Rtos for Embedded Applications Ppt

7/29/2019 Rtos for Embedded Applications Ppt

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RTOS FOR EMBEDDED

APPLICATIONS


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Example Program: shellsort

gccgo shellsort shellsort.c

-g requests that the compiler and linker generate and retainsymbol information in the executable itself.

Place output in file shellsort.c. This applies to whatever sort of output is being produced,

whether it be an executable file, an object file, anassembler file or preprocessed C code.

If -o is not specified, the default is to put an executable filein a.out, the object file for source.suffix in source.o, itsassembler file in source.s, a precompiled header filein source.suffix.gch, and all preprocessed C source onstandard output.


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Debugging a Sample Program

./shellsort 4 6 3 1 7 8

./shellsort 4000 6000 3000 1000 7000 8000

Debugging using DDD (Data Display Debugger) ddd shellsort

Sourse Window: Display the source code

around the current execution point Command Tool: Buttons for commonly used

commands


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Tool Bar: Contains buttons for commands thatrequire and argument along with a windowfor entering the argument

Debugger Console: Lets you enter commandsdirectly to the inferior debugger's commandline. There are some operations that just workbetter at the command line

Status Line: Shows the current state of DDDand GDB


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select "View->Machine Code Window" to see

the assembly instructions (If required).

Configuring the debugger

Select "Edit->Preferences" from the main

menu. On the window that will appear, open

the "Source" tab (top of the window). Then,

check the "Display Source Line

umbers"option. Click OK to close the window.


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Next, select "Edit->GDB Settings" from the

main menu. In the window that pops up, scroll

approximately half way down through the list

of options, until you find the option

"Disassembly flavor. Change its value

to "Intel and click on CLOSE.

Finally, click on the "Edit->Save Options" menuto save these changes.


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Setting up breakpoints

The job of a debugger is to let us analyze aprogram's state at a certain point during its

execution. The state of a program is given by the

program's registers (EAX, EBX, etc), its stack

and memory images. A breakpoint identifies an instruction at which

execution of the program will be suspended.


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Notice that the debugger will top beforeexecuting the breakpoint instruction.

To set a breakpoint in DDD, right-click on the

instruction where you want to set the breakpoint,in the source window. Then, select "SetBreakpoint" from the popup menu. This is calledsticky break point because it stays there until

specifically we remove it. The breakpoint will appear as a "stop" sign on the

left of the instruction


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Debugging

First, open an execution window by selectingthe "View->Execution Window" menu or bypressing ALT+F9. This window will show anymessage that your program writes to standardoutput.

Then click on the "Run" button in the commandtoolbox on the right of the screen. As expected,

execution stops at line 40, where we set thebreakpoint. This is indicated by the green arrownext to the stop signal


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To see the current value of a variable, place

cursor over green arrow.

Yellow box appears with current value.

To execute the current line, click on the 'NEXT'

button on the command tool.

The arrow advances to the following line.

We can also set temporary break point, and it

goes away when the first time it is hit.


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At this point we can examine the state of the

program by first looking into its registers. This

is done by selecting the Status-

Registers menu. A window will pop upshowing the value of all of the program's

registers. Notice that you can keep this

window open as you continue your debugprocess later on.


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If instead of a register we are interested in examining aparticular memory location (such as msg), we can usethe "Data->Memory" menu. A window will pop upasking for the number of bytes to examine, and the

start memory address. In the example below wechoose to examine 5 bytes starting from the addressof msg. Because msg contains a string of characters, wechoose char as the format to print these 5 bytes. Whenyou click on "Display", a new frame inside the DDD

window will appear, showing the contents of memory.Notice that in below Figure we used &msg to indicatethe address of msg.


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It is often helpful, once reached a breakpoint, tocontinue execution of your program one instruction atthe time to observe how the status of the programchanges. The Next and Step commands in the toolbox

serve at this purpose. Open the registers window asexplained earlier, and observe how the values of theregisters change as we step through the instructions ofthe program using Step.

The difference between Next and Step is

that Next treats function calls (such as "callmyFunction") as a whole instruction, while Step jumpsinto the code of the function.


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To view the values of array say a, we can enter

following into argument window

a[0]@(argc-1) and click the print button.

The values appear in the debugger console.

Display option will display the variable with

name.

Rotate option can rotate the results to

required direction.


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Stack frame display: Clicking on step to step in

a function, the execution pointer in function

will move to the first line of function and

debugger console shows the argument passedto it.


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Setting up for remote debugging

Gdb server: gdbserver is a computer program thatmakes it possible to remotely debug otherprograms. Running on the same system as the programto be debugged, it allows the GNU Debugger toconnect from another system; that is, only theexecutable to be debugged needs to be resident on thetarget system, while the source code and a copy of the

binary file to be debugged reside on the developerslocal computer. The connection can be either TCP or aserial line.


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Connecting to gdb server:change to ddd folder; cd /usr/ddd

Starting gdb server:

gdbserver :1234 shellsort 4000 7000 2000 900

Gdb server responds with:process shellsort created; pid = 23

This indicates gdbserver has loaded theprograme and is waiting for debugging sessionto begin on the specified port.


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Debugging:

Start up DDD and to connect gdb server typethe following in debugger console window

target remote 192.168.0.200:1234 Output from gdb server indicates that target

programe has started and the coresspondingmessage in gdb window.

Use cont button insted ofrun in DDD.

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Rtos for Embedded Applications Ppt