Game Boy Advanced Home brew image issue in C

Question

I am making a home brew gba game just for fun and I have run into a little problem, i can draw a image on the screen fine, and i can read key input, expect when i try to display a different image when the user presses ENTER which is mapped to the START button in the Emulator I am using (Visual Boy Advanced) nothing happens, there are no errors when I compile the game so I have no clue what is wrong, please note I have only just got into this and I don't know much, I someone knows how to get this to work I would be very happy:D

Here is my code:

typedef unsigned short u16; // two type definitions
typedef unsigned long u32;

#include "ppic.h"
#include "ui.h"
#include "keypad.h"

#define REG_DISPCNT    *(u32*)0x4000000
#define MODE_4 0x4
#define BG2_ENABLE 0x400
u16* paletteMem = (u16*)0x5000000;  
u16* videoBuffer = (u16*)0x6000000; 

void PlotPixel(int x,int y, unsigned short int c) 
{
        videoBuffer[(y) *120 + (x)] = (c);
}

int main(void)
{
        int x, y, blockX, blockY, loop; 

REG_DISPCNT = MODE_4 | BG2_ENABLE; 
for(loop = 0; loop < 256; loop++)   
    paletteMem[loop] = ppicPalette[loop];
while (1) // run forever
{
            if(!((*KEYS) & KEY_START))
            PlotPixel(x,y,uiData[y*120+x]);

    for(y = 0; y < 160; y++)
    {
        for(x = 0; x < 120; x++)
        {
            PlotPixel(x,y,ppicData[y*120+x]);
        }
    }

}
return 0;
}

ui.h is the header file for the image that I want to display, ppic.h is the header file of the image that I show on startup.

The statement after the `if` condition seems to set only one pixel. Is this the desired effect? — Codor, May 23 '14 at 08:08
if you are talking about uiData, that is a method in ui.h that contains data for each pixel — user3349095, May 23 '14 at 19:41
I think I was mistaken. Do I get this right - if no key is pressed, then one individual pixel should be plotted, if start is pressed, the data from `ppicData` should be shown? — Codor, May 23 '14 at 20:10
no, if that is what I am doing then please correct me im kinda new to this — user3349095, May 23 '14 at 21:08

score 1 · Accepted Answer · answered May 24 '14 at 18:16

If the condition in the if statement is true, no looping over the x and y coordinate is done, instead only one pixel gets set. Furthermore, the loop below (which plots the contents of ppicData) is executed regardless of the condition since an else is missing; hence this one pixel gets overwritten.

Game Boy Advanced Home brew image issue in C

1 Answers1