Fix 128x16 frame orientation

src/dmdreader.cpp

@@ -609,8 +609,10 @@ void dmd_dma_handler() {
   detected_0_1_0_1 = false;
   detected_1_0_0_0 = false;
 
-  // Used for Data East 128x16 to correctly align 64x16 + 64x16
-  int16_t diff = 0;
+  // Used for Data East 128x16 to correctly align 64x16 + 64x16.
+  // Also stores initial data in the hidden part of framebuf.
+  int16_t diff_x16 = 0;
+  uint16_t offset_x16 = 511;
 
   // Fix byte order within the buffer
   uint32_t *planebuf = (uint32_t *)currentPlaneBuffer;
@@ -715,19 +717,18 @@ void dmd_dma_handler() {
           framebuf[out] |= v16;
         }
       } else {  // Data East 128x16 case
-        framebuf[px + diff] = pixval;
+        framebuf[px + diff_x16 + offset_x16] = pixval;
         // increase diff everytime we cross one MSB or LSB row (64 pixels wide)
         // px is based on 4bpp, so we increase every 8 px.
         if ((px & 7) == 7) {
-          diff += 8;
+          diff_x16 += 8;
           // When we have processed half of the pixels in an entire frame,
           // turn the diff into a - value, it will start at the top again and
           // work its way back to 0. This way we prepare framebuf for
           // oversampling
           if (px == ((source_dwordsperplane / 2) - 1)) {
-            diff -=
-                8;  // we immediately decrement once to select the correct row
-            diff *= -1;
+            diff_x16 -= 8;  // immediately decrement once -> select correct row
+            diff_x16 *= -1;
           }
         }
       }
@@ -744,11 +745,12 @@ void dmd_dma_handler() {
   if (dmd_type == DMD_DE_X16_V1 || dmd_type == DMD_DE_X16_V2) {
     // merge the rows and convert from 4bpp to 2bpp with a LUT
     uint32_t *dst, *src1, *src2;
-    dst = src1 = framebuf;
+    dst = framebuf + 64; // start in the middle of 128x32 frame
+    src1 = framebuf + 511; // everything is stored from here onwards
     src2 = src1 + source_dwordsperline;
 
     if (dmd_type == DMD_DE_X16_V1) {
-      for (int l = 0; l < source_height; l++) {
+      for (int l = 0; l < source_height / 2; l++) {
         for (int w = 0; w < source_dwordsperline; w++) {
           uint32_t out = w >> 1;  // Shifting leads to 0, 0, 1, 1, etc
           uint16_t v16 = convert_4bit_to_2bit_de_x16((src1[w] * 3));
@@ -765,7 +767,7 @@ void dmd_dma_handler() {
       }
     } else {
       // DMD_DE_X16_V2 case
-      for (int l = 0; l < source_height; l++) {
+      for (int l = 0; l < source_height / 2; l++) {
         for (int w = 0; w < source_dwordsperline; w++) {
           uint32_t out = w >> 1;  // Shifting leads to 0, 0, 1, 1, etc
           uint16_t v16 = convert_4bit_to_2bit_de_x16((src1[w] + src2[w] * 2));
@@ -1023,7 +1025,7 @@ bool dmdreader_init(bool return_on_no_detection) {
       // we need it to sample data on the rising edge
 
       source_width = 128;
-      source_height = 16;
+      source_height = 32; // is actually 16, but we process as 32
       source_bitsperpixel = 4;  // recorded as 4bpp in the pio
       target_bitsperpixel = 2;  // max pixel value is 3
       // in DE-Sega, there's only one plane,
@@ -1061,7 +1063,7 @@ bool dmdreader_init(bool return_on_no_detection) {
       pio_sm_exec(frame_pio, frame_sm, pio_encode_pull(false, false));
 
       source_width = 128;
-      source_height = 16;
+      source_height = 32; // is actually 16, but we process as 32
       source_bitsperpixel = 4;  // recorded as 4bpp in the pio
       target_bitsperpixel = 2;  // max pixvalues are 0, 1, 2, 3
       // in DE-Sega, there's only one plane,
@@ -1301,6 +1303,13 @@ bool dmdreader_init(bool return_on_no_detection) {
     offset[i] = i * source_dwordsperplane;
   }
 
+  // Read a 128x16 frame but process as 128x32, so, change the number of
+  // transfers at this stage to trigger a dma transfer at the right time.
+  if (dmd_type == DMD_DE_X16_V1 || dmd_type == DMD_DE_X16_V2) {
+      source_dwordsperframe /= 2;
+      source_dwordsperplane /= 2;
+  }
+
   // DMA for DMD reader
   dmd_dma_channel = dma_claim_unused_channel(true);
   dmd_dma_channel_cfg = dma_channel_get_default_config(dmd_dma_channel);