Merge pull request #12 from adafruit/floppsy-revb-fat-archiver

Update for floppsy rev b & add DOS floppy archiver

Author: jepler

adafruit_floppy.py

@@ -12,6 +12,7 @@
 * Author(s): Jeff Epler
 """
 
+import struct
 import floppyio
 from digitalio import DigitalInOut, Pull
 from micropython import const
@@ -55,7 +56,7 @@ class Floppy:  # pylint: disable=too-many-instance-attributes
 
     _track: typing.Optional[int]
 
-    def __init__(
+    def __init__(  # pylint: disable=too-many-locals
         self,
         *,
         densitypin: microcontroller.Pin,
@@ -72,6 +73,7 @@ def __init__(
         wrdatapin: typing.Optional[microcontroller.Pin] = None,
         wrgatepin: typing.Optional[microcontroller.Pin] = None,
         floppydirectionpin: typing.Optional[microcontroller.Pin] = None,
+        floppyenablepin: typing.Optional[microcontroller.Pin] = None,
     ) -> None:
         self._density = DigitalInOut(densitypin)
         self._density.pull = Pull.UP
@@ -102,6 +104,10 @@ def __init__(
         if self._floppydirection:
             self._floppydirection.switch_to_output(True)
 
+        self._floppyenable = _optionaldigitalinout(floppyenablepin)
+        if self._floppyenable:
+            self._floppyenable.switch_to_output(False)
+
         self._track = None
 
     def _do_step(self, direction, count):
@@ -156,10 +162,12 @@ def track(self, track: int) -> None:
             raise ValueError("Invalid seek to negative track number")
 
         delta = track - self.track
-        if delta < 0:
-            self._do_step(_STEP_OUT, -delta)
-        elif delta > 0:
-            self._do_step(_STEP_IN, delta)
+        if delta:
+            if delta < 0:
+                self._do_step(_STEP_OUT, -delta)
+            elif delta > 0:
+                self._do_step(_STEP_IN, delta)
+            _sleep_ms(_STEP_DELAY_MS)
 
         self._track = track
         self._check_inpos()
@@ -205,7 +213,7 @@ def side(self) -> int:
     def side(self, head: int) -> None:
         self._side.value = head == 0
 
-    def flux_readinto(self, buf: "circuitpython_typing.WritableBuffer") -> int:
+    def flux_readinto(self, buf: "circuitpython_typing.WriteableBuffer") -> int:
         """Read flux transition information into the buffer.
 
         The function returns when the buffer has filled, or when the index input
@@ -222,7 +230,8 @@ def flux_readinto(self, buf: "circuitpython_typing.WritableBuffer") -> int:
 class FloppyBlockDevice:  # pylint: disable=too-many-instance-attributes
     """Wrap an MFMFloppy object into a block device suitable for `storage.VfsFat`
 
-    The default heads/sectors/tracks setting are for 3.5", 1.44MB floppies.
+    The default is to autodetect the data rate and the geometry of an inserted
+    floppy using the floppy's "BIOS paramter block"
 
     In the current implementation, the floppy is read-only.
 
@@ -243,30 +252,75 @@ class FloppyBlockDevice:  # pylint: disable=too-many-instance-attributes
     def __init__(  # pylint: disable=too-many-arguments
         self,
         floppy,
-        heads=2,
-        sectors=18,
-        tracks=80,
-        flux_buffer=None,
-        t1_nom_ns: float = 1000,
+        *,
+        max_sectors=18,
+        autodetect: bool = True,
+        heads: int | None = None,
+        sectors: int | None = None,
+        tracks: int | None = None,
+        flux_buffer: circuitpython_typing.WriteableBuffer | None = None,
+        t1_nom_ns: float | None = None,
+        keep_selected: bool = False,
     ):
         self.floppy = floppy
-        self.heads = heads
-        self.sectors = sectors
-        self.tracks = tracks
-        self.flux_buffer = flux_buffer or bytearray(sectors * 12 * 512)
-        self.track0side0_cache = memoryview(bytearray(sectors * 512))
-        self.track0side0_validity = bytearray(sectors)
-        self.track_cache = memoryview(bytearray(sectors * 512))
-        self.track_validity = bytearray(sectors)
+        self.flux_buffer = flux_buffer or bytearray(max_sectors * 12 * 512)
+        self.track0side0_cache = memoryview(bytearray(max_sectors * 512))
+        self.track_cache = memoryview(bytearray(max_sectors * 512))
+        self._keep_selected = keep_selected
+        self.cached_track = -1
+        self.cached_side = -1
 
-        self._t2_5_max = round(2.5 * t1_nom_ns * floppyio.samplerate * 1e-9)
-        self._t3_5_max = round(3.5 * t1_nom_ns * floppyio.samplerate * 1e-9)
+        if autodetect:
+            self.autodetect()
+        else:
+            self.setformat(heads, sectors, tracks, t1_nom_ns)
+
+        if keep_selected:
+            self.floppy.selected = True
+            self.floppy.spin = True
+
+    @property
+    def keep_selected(self) -> bool:
+        """Whether to keep the drive selected & spinning between operations
+
+        This can make operations faster by avoiding spin up time"""
+        return self._keep_selected
+
+    @keep_selected.setter
+    def keep_selected(self, value: bool):
+        self.floppy.selected = value
+        self.floppy.spin = value
+
+    def _select_and_spin(self, value: bool):
+        if self.keep_selected:
+            return
+        self.floppy.selected = value
+        self.floppy.spin = value
+
+    def on_disk_change(self):
+        """This function (or autodetect or setformat) must be called after a disk is changed
+
+        Flushes the cached floppy data"""
 
