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Merged
mkalkbrenner merged 5 commits into from
Nov 5, 2025
Merged

Data East / Sega fixing #7

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1b7b87b
Take basics of whitestar, use previously done framedetect
PastorL69 Nov 5, 2025
025ea57
remove rclk because unused, fix other irq
PastorL69 Nov 5, 2025
4ca1703
Adjust DE-Sega values to reflect whitestar as it's the same frame con…
PastorL69 Nov 5, 2025
76ef9b9
comment does not reflect DE/Sega logic
PastorL69 Nov 5, 2025
0af95a2
fixed DE-Sega manufacturer detection
PastorL69 Nov 5, 2025
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55 changes: 17 additions & 38 deletions src/dmd_interface_desega.pio
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Original file line number Diff line number Diff line change
Expand Up @@ -4,66 +4,47 @@
.define COLLAT 4
.define DOTCLK 3
.define SDATA 2
.define FRAME_START 4


.program dmd_reader_desega

; Send using an external clock on the SPI interface

; initialize y with 4096 = number of pixels (128x32)
set x, 1
in x, 1
in null, 13
mov y, isr
; initialize y with 8191, number of pixels ((128 x LSB + 128 x MSB) x 32) - 1 because counting starts at 0.
set x, 31 ; x = 31 (max 5-bit value)
in x, 5 ; shift in 5 bits, isr = 31
set x, 31 ; x = 31
in x, 5 ; shift in 5 bits, isr = 1023
set x, 15 ; x = 15
in x, 3 ; shift in 3 bits, isr = 8191
in null, 3 ; pad with 3 zeros
mov y, isr ; y = 8191

.wrap_target

mov x, y ; load number of pixels
mov isr, null ; reset shift counter

irq clear 4
wait irq 4
irq clear FRAME_START
wait irq FRAME_START


; this is the loop for the most significant bit
dotloop1:
dotloop:
wait 0 gpio DOTCLK ; falling edge
wait 1 gpio DOTCLK ; raising edge
in pins 1 ; read pin data
in null 1 ; right padding
jmp x-- dotloop1

mov x, y ; load number of pixels
mov isr, null ; reset shift counter

; There's an empty line between LSB and HSB plane
wait 0 gpio RCLK
wait 1 gpio RCLK

; this is the loop for the least significant bit
; in this loop, the bit value is multipled by 2 by shifting it one bit
dotloop2:
wait 0 gpio DOTCLK ; falling edge
wait 1 gpio DOTCLK ; raising edge
in null 1 ; left padding
wait 1 gpio DOTCLK ; raising edge
in pins 1 ; read pin data
jmp x-- dotloop2

jmp x-- dotloop

.wrap


.program dmd_framedetect_desega

.wrap_target

; Data East/Sega frame start detection
; ~7.86µs is the longest state in which DE can be low without it being a new frame
; Each nop [31] = 32 cycles = 256 ns @125 MHz
; We go with 10 µs to be safe and confirm the start of a new frame, which is 256ns * 39 = 9.98 µs

wait_low:
wait 0 gpio DE ; Wait for DE to go low

set x, 20 ; Use x as storage for 20 iterations

delay_loop:
Expand All @@ -73,7 +54,7 @@ delay_loop:

; After ~10 µs, check if still low
jmp pin, wait_low ; If pin went high early → back to wait_low
irq 4 ; Pin remained low long enough → trigger IRQ
irq FRAME_START ; Pin remained low long enough → frame started

wait 1 gpio DE ; Wait again for it to go high before restarting cycle
jmp wait_low ; went high, time to go back to wait_low
Expand All @@ -89,11 +70,9 @@ static inline void dmd_reader_desega_program_init(PIO pio, uint sm, uint offset)
sm_config_set_in_pins(&c, 2); // SDATA

// Set the pin direction at the PIO
pio_sm_set_consecutive_pindirs(pio, sm, 5, 1, false); // RCLK
pio_sm_set_consecutive_pindirs(pio, sm, 2, 2, false); // SDATA, DOTCLK

// Connect these GPIOs to this PIO block
pio_gpio_init(pio, 5); // RCLK
pio_gpio_init(pio, 3); // DOTCLK
pio_gpio_init(pio, 2); // SDATA

Expand Down
13 changes: 7 additions & 6 deletions src/dmd_reader.c
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Original file line number Diff line number Diff line change
Expand Up @@ -376,8 +376,8 @@ int detect_dmd() {
spi_notify_onoff(DMD_SAM);
return DMD_SAM;

} else if ((dotclk > 640000) && (dotclk < 700000) && (de > 5000) &&
(de < 5300) && (rdata > 3800) && (rdata < 4000)) {
} else if ((dotclk > 600000) && (dotclk < 680000) && (de > 4800) &&
(de < 5200) && (rdata > 2500) && (rdata < 2650)) {
printf("Data East/Sega detected\n");
spi_notify_onoff(DMD_DESEGA);
return DMD_DESEGA;
Expand Down Expand Up @@ -650,12 +650,13 @@ bool init() {

lcd_width = 128;
lcd_height = 32;
lcd_bitsperpixel = 2; // Data East/ Sega is 2bpp
lcd_bitsperpixel = 2; // DE-Sega is 2bpp
lcd_pixelsperbyte = 8 / lcd_bitsperpixel;
lcd_planesperframe = 2; // in DE/Sega, there's a MSB and a LSB plane
lcd_planesperframe = 1; // in DE-Sega, there's only one plane, containg
// one LSB row followed by one MSB row and so on
lcd_lineoversampling =
LINEOVERSAMPLING_2X; // in DE/Sega each line is sent twice
lcd_mergeplanes = MERGEPLANES_ADDSHIFT; // required for correct 2bpp merge
LINEOVERSAMPLING_2X; // in DE-Sega each line is sent twice
lcd_mergeplanes = MERGEPLANES_NONE; // required for correct 2bpp merge
} else {
printf("Unknown DMD type, aborting\n");
return false;
Expand Down