Hi all,

Could anybody help me or guide me to write a better ISR code which use
lesser memory and compiles smaller hex file.The problem I am facing is if
use too many 'if else' conditions in my ISR the hex file compiles shoots t
18Kb whereas if i use one or two conditions only the hex file is around 5K
.I want my compiled Hex file to be around 8-10 Kb.Below is my code of ISR.


/
************************************************** *************************************
// Low Priority Interrupt
/
************************************************** *************************************
void HIGH_ISR (void);
#pragma code high_vector_section=0x08
void high_vector (void)
{
_asm
goto HIGH_ISR
_endasm
}
#pragma code
#pragma interrupt HIGH_ISR
void HIGH_ISR (void)
{

if (PIR1bits.RCIF == 1) // If USART Rx Flag is set
{
UART_Data.Input = ReadUSART(); // Get character USART module


if(UART_Data.Input == 0x11)
{
EE_Address = 0xAA;
EE_Data = Current_time;
Write_EEPROM();

EE_Address = 0xAB;
EE_Data = Current_ports;
Write_EEPROM();
}

else if(UART_Data.Input == 0x12)
{
Read_EE();
printf("\nCurrent Time settings = %d", eet);
printf("\nCurrent Port settings = %d", eep);
}

else if(UART_Data.Input == 0x13)
{
printf("\nCurrent Time settings = %x", Current_time);
}

else if(UART_Data.Input == 0x14)
{
printf("\nCurrent Port settings = %x", Current_ports);
}

else if(UART_Data.Input == 0x15)
{
Current_time = Default_time;
Current_ports = Default_ports;
delay = (Current_time*5);
// Set_Port_Time();
printf("\nCurrent Port settings = %x", Current_ports);
}

else if((UART_Data.Input >= 0x21) && (UART_Data.Input <= 0x2A))
{

Current_ports = UART_Data.Input;
printf("\n%x",UART_Data.Input);
}

else if((UART_Data.Input == 0x31) || (UART_Data.Input == 0x33) |
(UART_Data.Input == 0x35) || (UART_Data.Input == 0x37) || (UART_Data.Inpu
== 0x39))
{
Current_ports = UART_Data.Input;
printf("\n%x",Current_ports);
}

else if(UART_Data.Input >= 0x80)
{
Current_time = ((UART_Data.Input) & (0x7F));
printf("\nTiming Selected = %dms",Current_time*50);
delay = (Current_time*5);
// Set_Port_Time();
}


else if(UART_Data.Input < 0x80)
{
PORTB = 0x00;
PORTC = 0x00;
ports = ((UART_Data.Input) & (0x0F)) ;
if( (ports >= 1) && (ports <= 10) )
{
Current_ports = ports;
printf("\nPorts Selected higher priority intr
%d",Current_ports);
}
else{
printf("\n Enter valid ports number (1-10) \n");
}
}


UART_Data.Flag_UART_RX = 1;
PIR1bits.RCIF = 0; // Clear the interrupt flag
}
}


Could anybody help me over this I desperately need to reduce my code siz
to flash to MCU.

Thank you all .Appreciate if anybody can guide over an alternativ
strategy for 'if else'.

lallisidhu ha scritto:
You can try to refactor your code to use a switch, sometimes the
compiler is smart enough to convert your code to a table jump.
Or you may try to implement a lookup table instead of manually check
for every possible UART_Data.Input value.

Ciao
--
_|/ Francesco Sacchi - Develer S.r.l., R&D dept.
|\ http://www.develer.com/ - http://www.bertos.org

On Sat, 17 May 2008 07:02:23 -0500, "lallisidhu"
<lallisidhu@gmail.com> wrote:

For one thing, you're using stdio library functions inside the ISR. In
your (unspecified) architecture, is printf() reentrant?

Even if it is, you might want to separate [read the UART] from [handle
the results of the read] into foreground and background processes.
Have the ISR simply read and queue the characters, let the main
execution thread handle the characters.

--
Rich Webb Norfolk, VA

lallisidhu schreef:
If at all possible consider removing printf() from all of your code.
Chances are that the printf() code consumes many times more memory than
the if-else-if code in your ISR.

lallisidhu wrote:

For starters, you're doing way too much work inside your ISR. As a rule
of thumb, ISRs shouldn't usually have to call more than one other
function. If their jobs are big enough to be delegated to a separate
function, an ISR shouldn't be trying to do more than one of them.

Stuff like calling printf() or performing an EEPROM write operation is
generally out of the question for an ISR. You'd be blocking further
interrupts for far too long.

I rather doubt that the number of conditionals, in and of itself, is the
root cause of that code explosion. It's much more likely that what
you're doing in all those branches that's killing you.

On May 17, 2:40 pm, Dombo <do...@disposable.invalid> wrote:
I guess, the printf() taking up memory. Is look like you are printing
a string and a number in each printf(). can you define two variables,
one for string and one for number. and assign appropriate values in
the if clause. after the if clause call the printf() to print the
string variable and number variable. in that case you are calling
print() only once.
it might help, just a suggestion.

Thanushan

On Sat, 17 May 2008 07:02:23 -0500, lallisidhu <lallisidhu@gmail.com> wrote:
I think I'd recommend running your compiler against both (all) versions
of your code and generating assembler/object listings. With those in
hand (or on acreen) you can see where and how the additional memory
is being used.

If you're not familiar with this, check your compiler's options, the
compiler manual, or the online help as appropriate. Examining the
code generated by one's compiler can give you a good feel for how
your C code maps into bytes/words of flash.

Hope this helps...


Frank McKenney
--
You cannot depend on your eyes when your imagination is out
of focus. -- Mark Twain
--
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
Munged E-mail: frank uscore mckenney ayut mined spring dawt cahm (y'all)