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Khansokhua
Joined: 06 Nov 2021
Posts: 92
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| CCS C Compiler PIC16F877A |
 Posted: Sat Nov 06, 2021 6:26 am |
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Hello I am new at CCS C. I tried to "When I press a button F-A counter starts run on 7 SEGMENT DISPLAY. When I press the button second time A-F counter starts run on 7 SEGMENT DISPLAY. Third time I press the button again F-A ...(F-A,A-F,F-A...)" this application here is the code that I wrote:
| Code: |
const int FA[6]={0x71,0x79,0x5E,0x39,0x7C,0x77};
int i;
int a=2;
void main()
{
output_a(0x02);
while(true)
{
if(input(button) && a%2==0)
{
for(int i=0;i<=5;i++)
{
delay_ms(300);
output_d(FA[i]);
}
a++;
}
else if(input(button) && a%2==1)
{
for(int i=5;i>=0;i--)
{
delay_ms(300);
output_d(FA[i]);
}
a++;
}
}
}
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It goes first time F-A, second time A-F and then program does not work. I don't know why. At which point I made mistakes? If someone could enlighten me, I'll appreciate it. Thanks. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Nov 06, 2021 12:09 pm |
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You got a warning on this one:
| Quote: | | for(int i=5;i>=0;i--) // Warning: Condition always TRUE |
That's the reason. Find the problem and fix it.
Hint: With the PCM compiler, an 'int' is unsigned.
Hint: What does your loop count down to ?
Also, here's something I don't like:
You declare 'i' here for your loops:
| Quote: |
const int FA[6]={0x71,0x79,0x5E,0x39,0x7C,0x77};
int i;
int a=2; |
Then you declare it again inside your loops:
| Quote: | for(int i=0;i<=5;i++)
for(int i=5;i>=0;i--) |
In my opinion, get rid of the declarations inside your loops and
just have the one declaration at the top. |
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Khansokhua
Joined: 06 Nov 2021
Posts: 92
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| Posted: Sat Nov 06, 2021 2:50 pm |
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| Code: | const int FA[6]={0x71,0x79,0x5E,0x39,0x7C,0x77};
int i;
int a=2;
void main()
{
output_a(0x02);
while(true)
{
if(input(button) && a%2==0)
{
for( i=0;i<=5;i++)
{
delay_ms(300);
output_d(FA[i]);
}
a++;
}
else if(input(button) && a%2==1)
{
for( i=5;i>0;i--)
{
delay_ms(300);
output_d(FA[i]);
}
a--;
}
}
}
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So, it counts F to A and then A to E .But how it could be always true? What makes it? I can't see any reason.
for(int i=5;i>=0;i--) // Warning: Condition always TRUE
Also, how do I can understand the reason of be taken warnings?I just see redline.
Hint: With the PCM compiler, an 'int' is unsigned.
I really didn't understand it, pardon me sir. Thanks for your time. I’m absolutely delighted. |
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jeremiah
Joined: 20 Jul 2010
Posts: 1358
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| Posted: Sat Nov 06, 2021 5:03 pm |
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| Khansokhua wrote: |
So, it counts F to A and then A to E .But how it could be always true? What makes it? I can't see any reason.
for(int i=5;i>=0;i--) // Warning: Condition always TRUE
|
Well you didn't specify that the int i was "signed" so it was defaulted to unsigned. An unsigned number can never be less than 0, so the check "i>=0" is always true as the variable "i" can never be negative (it just wraps back around to max positive).
One of our coding standard rules is to always declare an integer based type with "signed" or "unsigned" specified. We found out the hard way once before when the compiler changed a default in a newer version. |
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Khansokhua
Joined: 06 Nov 2021
Posts: 92
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| Posted: Sun Nov 07, 2021 7:41 am |
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| Thank you so much. I clearly understood. |
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