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58c629753c
videochargen/main.S

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ArmAsm
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first commit vertical line at about 1/3 of the horizontal line
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#include <avr/io.h>
#include "macro.h"
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#include "const.h"
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.data
image:
.byte 0xff
show_image:
.byte 0x00
button_next_image:
.byte 0x0
current_jump_table:
.word 0x0
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.text
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.global main
main:
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ldi r16, 0x30 ; port B, pin 4 and 5 as output, others as input
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sts DDRB, r16
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; set interrupt vectors at address 0x0, not bootloader
; timing is important, see atmel datasheet
ldi r16, (1 << IVCE)
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ldi r17, 0
out IO(MCUCR), r16
out IO(MCUCR), r17
"diagonal line" not the whole screen, but vertically locked actually it has some issues, there is a single dot (at the end/beginning of a cycle) that messes up the horizontal sync and moves all the picture... must be fixed
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ldi r16, 0xa ; external interrupt 0 and 1, falling edge
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sts EICRA, r16
"diagonal line" not the whole screen, but vertically locked actually it has some issues, there is a single dot (at the end/beginning of a cycle) that messes up the horizontal sync and moves all the picture... must be fixed
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ldi r16, 0x3 ; external interrupt 0 and 1, mask enable
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sts EIMSK, r16
semi working timer for skipping back porch
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ldi r16, 0x02 ; don't connect output pins to timer, CTC[1:0] mode
sts TCCR0A, r16
using a prescaler (eg /64) may lead to horizontal offset errors because 1cycle off actually means many cycles off (eg 64)
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ldi r16, 0x01 ; CTC[2] mode, no prescaler
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sts TCCR0B, r16
; init variables
ldi r16, 0
sts frame, r16
sts frame + 1, r16
sts line, r16
avoid bouncing when starting/resetting
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ldi r16, 0xfe
sts line + 1, r16
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ldi r16, 0xff
sts image, r16
ldi r16, 0
sts show_image, r16
semi working timer for skipping back porch
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hardwired jump table This makes the microcontroller very application dependent, but may save use some headaches. The idea is to write a program to produce the code to show a complex drawing.
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; r0 always holds 0
clr r0
line buffer dynamic update
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call setup_c
introduced line buffer of 160 pixel
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sei ; global interrupt enable
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1:
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rjmp 1b
"diagonal line" not the whole screen, but vertically locked actually it has some issues, there is a single dot (at the end/beginning of a cycle) that messes up the horizontal sync and moves all the picture... must be fixed
2021-06-26 21:42:23 +00:00
.global int_horizontal_sync
back porch skipping, wasting clock cycles, basically
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int_horizontal_sync: ; +3
push r31 ; +5
in r31, IO(SREG) ; +6, status register
push r31 ; +8
push r30 ; +10
line, frame as words (16 bit)
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; if (line >= VERTICAL_OFFSET), then enter
back porch skipping, wasting clock cycles, basically
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lds r30, line ; +12
lds r31, line + 1 ; +14
adiw z, 1 ; +16
sts line, r30 ; +18
sts line + 1, r31 ; +20
cpi r31, 0 ; +21
hardwired jump table This makes the microcontroller very application dependent, but may save use some headaches. The idea is to write a program to produce the code to show a complex drawing.
