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scanan
Joined: 13 Aug 2004
Posts: 59
Location: Turkey
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| structures |
 Posted: Fri Dec 20, 2024 7:01 am |
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hi I've tried this kind of structure on ccs pic 4.114 when compiling
get expression must evaluate to a constant , expecting declaration, expecting a (, . is it possible to construct this kind of struct in ccs.
typedef struct {
int1 up1;
int1 down1;
int1 up2;
int1 down2;
int1 left1;
int1 right1;
int1 LR_2;
int1 north1;
int1 south1;
int1 NS_2;
} IOpin_t;
IOpin_t IOpins = {
.up1 = up1,
.down1 = down1,
.up2 = up2,
.down2 = down2,
.left1 = left1,
.right1 = right1,
.LR_2 = LR_2,
.north1 = north1,
.south1 = south1,
.NS_2 = NS_2
};
cheers
_________________
Dr Suleyman CANAN
R&D Electronic Engineer
https://suleymancanan.wordpress.com
Do whatever you do with amateur spirit -
But always feel professional. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19552
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| Posted: Fri Dec 20, 2024 7:46 am |
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No.
Use of the structure member operator like this is not originally C!.....
It is part of C++, that many C's now allow. GCC for example. It is now part
of the newer ANSI standard, but later than CCS supports.
You can write to the individual members at declaration just by putting the
values separated by commas, but values have to be constants in your version.
4.114, is very old. Some more sophisticated initialisations are supported in
more recent versions, but not this. |
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temtronic
Joined: 01 Jul 2010
Posts: 9246
Location: Greensville,Ontario
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| Posted: Fri Dec 20, 2024 9:55 am |
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just a comment...
It may be 'better' to have 'unused filler' bits to make structure to be 8 bits or 16 bits
Usually you can arrange bits into logical groups.
At one time there was a problem, accessing bit across byte 'boundaries'. |
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allenhuffman
Joined: 17 Jun 2019
Posts: 580
Location: Des Moines, Iowa, USA
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| Posted: Fri Dec 20, 2024 7:38 pm |
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Does int1 turn in to something other than a byte? I thought I just saw it in one of the header files and it was a bool?
_________________
Allen C. Huffman, Sub-Etha Software (est. 1990) http://www.subethasoftware.com
Embedded C, Arduino, MSP430, ESP8266/32, BASIC Stamp and PIC24 programmer.
http://www.whywouldyouwanttodothat.com ?
Using: 24FJ256GA106, 24EP256GP202 and 24FJ64GA002. |
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jeremiah
Joined: 20 Jul 2010
Posts: 1358
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| Posted: Fri Dec 20, 2024 11:27 pm |
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| allenhuffman wrote: | | Does int1 turn in to something other than a byte? I thought I just saw it in one of the header files and it was a bool? |
It can yes. The PIC supports general bit set/test/clear/etc instructions, so the compiler will often try to optimize int1 variables using those. Sometimes it will promote to a byte, but it depends on the situation. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19552
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| Posted: Sat Dec 21, 2024 1:05 am |
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int1, is a bit in a byte.
As Jay says, the compiler will optimise to use bit instructions where these
exist, and combines multiple ones to form a byte.
Where there is an issue, is when using bit fields in a structure, and these
fields cross a byte boundary (on PIC12/14/16/18), or a word boundary
(on PIC 24/30/33). This can cause issues. So (for example):
| Code: |
struct {
int bits :4;
int more bits:5;
} variable;
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or when using int1's and mixing with other values:
structure {
int1 bit;
int value;
} variable;
[/code]
If is better in both cases to try to ensure that you declare the big values
first and avoid declarations that cross the chip's basic type sizes.
The first, the compiler will warn about, and the second on later compilers
is fine, with the compiler just leaving 7 bits of space. However just better
not to actually rely on this behaviour, especially with a compiler as old as
yours. |
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