         self._track_read(self.track0side0_cache, self.track0side0_validity, 0, 0)
 
         self.cached_track = -1
         self.cached_side = -1
 
+    def setformat(self, heads, sectors, tracks, t1_nom_ns):
+        """Set the floppy format details
+
+        This also calls on_disk_change to flush cached floppy data."""
+        self.heads = heads
+        self.sectors = sectors
+        self.tracks = tracks
+        self._t1_nom_ns = t1_nom_ns
+        self._t2_5_max = round(2.5 * t1_nom_ns * floppyio.samplerate * 1e-9)
+        self._t3_5_max = round(3.5 * t1_nom_ns * floppyio.samplerate * 1e-9)
+        self.track0side0_validity = bytearray(sectors)
+        self.track_validity = bytearray(sectors)
+        self.on_disk_change()
+
     def deinit(self):
         """Deinitialize this object"""
         self.floppy.deinit()
@@ -311,22 +365,25 @@ def _get_track_data(self, track, side):
         return self.track_cache, self.track_validity
 
     def _track_read(self, track_data, validity, track, side):
-        self.floppy.selected = True
-        self.floppy.spin = True
+        self._select_and_spin(True)
         self.floppy.track = track
         self.floppy.side = side
         self._mfm_readinto(track_data, validity)
-        self.floppy.spin = False
-        self.floppy.selected = False
+        self._select_and_spin(False)
         self.cached_track = track
         self.cached_side = side
 
     def _mfm_readinto(self, track_data, validity):
+        n = 0
+        exc = None
         for i in range(5):
-            self.floppy.flux_readinto(self.flux_buffer)
-            print("timing bins", self._t2_5_max, self._t3_5_max)
+            try:
+                self.floppy.flux_readinto(self.flux_buffer)
+            except RuntimeError as error:
+                exc = error
+                continue
             n = floppyio.mfm_readinto(
-                track_data,
+                track_data[: 512 * self.sectors],
                 self.flux_buffer,
                 self._t2_5_max,
                 self._t3_5_max,
@@ -335,3 +392,89 @@ def _mfm_readinto(self, track_data, validity):
             )
             if n == self.sectors:
                 break
+        if n == 0 and exc is not None:
+            raise exc
+
+    def _detect_diskformat_from_flux(self):
+        sector = self.track_cache[:512]
+        # The first two numbers are HD and DD rates. The next two are the bit
+        # rates for 300RPM media read in a 360RPM drive.
+        for t1_nom_ns in [1_000, 2_000, 8_33, 1_667]:
+            t2_5_max = round(2.5 * t1_nom_ns * floppyio.samplerate * 1e-9)
+            t3_5_max = round(3.5 * t1_nom_ns * floppyio.samplerate * 1e-9)
+
+            n = floppyio.mfm_readinto(
+                sector,
+                self.flux_buffer,
+                t2_5_max,
+                t3_5_max,
+            )
+
+            if n == 0:
+                continue
+
+            if sector[510] != 0x55 or sector[511] != 0xAA:
+                print("did not find boot signature 55 AA")
+                print(
+                    "First 16 bytes in sector:",
+                    " ".join("%02x" % c for c in sector[:16]),
+                )
+                print(
+                    "Final 16 bytes in sector:",
+                    " ".join("%02x" % c for c in sector[-16:]),
+                )
+                continue
+
+            n_sectors_track = sector[0x18]
+            n_heads = sector[0x1A]
+            if n_heads != 2:
+                print(f"unsupported head count {n_heads=}")
+                continue
+            n_sectors_total = struct.unpack("<H", sector[0x13:0x15])[0]
+            n_tracks = n_sectors_total // (n_heads * n_sectors_track)
+            f_tracks = n_sectors_total % (n_heads * n_sectors_track)
+            if f_tracks != 0:
+                # pylint: disable=line-too-long
+                print(
+                    f"Dubious geometry! {n_sectors_total=} {n_sectors_track=} {n_heads=} is {n_tracks=}+{f_tracks=}"
+                )
+                n_tracks += 1
+
+            return {
+                "heads": n_heads,
+                "sectors": n_sectors_track,
+                "tracks": n_tracks,
+                "t1_nom_ns": t1_nom_ns,
+            }
+
+    def autodetect(self):
+        """Detect an inserted DOS floppy
+
+        The floppy must have a standard MFM data rate & DOS 2.0 compatible Bios
+        Parameter Block (BPB).  Almost all FAT formatted floppies for DOS & Windows
+        should autodetect in this way.
+
+        This also flushes the cached data.
+        """
+        self._select_and_spin(True)
+        self.floppy.track = 1
+        self.floppy.track = 0
+        self.floppy.side = 0
+        exc = None
+        try:
+            for _ in range(5):  # try repeatedly to read track 0 side 0 sector 0
+                try:
+                    self.floppy.flux_readinto(self.flux_buffer)
+                except RuntimeError as error:
+                    exc = error
+                    continue
+                diskformat = self._detect_diskformat_from_flux()
+                if diskformat is not None:
+                    break
+        finally:
+            self._select_and_spin(False)
+
+        if diskformat is not None:
+            self.setformat(**diskformat)
+        else:
+            raise OSError("Failed to detect floppy format") from exc

docs/api.rst

@@ -1,3 +1,5 @@
+API Documentation
+-----------------
 
 .. If you created a package, create one automodule per module in the package.