Display lists vs direct drawing?

[Malban]

Following code works (in Vide):

#include <vectrex.h>

static void cstrcpy(char *dest, char *src) {
 char c; do { c = *src++; *dest++ = c; } while (c != '\0');
}

static char DEMO[15];

static void cMoveto_d(signed int y, signed int x)
{
dp_VIA_port_a = y;         // y pos to dac
dp_VIA_cntl = 0xce;    // disable zero, disable all blank
dp_VIA_port_b = 0;         // mux enable, dac to -> integrator y (and x)
dp_VIA_shift_reg = 0;      // all output is BLANK
dp_VIA_port_b++;           // mux disable, dac only to x
dp_VIA_port_a = x;         // dac -> x
dp_VIA_t1_cnt_hi=0;        // start timer
while ((dp_VIA_int_flags & 0x40) == 0); // wait till timer finishes
}

__attribute__((interrupt)) static void  draw_graphics(void)
{
 if ((dp_VIA_int_flags & 0x20) == 0) {
   // for anything except the t2 timer we want to rti immediately.
   return;
 }

 Vec_Loop_Count++;

 dp_VIA_t2 = Vec_Rfrsh;
 dp_VIA_t1_cnt_lo= (unsigned int)255;
 cMoveto_d(127,127);
 dp_VIA_cntl = 0xcc; // enable zero, enable all blank
 cMoveto_d(-128,-128);
 dp_VIA_cntl = 0xcc; // enable zero, enable all blank

 dp_VIA_port_a = 0; // dac = 0
 dp_VIA_port_b = 3; // mux=1, disable mux
 dp_VIA_port_b = 2; // mux=1, enable mux
 dp_VIA_port_b = 2; // delay
 dp_VIA_port_b = 1; // disable mux

 // graphics executed here.  Small placeholder for now:
 Print_Str_d(0, -70, DEMO);
<span style="font-family: Verdana, Arial; font-size: 10pt;">}</span>

#define IRQBASE 0xCBF8 // this must be IRQ not FIRQ!
unsigned long volatile * const IRQ = (unsigned long *) (IRQBASE+1);
unsigned int volatile * const IRQ_INST = (unsigned int *) IRQBASE;

int main(void)
{
   char *p;
   *IRQ_INST = (unsigned int)0x7e; // JMP ... this is actually code!, first a JMP instruction
   *IRQ = (unsigned long)&draw_graphics; // to Address
   cstrcpy(DEMO, "HELLO 0000000\x80"); // long enough to allow freewheeling counter...
   p = DEMO+12;

   // ENABLE INTERRUPTS HERE! (How???)

 // ensure timer is sensible to start with
 dp_VIA_t2 = Vec_Rfrsh;
 
 dp_VIA_int_enable |= 0x20;
 asm("andcc #0xef"); // enable IRQ with 6809



for (;;) {
        while (*p == '9') { // find digit to increment - X9999 becomes (X+1)0000
          *p = '0';
          p -= 1;
          if (*p == ' ') {
             cstrcpy(DEMO, "HELLO 0000000\x80");
             p = DEMO+12;
          }
        }
        *p += 1;
        p = DEMO+12;
        // Print_Str_d(0, -70, DEMO);
        // Only display once every 1/50s in interrupt routine
}

return 1; // cold reset - NOT REACHED
}



[gtoal]

Hah! You beat me to it! I just got this working tonight... (hadn't seen your post until just now)

gtoal.com/vectrex/interrupter/main.c.html

#include <vectrex.h>

static void cstrcpy(char *dest, char *src) {
  char c; do { c = *src++; *dest++ = c; } while (c != '\0');
}

static char DEMO[15];

static void cMoveto_d(signed int y, signed int x)
{
  dp_VIA_port_a = y; // y pos to dac
  dp_VIA_cntl = 0xce; // disable zero, disable all blank
  dp_VIA_port_b = 0; // mux enable, dac to -> integrator y (and x)
  dp_VIA_shift_reg = 0; // all output is BLANK
  dp_VIA_port_b++; // mux disable, dac only to x
  dp_VIA_port_a = x; // dac -> x
  dp_VIA_t1_cnt_hi=0; // start timer
  while ((dp_VIA_int_flags & 0x40) == 0); // wait till timer finishes
}

static void draw_graphics(void)
{
  if ((dp_VIA_int_flags & 0x20) == 0) {
    // for anything except the t2 timer we want to rti immediately.
    asm("rti");
  }

