git.defcon.no Git - avrfbosd/blob - syncgen/main.c

   1 #include <avr/io.h>
   2 #include <avr/interrupt.h>
   3 #include <util/delay.h>
   4 #define ZERO  PORTB=0b000
   5 #define BLACK PORTB=0b001
   6
   7 //       -----..-----   ^
   8 //      |            |  |
   9 //     -| RST    VCC |-`
  10 //      |            |
  11 //   .--| X1     PB2 |-
  12 //  [ ] |            |  470R
  13 //   '--| X2     PB1 |--^v^v-.
  14 //      |            |       |----> VidOut
  15 //   .--| GND    PB0 |--^v^v-'
  16 //   |  |            |  1kR
  17 //-----  ------------
  18
  19 #include "avrosdlogo.h"
  20
  21 volatile int rasterline;
  22 volatile uint16_t line;
  23
  24 volatile uint8_t hres;
  25 volatile int renderLine;
  26 int stretch;
  27
  28 void asm_render_line( void ) {
  29         __asm__ __volatile__ (
  30         ".macro outbit p"               "\n\t"
  31                 "BST    __tmp_reg__,7"  "\n\t"  // Store bit 7 to T
  32                 "BLD    r16,1"          "\n\t"  // Load bit T into r16 bit number 4
  33                 "OUT    \\p,r16"        "\n\t"  // Send contents of r16 to %[port]
  34                 "NOP"                   "\n\t"
  35         ".endm"                         "\n\t"
  36
  37                 "ADD    r26,r28"        "\n\t"  // Add register Y to register X, low part
  38                 "ADC    r27,r29"        "\n\t"  // Add high Y to X with carry from low part
  39
  40                 "IN     r16,%[port]"    "\n\t"  // Save port content to register 16
  41                 "RJMP   start_line"     "\n\t"
  42
  43         "loop_byte:"                    "\n\t"  // Notice that in the macro we always use bit 7 and left-shift
  44                 "BST    __tmp_reg__,6"  "\n\t"  // Here we use bit 6 without left-shift to output bit 0
  45                 "BLD    r16,1"          "\n\t"  // of each byte (except the last bit on the line)
  46                 "OUT    %[port],r16"    "\n\t"  // We do not have time for a left-shift, teh "extra cycle" was used for "dec-branch"
  47                 "NOP"                   "\n\t"
  48
  49         "start_line:"                   "\n\t"
  50                 "LD     __tmp_reg__,X+" "\n\t"  // Load from address pointed to by X into temporary register, then increment X-pointer
  51
  52                 "outbit %[port]"        "\n\t"  // Output bit 7 using Macro
  53                 "LSL    __tmp_reg__"    "\n\t"  // Left-shift for next bit
  54                 "outbit %[port]"        "\n\t"  // Output bit 6 using Macro
  55                 "LSL    __tmp_reg__"    "\n\t"  // Left-shift for next bit
  56                 "outbit %[port]"        "\n\t"  // Output bit 5 using Macro
  57                 "LSL    __tmp_reg__"    "\n\t"  // Left-shift for next bit
  58                 "outbit %[port]"        "\n\t"  // Output bit 4 using Macro
  59                 "LSL    __tmp_reg__"    "\n\t"  // Left-shift for next bit
  60                 "outbit %[port]"        "\n\t"  // Output bit 3 using Macro
  61                 "LSL    __tmp_reg__"    "\n\t"  // Left-shift for next bit
  62                 "outbit %[port]"        "\n\t"  // Output bit 2 using Macro
  63                 "LSL    __tmp_reg__"    "\n\t"  // Left-shift for next bit
  64                 "outbit %[port]"        "\n\t"  // Output bit 1 using Macro
  65
  66                 "DEC    %[hres]"        "\n\t"  // Decrement num-bytes-remaining-in-resolution
  67                 "BRNE   loop_byte"      "\n\t"  // Branch to loop6 if %[hres] != zero
  68
  69                 "LSL    __tmp_reg__"    "\n\t"  // Left-shift for last bit on the line
  70                 "outbit %[port]"        "\n\t"  // Output bit 0 using Macro.
  71
  72                 "CBI    %[port],1"      "\n\t"  // Clear our "display bit" to ensure we end on black
  73
  74                 :
  75                 : [port] "i" (_SFR_IO_ADDR(PORTB)),
  76                 "x" (testimg_data),
  77                 "y" (renderLine),
  78                 [hres] "d" (hres)
  79         );
  80 }
  81
  82 void hsync(void)
  83 {
  84         line++;
  85         ZERO; _delay_us(4); // sync
  86         BLACK; _delay_us(8);  // Back porch
  87 }
  88
  89 void vsync(uint8_t odd_even)
  90 {
  91         uint8_t a,b;
  92         cli();
  93
  94         // Pre-equalization pulses
  95         b = odd_even ? 6 : 5;
  96         for(a=0; a<b ; a++) // 6x short sync
  97         {
  98                 ZERO;
  99                 _delay_us(2);
 100
 101                 BLACK;
 102                 _delay_us(30);
 103
 104         }
 105
 106         // VSYNC
 107         for(a=0; a<5 ; a++) // 5x long sync
 108         {
 109
 110                 ZERO;
 111                 _delay_us(30);
 112
 113                 BLACK;
 114                 _delay_us(2);
 115
 116         }
 117
 118         // Post-equalization pulses
 119         b = odd_even ? 5 : 4;
 120         for(a=0; a<b ; a++) // 5x short sync
 121         {
 122                 ZERO;
 123                 _delay_us(2);
 124
 125                 BLACK;
 126                 _delay_us(30);
 127
 128         }
 129         line = odd_even ? 5 : 317;
 130         renderLine = 0;
 131
 132         sei();
 133 }
 134
 135 ISR (TIMER0_COMPA_vect)
 136 {
 137         if(line == 310) vsync(0);
 138         else if(line == 622) vsync(1);
 139         else
 140         {
 141                 hsync();
 142                 int t_line = line;
 143                 t_line = ( line > 312 ) ? line - 312 : line;
 144
 145                 if ( t_line > 118 && t_line < 118 + (2*testimg_height) )
 146                 {
 147                         _delay_us(12.3);
 148                         asm_render_line();
 149
 150                         if( !stretch )
 151                         {
 152                                 stretch = 1;
 153                                 renderLine += hres;
 154                                 if ( renderLine > ((testimg_height*hres)-1) ) renderLine = 0;
 155                         } else stretch--;
 156                 }
 157         }
 158         return;
 159 }
 160
 161 int main(void)
 162 {
 163         rasterline = 0;
 164         line = 0;
 165
 166         hres = testimg_width / 8;
 167
 168         DDRB =0b111;
 169
 170         TCCR0A |= (1<<WGM01)|(0<<WGM00);
 171         TCCR0B |= (0<<WGM02)|(0<<CS02)|(1<<CS01)|(0<<CS00);
 172         TIMSK |= (1<<OCIE0A);
 173         OCR0A = 159;
 174
 175         sei();
 176
 177         // Here, we continue to do nothing...
 178         while(1);
 179 }