How to mirror an array with WS2801 LEDs? - arrays

Question

I have the following code http://pastebin.com/25ugwNhK# which basically reads the equalizer color values for 7 differenece frequencies and maps them to a color. Then mirrors them projected on a string starting from both ends.
void EQcenterBarString(){
// reads eq and plugs RGB values directly into each consecutive pixel, mirrored from center.
if(LoopCnt <= PixelCount) {
readEQ();
//Add new color to array at pointer position
//For Array replace LoopCnt with row number
leds[LoopCnt].r = ledRed;
leds[LoopCnt].g = ledGreen;
leds[LoopCnt].b = ledBlue;
//now the opposite
//For Array replace Pixel - Loop with ROWS - row number
leds[PixelCount - LoopCnt].r = ledRed;
leds[PixelCount - LoopCnt].g = ledGreen;
leds[PixelCount - LoopCnt].b = ledBlue;
FastSPI_LED.show();
LoopCnt++;
}else{LoopCnt=0;}
}
I'd like to make this be able to work with an Array of [ROWS] [COLS], however I'm struck with getting the pixels to update or loop through the array.
My pseudo code looks something like this:
void EQcenterBarArray(){
int pixel = 0, rows = 0, cols = 0;
//rows = 0, loop through till the end going down the array, rows++
for(rows = 0; rows < ROWS; rows++) {
readEQ();
// should light up a whole row at once starting from the beginning of the array
while (cols != COLS) { //while in row # x fill all the col values until = COL value
pixel = ( LEDmatrix[rows][cols] ); // set pixel index to the array pos
leds[pixel].r = ledRed;
leds[pixel].g = ledGreen;
leds[pixel].b = ledBlue;
FastSPI_LED.show(); //update the pixel and move to next col value
cols++; //should fill whole col on row x ?
}
//now the opposite side
// should light up a whole row at once starting from the end of the array
while (cols != COLS) {
pixel = ( LEDmatrix[(ROWS-1) - rows][cols] ); //take the total# of ROWS and subtract the current row value to create a mirror effect?
leds[pixel].r = ledRed;
leds[pixel].g = ledGreen;
leds[pixel].b = ledBlue;
FastSPI_LED.show();
cols++;
}
}
}
However, when I run this through my arduino with WS2801 lights using the FastSPI_LED library I only get one row to light up and it doesn't cycle through all the rows?

Answer 1

You need to reset cols to 0 at the start of each iteration of your rows for() loop.
for(rows = 0; rows < ROWS; rows++) {
readEQ();
// should light up a whole row at once starting from the beginning of the array
cols = 0; //reset cols to zero to iterate next set of columns
while (cols != COLS) { //while in row # x fill all the col values until = COL value
Incidentally, it's not clear if you should call readEQ every row, or only after you have finished an entire display grid - each will have various advantages (rate of partial response, vs self-consistency of updates)