Switch the output lines to open-drain drive low.

command.

FluxEngine.cydsn/CortexM3/ARM_GCC_541/Release/FluxEngine.hex

@@ -4122,8 +4122,8 @@
 :400540008B029E80A580AF20C820E280EA4073807F029B80A302AB80DC80DE20EA8005200B800C020D040F08520254205E4061028C028F04924095089780A202AF04C001D7
 :40058000C20DD403D604D802E202E602A920AD02B420EC0801010D010F0111011D0100BD012A10050820324039804620082010C42000080280000000FE1001ED00E3001C2E
 :4005C00000000000000000000000040182EF3D10000000083800C11F07E0000000080220000010004603020000E0000412FFFFFF0020F00120100000000008000404040460
-:4006000099990001000800004020800840200008000040A8000000000000000000000000000000003F00003F1F001F0000000000000000001000000040000000000000003B
-:40064000C0000000FF0020FF4700470000010000A00000BFBF009F00000000000001000000000000000000000000000000000000000000000000000000000000000000004F
+:4006000099990001000800004020800840200008000040A8000000000000000000000000000000003F0000201F001F0000000000000000001000000040000000000000005A
+:40064000C0000000FF0000B84700470000010000A000003FBF009F000000000000010000000000000000000000000000000000000000000000000000000000000000000036
 :40068000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000003A
 :4006C00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000FA
 :4007000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000B9
@@ -4615,12 +4615,12 @@
 :0200000490105A
 :04000000BC90ACAF55
 :0200000490303A
-:020000004C1A98
+:020000004B149F
 :0200000490402A
 :4000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000C0
 :400040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000080
 :400080000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040
 :4000C0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
 :0200000490501A
-:0C00000000012E16106900002E2A5C83FF
+:0C00000000012E16106900002E2A5B7D06
 :00000001FF

Makefile

@@ -1,8 +1,8 @@
 PACKAGES = zlib sqlite3 libusb-1.0
 
-export CFLAGS = -O3 -g --std=c++14 \
+export CFLAGS = -Os -g --std=c++14 \
 	-ffunction-sections -fdata-sections
-export LDFLAGS = -O3
+export LDFLAGS = -Os
 
 ifeq ($(OS), Windows_NT)
 export CXX = /mingw32/bin/g++

doc/disk-brother.md

@@ -129,8 +129,8 @@ reverse engineered it to find out.
 
 Standard Linux mtools will access the filesystem image and allow you to move
 files in and out. However, you'll need to change the media type bytes at
-offsets 0x015 and 0x100 from 0x58 to 0xf0 before mtools will touch it. Once
-done, this will work:
+offsets 0x015 and 0x100 from 0x58 to 0xf0 before mtools will touch it. The
+supplied `brother240tool` will do this. Once done, this will work:
 
 ```
 mdir -i brother.img

doc/technical.md

@@ -123,8 +123,12 @@ admittedly expensive.)
     sheet](http://www.bitsavers.org/pdf/mitsubishi/floppy/M4851/TJ2-G30211A_M4851_DSHH_48TPI_OEM_Manual_Nov83.pdf):
     the equivalent data sheet for a representative 5.25" drive.
 
+  - [The DRG Business Machines YD-174 manual](https://electrickery.hosting.philpem.me.uk/comp/divcomp/doc/YE_Data_YD-174_8inchFloppyDriveTechnicalManual.pdf):
+	the equivalent manual (data sheets hadn't been invented then) for a
+	representative 8" drive.
+
   - [KryoFlux stream file
     documentation](https://www.kryoflux.com/download/kryoflux_stream_protocol_rev1.1.pdf):
     the format of KryoFlux stream files (partially supported by FluxEngine)
 
-  
+  

doc/using.md

@@ -221,6 +221,20 @@ directory.
   file format in a non-backwards-compatible way; this tool will upgrade flux
   files to the new format.
 
+  - `fluxengine convert`: converts flux files from various formats to various
+  other formats. You can use this to convert Catweasel flux files to
+  FluxEngine's native format, FluxEngine flux files to various other formats
+  useful for debugging (including VCD which can be loaded into
+  [sigrok](http://sigrok.org)), and bidirectional conversion to and from
+  Supercard Pro `.scp` format.
+
+  **Important SCP note:** import (`fluxengine convert scptoflux`) should be
+  fairly robust, but export (`fluxengine convert fluxtoscp`) should only be
+  done with great caution as FluxEngine files contain features which can't be
+  represented very well in `.scp` format and they're probably pretty dubious.
+  As ever, please [get in
+  touch](https://github.com/davidgiven/fluxengine/issues/new) with any reports.
+
 Commands which normally take `--source` or `--dest` get a sensible default if
 left unspecified. `fluxengine read ibm` on its own will read drive 0 and
 write an `ibm.img` file.
@@ -247,25 +261,24 @@ wrote to do useful things. These are built alongside FluxEngine.
 
   - `brother120tool`: extracts files from a 120kB Brother filesystem image.
 
-  - `cwftoflux`: converts (one flavour of) CatWeasel flux file into a
-    FluxEngine flux file.
-
 ## The recommended workflow
 
-So you've just received, say, a huge pile of old Brother word processor disks containing valuable historical data, and you want to read them.
+So you've just received, say, a huge pile of old Brother word processor disks
+containing valuable historical data, and you want to read them.
 
 Typically I do this:
 
