File content as of revision 1:d6cb4e7c1518:

#include "mbed.h"
#include "GD.h"
#include "arduino.h"
#include "shield.h"

GDClass GD(ARD_MOSI, ARD_MISO, ARD_SCK, ARD_D9, USBTX, USBRX) ;
SPI spimain(ARD_MOSI, ARD_MISO, ARD_SCK); // mosi, miso, sclk
#define PI 3.1415926535

void readn(byte *dst, unsigned int addr, int c) {
    GD.__start(addr);
    while (c--)
        *dst++ = spimain.write(0);
    GD.__end();
}

static byte coll[256];
static void load_coll() {
    while (GD.rd(VBLANK) == 0)  // Wait until vblank
        ;
    while (GD.rd(VBLANK) == 1)  // Wait until display
        ;
    while (GD.rd(VBLANK) == 0)  // Wait until vblank
        ;
    readn(coll, COLLISION, sizeof(coll));
}

void setup() {
    int i;

    GD.begin();

    GD.wr(JK_MODE, 1);
    GD.wr16(RAM_PAL, RGB(255,255,255));

    // Use the 4 palettes:
    // 0 pink, for J sprites
    // 1 green, for K sprites
    // 2 dark pink, J collisions
    // 3 dark green, K collisions
    for (i = 0; i < 256; i++) {
        GD.wr16(RAM_SPRPAL + (0 * 512) + (i << 1), RGB(255, 0, 255));
        GD.wr16(RAM_SPRPAL + (1 * 512) + (i << 1), RGB(0, 255, 0));
        GD.wr16(RAM_SPRPAL + (2 * 512) + (i << 1), RGB(100, 0, 100));
        GD.wr16(RAM_SPRPAL + (3 * 512) + (i << 1), RGB(0, 100, 0));
    }
}

byte spr;
static void polar(float th, int r, byte jk) {
    // add 2 to the palette if this sprite is colliding
    byte colliding = coll[spr] != 0xff;
    GD.sprite(spr, 200 + int(r * sin(th)), 142 + int(r * cos(th)), 0, jk + (colliding ? 2 : 0), 0, jk);
    spr++;
}
Timer timer;
int main() {
    
    timer.start();
    setup();
    byte i;
    float th;
    while (1) {
        spr = 0;
        // draw the J sprites (pink)
        for (i = 0; i < 5; i++) {
            th = (((timer.read_us()+2147)/500) / 3000.) + 2 * PI * i / 5;
            polar(th, 134, 0);
        }
        // draw the K sprites (green)
        randomSeed(4);
        for (i = 0; i < 17; i++) {
            th = (((timer.read_us()+2147)/500) / float((rand()%2000)+1000)) + 2 * PI * i / 17;
            polar(th, 134, 1);
        }
        load_coll();
    }
}