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breq enter ; +23
jmp int_horizontal_sync_end
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vertical line, scrolling from left to right sufficiently handles the back/front porch without disrupting the sync signal todo improvement: compute a sensible amount of cycles to waste during the porch
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enter:
back porch skipping, wasting clock cycles, basically
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; here, +23 or +24 cycles have passed since horizontal sync
; so, there are still ~168 cycles before first useful data
semi working timer for skipping back porch
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ldi r31, 0
sts TCNT0, r31
ldi r31, HORIZONTAL_OFFSET ; set counter TOP
sts OCR0A, r31
ldi r31, 0x7 ; clear any pending interrupt
sts TIFR0, r31
vertical line, scrolling from left to right sufficiently handles the back/front porch without disrupting the sync signal todo improvement: compute a sensible amount of cycles to waste during the porch
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semi working timer for skipping back porch
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lds r31, TIMSK0
ori r31, 0x02 ; mask enable interrupt timer A
sts TIMSK0, r31
int_horizontal_sync_end:
pop r30
pop r31
out IO(SREG), r31
pop r31
reti
.global int_timer_0
int_timer_0:
; here we are at the beginning of the visible line
push r31
in r31, IO(SREG)
push r31
introduced line buffer of 160 pixel
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push r30
push r29
semi working timer for skipping back porch
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; turn off interrupt
lds r31, TIMSK0
andi r31, 0xfd ; mask disable interrupt timer A
sts TIMSK0, r31
multiple frames
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lds r31, show_image
cpi r31, 0x1
brne jump_table_return_address
lds zl, current_jump_table
lds zh, current_jump_table + 1
; ldi zl, pm_lo8(line_jump_table_0)
; ldi zh, pm_hi8(line_jump_table_0)
vertical line, scrolling from left to right sufficiently handles the back/front porch without disrupting the sync signal todo improvement: compute a sensible amount of cycles to waste during the porch
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multiple frames
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clr r0
hardwired jump table This makes the microcontroller very application dependent, but may save use some headaches. The idea is to write a program to produce the code to show a complex drawing.
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lds r29, line
add zl, r29
adc zh, r0
add zl, r29
adc zh, r0
ijmp
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generates an hardwired test pattern This does not work as expected, and I don't understand why. Clock cycle count seems ok, but if there are no changes in the pixels, it seems to go faster
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.global jump_table_return_address
hardwired jump table This makes the microcontroller very application dependent, but may save use some headaches. The idea is to write a program to produce the code to show a complex drawing.
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jump_table_return_address:
introduced line buffer of 160 pixel
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pop r29
pop r30
"diagonal line" not vertically locked, just a test also not the whole screen, just a bit
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pop r31
out IO(SREG), r31
pop r31
reti
first commit vertical line at about 1/3 of the horizontal line
2021-06-26 17:15:17 +00:00
"diagonal line" not the whole screen, but vertically locked actually it has some issues, there is a single dot (at the end/beginning of a cycle) that messes up the horizontal sync and moves all the picture... must be fixed
2021-06-26 21:42:23 +00:00
.global int_vertical_sync
int_vertical_sync:
push r31
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in r31, IO(SREG)
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push zl
push zh
push yl
push yh
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line, frame as words (16 bit)
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lds r31, frame + 1
lds r30, frame
adiw z, 1
sts frame + 1, r31
sts frame, r30
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line, frame as words (16 bit)
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ldi r30, 1
ldi r31, 0
sts line, r30
sts line + 1, r31
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multiple frames
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; check button
in r31, IO(PINB)
andi r31, 0x08
breq check_if_released
ldi r31, 1
sts button_next_image, r31
jmp int_vertical_sync_end
check_if_released:
lds r31, button_next_image
cpi r31, 1
brne int_vertical_sync_end
; here button is released
implemented transition mode if transition_mode pin is high, then images are shown continuosly (eg the next image is shown as soon as the next_image button is pressed) but if transition_mode pin is low, then, when you press the button, the current image disappears, and the next one appears when you press the button again
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; read transition mode
in r31, IO(PINB)
andi r31, 0x04
; if transition mode == 1, then always show image
; TODO an huge shitty spaghetti code
breq 1f
ldi r31, 0
sts show_image, r31
1:
multiple frames
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lds r31, show_image
cpi r31, 1
breq 1f
ldi r31, 1
sts show_image, r31
rjmp 2f
1:
ldi r31, 0
sts show_image, r31
rjmp end_button_release
2:
; show image
ldi zl, pm_lo8(line_jump_table_0)
ldi zh, pm_hi8(line_jump_table_0)
clr yl
lds yh, image
inc yh
sts image, yh
add zh, yh
add zh, yh
sts current_jump_table, zl
sts current_jump_table + 1, zh
ldi r31, 0x01
sts show_image, r31
end_button_release:
clr yl
sts button_next_image, yl
something strange is happening
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int_vertical_sync_end:
multiple frames
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pop yh
pop yl
pop zh
pop zl
something strange is happening
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out IO(SREG), r31
"diagonal line" not the whole screen, but vertically locked actually it has some issues, there is a single dot (at the end/beginning of a cycle) that messes up the horizontal sync and moves all the picture... must be fixed
2021-06-26 21:42:23 +00:00
pop r31
reti
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