 ```
-$ fluxengine read brother -s :d=0 -o brother.img --write-flux=brother.flux
+$ fluxengine read brother -s :d=0 -o brother.img --write-flux=brother.flux --write-svg=brother.svg
 ```
 
 This will read the disk in drive 0 and write out a filesystem image. It'll
-also copy the flux to brother.flux. If I then need to tweak the settings, I
-can rerun the decode without having to physically touch the disk like this:
+also copy the flux to brother.flux and write out an SVG visualisation. If I
+then need to tweak the settings, I can rerun the decode without having to
+physically touch the disk like this:
 
 ```
-$ fluxengine read brother -s brother.flux -o brother.img
+$ fluxengine read brother -s brother.flux -o brother.img --write-svg=brother.svg
 ```
 
 Apart from being drastically faster, this avoids touching the (potentially

lib/flags.cc

@@ -29,7 +29,7 @@ void FlagGroup::addFlag(Flag* flag)
     _flags.push_back(flag);
 }
 
-void FlagGroup::parseFlags(int argc, const char* argv[])
+std::vector<std::string> FlagGroup::parseFlagsWithFilenames(int argc, const char* argv[])
 {
     if (_initialised)
         throw std::runtime_error("called parseFlags() twice");
@@ -66,6 +66,7 @@ void FlagGroup::parseFlags(int argc, const char* argv[])
 
     /* Now actually parse them. */
 
+    std::vector<std::string> filenames;
     int index = 1;
     while (index < argc)
     {
@@ -76,52 +77,73 @@ void FlagGroup::parseFlags(int argc, const char* argv[])
         std::string value;
         bool usesthat = false;
 
-        if ((thisarg.size() == 0) || (thisarg[0] != '-'))
-            Error() << "non-option parameter " << thisarg << " seen (try --help)";
-        if ((thisarg.size() > 1) && (thisarg[1] == '-'))
+        if (thisarg.size() == 0)
         {
-            /* Long option. */
-
-            auto equals = thisarg.rfind('=');
-            if (equals != std::string::npos)
-            {
-                key = thisarg.substr(0, equals);
-                value = thisarg.substr(equals+1);
-            }
-            else
-            {
-                key = thisarg;
-                value = thatarg;
-                usesthat = true;
-            }
+            /* Ignore this argument. */
+        }
+        else if (thisarg[0] != '-')
+        {
+            /* This is a filename. */
+            filenames.push_back(thisarg);
         }
         else
         {
-            /* Short option. */
+            /* This is a flag. */
 
-            if (thisarg.size() > 2)
+            if ((thisarg.size() > 1) && (thisarg[1] == '-'))
             {
-                key = thisarg.substr(0, 2);
-                value = thisarg.substr(2);
+                /* Long option. */
+
+                auto equals = thisarg.rfind('=');
+                if (equals != std::string::npos)
+                {
+                    key = thisarg.substr(0, equals);
+                    value = thisarg.substr(equals+1);
+                }
+                else
+                {
+                    key = thisarg;
+                    value = thatarg;
+                    usesthat = true;
+                }
             }
             else
             {
-                key = thisarg;
-                value = thatarg;
-                usesthat = true;
+                /* Short option. */
+
+                if (thisarg.size() > 2)
+                {
+                    key = thisarg.substr(0, 2);
+                    value = thisarg.substr(2);
+                }
+                else
+                {
+                    key = thisarg;
+                    value = thatarg;
+                    usesthat = true;
+                }
             }
+
+            auto flag = flags_by_name.find(key);
+            if (flag == flags_by_name.end())
+                Error() << "unknown flag '" << key << "'; try --help";
+
+            flag->second->set(value);
+            if (usesthat && flag->second->hasArgument())
+                index++;
         }
 
-        auto flag = flags_by_name.find(key);
-        if (flag == flags_by_name.end())
-            Error() << "unknown flag '" << key << "'; try --help";
-
-        flag->second->set(value);
-
         index++;
-        if (usesthat && flag->second->hasArgument())
