/*

  PONG in AVR assembly

  ┍━━━━━━━━━━━━━━━━━━━━━━━━━━━━┑
  │	Write your code in pong.S  │
  ┕━━━━━━━━━━━━━━━━━━━━━━━━━━━━┙

  Keep this file empty!

*/

avr-pong.ino

Build a PONG game in AVR Assembly.

See [the Hackaday Project Page] for instructions.


README.md

diagram.json

; Write your code in this file
; Charl
.global main
.global __do_copy_data

.data
  frame:  .byte 0b11111000, 0b10101010, 0x0f,0,0,0,0,0,0,0,0,0,0,0,0,0
          .space 128
  frame_height: .byte 8
  paddle_1_pos: .byte 4
  paddle_2_pos: .byte 6
  button_pressed: .byte 0
  frame_time: .byte 255 ; ms to wait frame after update calls
  ball_x: .byte 8
  ball_y: .byte 4


.text

main:
  call setup
  call setup_spi
  call loop
ret

loop:
  call clear_frame_buffer
  call update_game_state
  call update_frame
  call draw_frame  
  call delay_frame
  jmp loop
ret

delay_frame:
  lds r24, frame_time
  1:
  ldi r26, 4000 & 0xff
  ldi r27, 4000 >> 8

  2:
  sbiw r26, 1
  brne 2b

  sbiw r24, 1
  brne 1b
ret

setup:
  ;set DDRD to input
  ldi r18, 0x00
  out 0x0a, r18

  ldi r18,0xff
  out 0x0b, r18
ret

setup_spi:
  ; set spi pinmodes
  ldi r24, 0b00101100
  out 0x04, r24
  ; set spi master mode
  ldi r24, 0b01010001
  out 0x2c, r24
ret

transmit_data:
  ;ldi r24, 0x03
  out 0x2e, r24

  wait_for_transmit:
    in r24, 0x2d
    andi r24, 0b10000000
    subi r24, 0b10000000
    breq done_waiting
    jmp wait_for_transmit
    done_waiting:
ret

chip_select:
  ldi r24, 0b00000000
  out 0x03, r24
ret

chip_deselect:
  ldi r24, 0b00000100
  out 0x03, r24
ret

update_frame:
  ;draw paddles
  lds r23, paddle_1_pos
  push r23
  ldi r24, 0
  ldi r22, 1
  call set_pixel

  pop r23
  push r23
  subi r23, 1
  ldi r24, 0
  ldi r22, 1
  call set_pixel

  pop r23
  subi r23, -1
  ldi r24, 0
  ldi r22, 1
  call set_pixel

  ;draw ball
  lds r24, ball_x
  lds r23, ball_y
  ldi r22, 1
  call set_pixel

ret

update_game_state:
  lds r17, button_pressed

  in r18, 0x09
  andi r18, 0xff

  cpi r18, 0b10111111
  brne 1f
    cpi r17, 1
    breq 1f

      call move_paddle_down

      ldi r17,1

      ldi r26, lo8(button_pressed)
      ldi r27, hi8(button_pressed)
      st x, r17
  1:
  cpi r18, 0b01111111
  brne 2f
    cpi r17, 1
    breq 2f

      call move_paddle_up

      ldi r17,1

      ldi r26, lo8(button_pressed)
      ldi r27, hi8(button_pressed)
      st x, r17
  2:

  cpi r18, 0b11111111
  brne 3f
      ldi r17, 0
      ldi r26, lo8(button_pressed)
      ldi r27, hi8(button_pressed)
      st x, r17
  3:

  call  move_ball

ret

move_paddle_down:
  ldi r26, lo8(paddle_1_pos)
  ldi r27, hi8(paddle_1_pos)
  lds r16, paddle_1_pos
  subi r16, -1
  cpi r16, 6
  brsh 2f
  st x, r16
  jmp 3f
  2:
  ldi r16, 6
  st x, r16
  3:
ret

move_paddle_up:
  ldi r26, lo8(paddle_1_pos)
  ldi r27, hi8(paddle_1_pos)
  lds r16, paddle_1_pos
  subi r16, 1
  cpi r16, 2
  brlo 2f
  st x, r16
  jmp 3f
  2:
  ldi r16, 1
  st x, r16
  3:
ret

move_ball:
  ldi r26, lo8(ball_x)
  ldi r27, hi8(ball_x)

  lds r17, ball_x
  subi r17, -1
  st x, r17
  
ret

draw_frame:
  ;;oad frame location
  ldi r26, lo8(frame)
  ldi r27, hi8(frame)
  lds r17, frame_height
  ldi r18, 1

  1:  
  call chip_select
  
  ;load and transmit row number, segment 1
  mov r24, r18
  call transmit_data

  ;load and transmit column data, segment 1
  ld r24, X+
  call reverse_bits
  call transmit_data

  ;load and transmit row number, segment 2
  mov r24, r18
  call transmit_data

  ;load and transmit column data, segment 2
  ld r24, X+
  call reverse_bits
  call transmit_data

  call chip_deselect


  cp r17, r18
  inc r18  
  brne 1b
  
ret

clear_frame_buffer:
  ldi r26, lo8(frame)
  ldi r27, hi8(frame)
  lds r17, frame_height

  ldi r18, 0
  ldi r19, 0x00
  
  1:
  st X+, r19
  st X+, r19

  inc r18
  cp r17, r18

  brne 1b
ret

reverse_bits:
  swap r24
  mov r23, r24
  andi r23, 0xcc
  lsr r23
  lsr r23

  mov r22, r24
  andi r22, 0x33
  lsl r22
  lsl r22
  or r22, r23
  mov r24, r22

  mov r23, r24
  andi r23, 0xaa
  lsr r23

  mov r22, r24
  andi r22, 0x55
  lsl r22
  or r22, r23
  mov r24, r22
ret

;r24: X, r23 :Y coords, r22: on/off
set_pixel:
  ;load frame location
  ldi r26, lo8(frame)
  ldi r27, hi8(frame)

  ;select row from frame
  ldi r20, 2
  mul r23, r20
  mov r23, r0

  inc r23

  ldi r19, 0
  add r26, r23
  adc r27, r19

  ldi r21, 0x80

  mov r20, r24
  andi r20, 0b00000111
  jmp 2f

  3:
  lsr r21  
  dec r20
  2:
  brne 3b

  sbrs r24, 3
  ld r16, -x  
  ld r16, x

  or r16, r21
  sbrs r22, 0
  eor r16, r21

  ;sbrs r24, 3  
  ;st -x, r16
  st x, r16  
  
ret



