[SOLVED] Question about programming trick

[alexan_e]

if it takes a few seconds then the input is probably read a few thousand time before the wrong data happens so I wonder why at that particular moment, do you have anything else in your code that could interfere in the reading process, any interrupt or some other peripheral?

 

[scorrpeio]

Hi guys,



I Have question in this scenario I have 8 parallel inputs w/ 8 switches and it is being pulled up by 8 resistors, so the normal values of my input read by the PIC when no switches pressed is 255.(all 8bit input are high/1)

the switch used is a push button switch.. NORmally open

when I press one switch located at PORTA.RA0 the input value will now be 255 -1 = 254..

the switch is momentary when I dont push it it will go back and the input value again will be 255.

so now the problem is I want to hold that value until the next activity of the switch. (the value 254)

I want to store that value inside a variable without losing it even if the switch is not press anymore

I tried something like this but after sometime inside a while 1 loop the value 254 disappear..

this is my code:

if(input != 255) //when any of the switch is pressed
store = input 

return store;

The above bold letters indicate that you are using 8 pins for switches...so I thought to use Intr on Change.

Now, I am confused...what is it exactly you are doing ;-)
Can you share schematic of hardware design?

 

[alexan_e]

something like

**broken link removed**

image source: **broken link removed**

 

[romel_emperado]

if it takes a few seconds then the input is probably read a few thousand time before the wrong data happens so I wonder why at that particular moment, do you have anything else in your code that could interfere in the reading process, any interrupt or some other peripheral?

I already disable all peripheral I am using..
I just only input shift registers..


okay.. I will update this thread with complete information.

I will upload here the simulation and the source code I am workin on..

---------- Post added at 10:25 ---------- Previous post was at 10:23 ----------

The above bold letters indicate that you are using 8 pins for switches...so I thought to use Intr on Change.

Now, I am confused...what is it exactly you are doing ;-)
Can you share schematic of hardware design?

the schematic posted by alexan_e is what exactly I am using..

whatever input received from that shift register will be copied to another port.. that is only I want to do..

I will upload here my work..

Thanks

 

[alexan_e]

you can try to validate the data before using them by comparing that the last x number of results are the same, you read the input very fast anyway so event a momentary button press will give a few hundred times the same result.
As an additional advantage you can probably use it to debounce your buttons in the real circuit

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Code C - [expand]
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int get_inputDATA()
{
    int data = 0,i;
    static int prev_data, count;  
 
    SPI_InLatch = 1; //load data
    delayus(1); 
    SPI_InLatch = 0;
 
    SPI_PLOAD = 0;
    delayus(1); 
    SPI_PLOAD = 1;
    
    
    for (i=7; i>=0; i--)
    {
        if(SPI_SI)
        data |= (1 << i); //store data received
        toogle_clock();
    }
 
    //return data;
    
    if (data==prev_data) count++;  // increment while getting the same data
    else {prev_data=data; count=0;} // if not same as previous data keep new data and reset counter
    
    if (count==10)  // if data was the same for 10 times or you can try more times
    {      
        count=0;
        if(data != 255)
        store = data;
        
    }
    
    return store;
 
}

---

Alex

 

[romel_emperado]

Hi Alexan_e..

Still the same value is not retaining.. Im attaching the proteus simulation and the source code..

 

[alexan_e]

in proteus simulation I get a watchdog expired warning every 2.3sec , this is probably the reason that the value is lost, a total reset

 

[romel_emperado]

what do you mean? in my simulation?

---------- Post added at 12:22 ---------- Previous post was at 12:21 ----------

okay.. I see it now.. I will try to hardcode the configuration bits and disable the watchdog timer.

 

[alexan_e]

yes, check the simulation log while running the simulation

 

[romel_emperado]

I see it now.. it's weird I can't disable the WDT... it's weird . WDT is not running in simulation in some PIC simulation..

 

[alexan_e]

I have no idea, maybe it is a bug of proteus model, if the watchdog is not working in reality then the result will be correct

---------- Post added at 13:41 ---------- Previous post was at 13:40 ----------

if the watchdog is not running in your ide simulator then it is probably a proteus model bug

 

[romel_emperado]

yes.... WE wasted time because of this.. now I lear again from you.. next time I will always visit the protues log... Thanks so much

I spent almost 24hours for this problem...

 

[romel_emperado]

hi,, the problem was already spotted.. the watchdog timer keeps reseting the MCU.. it's weird ..

---------- Post added at 14:05 ---------- Previous post was at 13:45 ----------

Problem solved!!!

for future reference to other members. if you are working with PIC18f452 in proteus YOU NEED TO DISABLE THE WATCHDOG TIMER...

special thanks to Alexan_e..

thanks so much..