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pet007
Joined: 25 Jan 2023 Posts: 21
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Pointer to 2D array in function call |
Posted: Wed Jan 25, 2023 12:34 pm |
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Hello, pls, how to use pointer to 2D array stored in ROM in function call ?
When I used Font array in function as static 2D array, it works well and fast, but I'd like to use various 2D arrays in function call. Thanks a lot.
MCU: 18K26K22
Edit: so this one works, but I have to insert size of 2D array in function call:
Code: |
rom u8 Ravie16x16[16][33] = {
0x07, 0x00, 0x00, 0x......
0x0D, 0x01.............
void Nokia_BigUni(rom u8 *FONT[16][33],u8 px,u8 py, int8 c) {
u8 char_pos,i;
u8 CharLen;
if(c < 46) c=46;
if(c > 57) c=57;
char_pos=(c-46);
CharLen = *FONT[char_pos][0];
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Ttelmah
Joined: 11 Mar 2010 Posts: 19540
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Posted: Thu Jan 26, 2023 1:52 am |
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That is standard and correct.
In C, an array passed to a function, does not 'know' anything about it's
dimensions. It 'decays' to just a pointer. You have a series of choices:
1) Pass as a single dimensional array of pointers. Each pointer then
points to the second list of elements.
2) Pass as a fixed size array known at compile time (this is what you
are now doing). Technically it is only the last dimension that needs to
be known.
3) Pass as a single dimensional array, and pass the size of the elements
as another variable. Then handle the addressing yourself.
Get a standard C textbook. It'll explain this. |
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pet007
Joined: 25 Jan 2023 Posts: 21
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Posted: Thu Jan 26, 2023 1:55 am |
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Thanks, yes, now it's clear for me. |
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pet007
Joined: 25 Jan 2023 Posts: 21
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Posted: Thu Jan 26, 2023 1:53 pm |
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So this code below works, as Ttelmah said:
('cols' is length of each "row" in 2D array, listed in 1st post.)
Code: |
void Nokia_BigCh(rom u8 *FONT, u8 Cols, u8 px,u8 py, int8 c) {
u8 i;
u16 char_pos;
u8 CharLen;
if(c < 46) c=46;
if(c > 57) c=57;
char_pos=(u16)(c-46)*(u16)Cols;
CharLen = FONT[char_pos][0];
Nokia_cmd(0x22);
Nokia_gotoXY(px,py);
CharLen = CharLen << 1;
for(i=1;i < CharLen;i=i+2) {
Nokia_write(FONT[char_pos][i]); Nokia_write(FONT[char_pos][i+1]);
....
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For simpler call I am using this definition also:
Code: |
#define Nokia_RevieNum(x,y,c) Nokia_BigCh(Ravie16x16,33,x,y,c+46)
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so in main.c :
Code: |
Nokia_RevieNum(pos_x, pos_y, digit); // digit: 0-8
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