Result is an object file (file.o) Machine language Part specific programming language Binary representation that the processor understands // load register R2 with the value // copy R2 to memory location 0x // add R2, R1 and store in R2 19 tj

20 Tool Chain Linker Linker Combines the machine language code from your program with all included libraries Configures all the code in memory Aligns code segments Makes connections where necessary (function calls) Assigns variables spots in memory Creates an executable file - file.out (file.exe for windows systems) 20 tj

21 Tool Chain Loader (programmer) Loader Creates whatever environment is necessary on the executing machine Loads the executable program Starts the program 21 tj

22 Energia Very simple IDE Code creation stored in (file.ino) actually an Arduino file format Verify / Compile Check syntax pre-processor compiler linker Indicates how much of the program memory is used Upload Loads the linked file onto the MSP chip (Program Memory) Restarts the MSP chip 22 tj

23 Energia Basic program (sketch) Blink.ino /* Blink The basic Energia example. Turns on an LED on for one second, then off for one second, repeatedly. Change the LED define to blink other LEDs. Hardware Required: * LaunchPad with an LED This example code is in the public domain. */ // most launchpads have a red LED // #define LED RED_LED // the setup routine runs once when you press reset: // void setup() { // initialize the digital pin as an output. pinmode(led, OUTPUT); } // the loop routine runs over and over again forever: // void loop() { digitalwrite(led, HIGH); // turn the LED on (HIGH is the voltage level) delay(1000); // wait for a second digitalwrite(led, LOW); // turn the LED off by making the voltage LOW delay(1000); // wait for a second } 23 tj

24 Energia Bridging the gap between Energia (Arduino) and C Sketches are Cpp functions called by the Energia main.cpp program // Main.cpp (abbreviated) #include <ti/runtime/wiring/energia.h> int main(void){ setup(); for (;;) { loop(); } } return 0; 24 tj

Function I/O. Function Input and Output. Input through actual parameters. Output through return value. Input/Output through side effects

Function I/O. Function Input and Output. Input through actual parameters. Output through return value. Input/Output through side effects Function Input and Output Input through actual parameters Output through return value Only one value can be returned Input/Output through side effects printf scanf 2 tj Function Input and Output int main(void){