  Vec_Loop_Count++;

  dp_VIA_t2 = Vec_Rfrsh;
  dp_VIA_t1_cnt_lo= (unsigned int)255;
  cMoveto_d(127,127);
  dp_VIA_cntl = 0xcc; // enable zero, enable all blank
  cMoveto_d(-128,-128);
  dp_VIA_cntl = 0xcc; // enable zero, enable all blank

  dp_VIA_port_a = 0; // dac = 0
  dp_VIA_port_b = 3; // mux=1, disable mux
  dp_VIA_port_b = 2; // mux=1, enable mux
  dp_VIA_port_b = 2; // delay
  dp_VIA_port_b = 1; // disable mux

  // graphics executed here. Small placeholder for now:
  Intensity_5F();
  Print_Str_d(0, -70, DEMO);

  // return to user code
  asm("rti");
}

int main(void)
{
  char *p;

  // CBF8 is where the hard-coded interrupt vector causes control to jump
  // to on IRQ, so we need to plant "JMP draw_graphics" at that address rather
  // than just the address of "draw_graphics"...
  // CBF8: 7E HI LO
  p = (char *)0xCBF8; *p++ = (char)0x7E;
  *p++ = (char)(((long)&draw_graphics) >> 8L);
  *p++ = (char)(((long)&draw_graphics) & 255L);

  cstrcpy(DEMO, "HELLO 0000000\x80"); // long enough to allow freewheeling counter...
  p = DEMO+12;

  // ENABLE INTERRUPTS HERE!
  dp_VIA_int_enable |= 0x20; // this tells the VIA to enable interrupts
  // This enables the CPU to handle interrupts:
  asm(" pshs cc");
  asm(" puls a");
  asm(" anda #239"); // Clear I bit ... 0x10 ... 16 - 255-16=239
  asm(" pshs a");
  asm(" puls cc");

  for ( ; ; ) {
    while (*p == '9') { // find digit to increment - X9999 becomes (X+1)0000
      *p = '0';
      p -= 1;
      if (*p == ' ') {
        cstrcpy(DEMO, "HELLO 0000000\x80");
        p = DEMO+12;
      }
    }
    *p += 1;
    p = DEMO+12;
    // Print_Str_d(0, -70, DEMO);
    // Only display once every 1/50s in interrupt routine
  }

  return 1; // cold reset - NOT REACHED
}

[gtoal]

Well, guys, I'm quite pleased with the way this is going... I have a program now that puts up some text, some fixed graphics, and 12 animated sprites. This is more than can be done in 1/50s the normal way (*) but with interrupt-driven graphics, the display remains solid - however the code that moves the sprites is not invoked as frequently - it's doing about 10 position updates per second. To keep an animation moving at the desired speed, this could could move objects by 5 positions instead of 1 each cycle.

If the amount of graphics displayed is so high that there's no time left to do the move computations, the picture freezes...

gtoal.com/vectrex/interrupter/main.c.html

(*: normal Bios-like way - I'm not comparing this to the super fast drawing done by expert coders like Malban and Thomas)

G

[gtoal]

There were two items we discussed in this thread - a graphics library that was separated from the actual drawing, and the background interrupt handling to implement it. The latter has been covered by Malban in another thread, but we haven't discussed the graphics lib part of this since the initial post. It occurred to me today that I haven't yet posted anything about the work I've been doing in that direction. A couple of months ago this is how far I had got: gtoal.com/vectrex/SpriteLib/ - note that it is just a 'work in progress' experiment, I don't think it's ready for prime time, but you can see from it which ideas might work and which are too expensive as Malban predicted earlier. But from the experiment, I think that something worthwhile is possible if, so far, only for beginner programmers who are not pushing the envelope. (This draft doesn't yet implement the interrupt-driven background drawing, this was just a try at defining an interface).