Initial commit

.gitignore

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+samples/

README.md

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+# Intro
+
+Mobitec flip-disc displays use MC27C1001 EPROM-s to store the
+firmware (?) and fonts.
+In the `firmware/` directory you can find two ROM dumps.
+
+# Useful commands
+
+To extract font sections:
+
+```
+dd if=mobitec-1682-r7-bib-01979-r3.bin of=mobitec-1682-r7-bib-01979-r3-fonts.bin skip=64 bs=1024
+dd if=mobitec-01682-r7-bib-01369-r9.bin of=mobitec-01682-r7-bib-01369-r9-fonts.bin skip=64 bs=1024
+```
+
+For diffing font sections:
+
+```
+dhex mobitec-1682-r7-bib-01979-r3-fonts.bin mobitec-01682-r7-bib-01369-r9-fonts.bin
+```
+
+# Dump structure
+
+The firmware seems to be located in the first 7KiB and the font data
+starts at 0x10000 offset.
+
+The font beginning marker seem to consist of a character from `a` to `z`
+followed by at least 60 null characters.
+They don't seem aligned or indexed in any way so easiest is just to scan
+for known markers.
+
+After the beginning marker you can find the lookup table which maps
+printable ASCII characters to a glyph address.
+The lookup table is 190 bytes (95x 16-bit addresses) which correspond
+to ASCII characters 32 up to 126.
+Not all fonts include all characters, missing glyphs are represented by address 0.
+Note that the glyph address is relative to the beginning of font structure,
+beginning marker inclusive.
+
+At the glyph address first width and height of the glyph are found represented
+by two 8-bit integers. The actual bitmap data follows in 8x8 pixel tiles
+packed together as 8 bytes.
+
+

extract-fonts.py

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+import json
+import cv2
+import numpy as np
+
+"""
+dd if=mobitec-1682-r7-bib-01979-r3.bin of=mobitec-1682-r7-bib-01979-r3-fonts.bin skip=64 bs=1024
+dd if=mobitec-01682-r7-bib-01369-r9.bin of=mobitec-01682-r7-bib-01369-r9-fonts.bin skip=64 bs=1024
+dhex mobitec-1682-r7-bib-01979-r3-fonts.bin mobitec-01682-r7-bib-01369-r9-fonts.bin
+"""
+
+src = "mobitec-1682-r7-bib-01979-r3"
+src = "mobitec-01682-r7-bib-01369-r9"
+
+with open("firmware/%s.bin" % src, "rb") as fh:
+    buf = fh.read()[65536:]
+
+
+def scan_fonts(buf):
+    """
+    Font start markers seem to be ascii character a..z followed by at least 60 nulls
+    """
+    font_index = buf[0]
+    assert font_index == 0x61
+    prev = 0
+    done = False
+    while not done:
+        needle = b"%c" % (font_index + 1)
+        needle += 50 * b"\x00"
+        try:
+            font_offset = buf.index(needle)
+        except ValueError:
+            break
+            font_body = buf[prev:]
+            done = True
+        else:
+            font_body = buf[prev:font_offset]
+        if done:
+            break
+        font_marker_length = len(needle)
+        font_body = font_body[font_marker_length:]
+        while font_body.startswith(b"\x00"):
+            font_body = font_body[1:]
+            font_marker_length += 1
+        yield font_index, font_body, font_marker_length
+        prev = font_offset
+        font_index += 1
+
+
+meta = []
+for font_index, font_body, font_marker_length in scan_fonts(buf):
+    print()
+    print("Parsing font %02x" % font_index)
+
+    # Looks like yet another marker
+    assert font_body[0] == 3
+    assert font_body[1] == 1
+
+    # Look up table consists of 95 16-bit integers
+    glyph_offsets = np.frombuffer(font_body[2:192], dtype=np.uint16)
+    prev = 0
+    slices = []
+    errors = set()
+
+    for index, glyph_offset in enumerate(glyph_offsets):
+        if glyph_offset != 0:
+            glyph_offset -= font_marker_length
+            print("Found %d undecoded bytes between lookup table and first glyph" % len(font_body[192:192 + glyph_offset]))
+            break
+
+    characters_present = ""
+
+    for index, glyph_offset in enumerate(glyph_offsets):
+        if glyph_offset == 0:
+            characters_present += "_"
+            # No glyph
+            meta.append(None)
+            continue
+        else:
+            # The index goes from space (32) up to ~ (126)
+            character = chr(index + 32)
+            characters_present += "+"
+
+        # Glyphs are relative to the font marker start
+        glyph_offset -= font_marker_length
+
+        try:
+            height, width = font_body[glyph_offset], font_body[glyph_offset + 1]
+        except IndexError:
+            print("Failed to look up glyph for %s", repr(character))
+        else:
+            jah = np.frombuffer((font_body[glyph_offset + 2:])[::-1], dtype=np.uint8)[::-1]
+            a = np.unpackbits(jah, axis=0)
+            try:
+                img = a[:width * 16].reshape((width, 16, 1))
+                img = np.hstack([img[:, 8:, :], img[:, :8, :]])
+                meta.append({
+                    "width": width,
+                    "height": height,
+                    "bitmap": img.tolist()
+                })
+                img = 255 * img
+
+                slices.append(img)
+            except ValueError:
+                pass
+            else:
+                blank_image = np.zeros((1, 16, 1), np.uint8)
+                blank_image[::] = 0
+                slices.append(blank_image)
+
+        if glyph_offset <= prev:
+            print("Glyph offsets not ordered")
+        prev = glyph_offset
+    print("Glyphs present:", characters_present)
+    img = np.vstack(slices)
+
+    img = np.flip(np.swapaxes(img, 1, 0), 0)
+    s = img.shape * np.array(5)
+    img = cv2.resize(img, dsize=(s[1], s[0]), interpolation=cv2.INTER_NEAREST)
+    cv2.imwrite("samples/%s-%02x.png" % (src, font_index), img)
+    with open("samples/%s-%02x.json" % (src, font_index), "w") as fh:
+        fh.write(json.dumps({"glyphs": meta}))