Update PIO 1bpp encode

software/apps/moon/main.c

@@ -78,7 +78,7 @@ int main() {
 	dma_channel_configure(dma_chan_get, &c,
 		NULL,
 		&encode_pio->rxf[encode_sm],
-		FRAME_WIDTH,
+		FRAME_WIDTH / DVI_SYMBOLS_PER_WORD,
 		false
 	);
 #endif

software/libdvi/tmds_encode_1bpp.pio

@@ -1,45 +1,46 @@
 .program tmds_encode_1bpp
 
-; 1bpp black/white pixels go in, TMDS symbols come out
-; y is initialised to 0x60005555
-; Autopull enabled, threshold 32
-; Autopush enabled, threshold 16
+; 1bpp black/white pixels go in, TMDS symbols come out.
+; Each output word contains two output symbols, each 10 bits in size,
+; right-justified. The least-significant symbol is displayed first.
+;
+; We can encode using the following LUT: (yes this is compliant)
+;
+; x % 2 | colour | symbol
+; ------+--------+-------
+; 0     | 0      | 0x100
+; 0     | 1      | 0x200
+; 1     | 0      | 0x1ff
+; 1     | 1      | 0x2ff
+;
+; OSR: shift to right, autopull, threshold 32
+; ISR: shift to right, autopush, threshold 24
+;
+; Note the ISR needs to be shifted to *right* so that we can get the first
+; pixel in the less-significant position. Threshold 24 so we can get 8x 0-bits
+; at the LSBs for free :)
 
-; x == 0 -> first branch nontaken, second taken
-; x == 1 -> first branch taken, second nontaken
 even_pixel:
     out x, 1
-    jmp x--, skip1
-    mov y, !y
-skip1:
-    mov isr, ::y
-    jmp x--, skip2
-    mov y, !y
-skip2:
-    in y, 16
+    mov y, ~x
+    in y, 1
+    in x, 1
 
 odd_pixel:
+    mov x, ~null
+    in x, 8
     out x, 1
-    jmp x--, skip3
-    mov isr, ::y
-skip3:
-    mov y, !y
-    jmp x--, skip4
-    mov isr, ::y
-skip4:
-    in y, 16
-
+    mov y, ~x
+    in y, 1
+    in x, 13     ; Bring total shift to 24, triggering push.
 
 % c-sdk {
 static inline void tmds_encode_1bpp_init(PIO pio, uint sm) {
     uint offset = pio_add_program(pio, &tmds_encode_1bpp_program);
     pio_sm_config c = tmds_encode_1bpp_program_get_default_config(offset);
     sm_config_set_out_shift(&c, true, true, 32);
-    sm_config_set_in_shift(&c, false, true, 16);
+    sm_config_set_in_shift(&c, true, true, 24);
     pio_sm_init(pio, sm, offset, &c);
-    pio_sm_put_blocking(pio, sm, 0x60005555u);
-    pio_sm_exec(pio, sm, pio_encode_pull(false, true));
-    pio_sm_exec(pio, sm, pio_encode_out(pio_y, 32));
     pio_sm_set_enabled(pio, sm, true);
 }
 %}