-            index++;
     }
+
+    return filenames;
+}
+
+void FlagGroup::parseFlags(int argc, const char* argv[])
+{
+    auto filenames = parseFlagsWithFilenames(argc, argv);
+    if (!filenames.empty())
+        Error() << "non-option parameter " << *filenames.begin() << " seen (try --help)";
 }
 
 void FlagGroup::checkInitialised() const

lib/flags.h

@@ -14,6 +14,7 @@ public:
 
 public:
     void parseFlags(int argc, const char* argv[]);
+    std::vector<std::string> parseFlagsWithFilenames(int argc, const char* argv[]);
     void addFlag(Flag* flag);
     void checkInitialised() const;
 

mkninja.sh

@@ -190,6 +190,7 @@ buildlibrary libfrontend.a \
     src/fe-cwftoflux.cc \
     src/fe-erase.cc \
     src/fe-fluxtoau.cc \
+    src/fe-fluxtoscp.cc \
     src/fe-fluxtovcd.cc \
     src/fe-inspect.cc \
     src/fe-readadfs.cc \
@@ -208,6 +209,7 @@ buildlibrary libfrontend.a \
     src/fe-readvictor9k.cc \
     src/fe-readzilogmcz.cc \
     src/fe-rpm.cc \
+    src/fe-scptoflux.cc \
     src/fe-seek.cc \
     src/fe-testbulktransport.cc \
     src/fe-upgradefluxfile.cc \
@@ -231,6 +233,13 @@ buildsimpleprogram brother120tool \
     libemu.a \
     libfmt.a \
 
+buildsimpleprogram brother240tool \
+	-Idep/emu \
+    tools/brother240tool.cc \
+    libbackend.a \
+    libemu.a \
+    libfmt.a \
+
 runtest bitaccumulator-test tests/bitaccumulator.cc
 runtest bytes-test          tests/bytes.cc
 runtest compression-test    tests/compression.cc

src/fe-erase.cc

@@ -3,7 +3,7 @@
 #include "fluxmap.h"
 #include "writer.h"
 
-static FlagGroup flags;
+static FlagGroup flags { &writerFlags };
 
 int mainErase(int argc, const char* argv[])
 {

src/fe-fluxtoscp.cc

@@ -0,0 +1,188 @@
+#include "globals.h"
+#include "flags.h"
+#include "fluxmap.h"
+#include "sql.h"
+#include "bytes.h"
+#include "protocol.h"
+#include "dataspec.h"
+#include "fmt/format.h"
+#include "decoders/fluxmapreader.h"
+#include "scp.h"
+#include <fstream>
+#include <algorithm>
+
+static FlagGroup flags { };
+
+static SettableFlag fortyTrackMode(
+    { "--48", "-4" },
+    "set 48 tpi mode; only every other physical track is emitted"
+);
+
+static SettableFlag singleSided(
+    { "--single-sided", "-s" },
+    "only emit side 0"
+);
+
+static IntFlag diskType(
+    { "--disk-type" },
+    "sets the SCP disk type byte",
+    0xff
+);
+
+static sqlite3* inputDb;
+
+static void syntax()
+{
+    std::cout << "Syntax: fluxengine convert fluxtoscp <fluxfile> <scpfile>\n";
+    exit(0);
+}
+
+static void write_le32(uint8_t dest[4], uint32_t v)
+{
+    dest[0] = v;
+    dest[1] = v >> 8;
+    dest[2] = v >> 16;
+    dest[3] = v >> 24;
+}
+
+static int strackno(int track, int side)
+{
+    if (fortyTrackMode)
+        track /= 2;
+    if (singleSided)
+        return track;
+    else
+        return (track << 1) | side;
+}
+
+int mainConvertFluxToScp(int argc, const char* argv[])
+{
+    auto filenames = flags.parseFlagsWithFilenames(argc, argv);
+    if (filenames.size() != 2)
+        syntax();
+
+    inputDb = sqlOpen(filenames[0], SQLITE_OPEN_READONLY);
+    auto tracks = sqlFindFlux(inputDb);
+
+    int maxTrack = 0;
+    int maxSide = 0;
+    for (auto p : tracks)
+    {
+        if (singleSided && (p.second == 1))
+            continue;
+        maxTrack = std::max(maxTrack, (int)p.first);
+        maxSide = std::max(maxSide, (int)p.second);
+    }
+    int maxStrack = strackno(maxTrack, maxSide);
+
+    std::cout << fmt::format("Writing {} {} SCP file containing {} SCP tracks\n",
+        fortyTrackMode ? "48 tpi" : "96 tpi",
+        singleSided ? "single sided" : "double sided",
+        maxStrack + 1
+    );
+
+    ScpHeader fileheader = {0};
+    fileheader.file_id[0] = 'S';
+    fileheader.file_id[1] = 'C';
+    fileheader.file_id[2] = 'P';
+    fileheader.file_id[3] = 0x18; /* Version 1.8 of the spec */
+    fileheader.type = diskType;
+    fileheader.revolutions = 5;
+    fileheader.start_track = 0;
+    fileheader.end_track = maxStrack;
+    fileheader.flags = SCP_FLAG_INDEXED | (fortyTrackMode ? 0 : SCP_FLAG_96TPI);
+    fileheader.cell_width = 0;
+    fileheader.heads = singleSided ? 1 : 0;
+
+    Bytes trackdata;
+    ByteWriter trackdataWriter(trackdata);
+
+    int trackstep = 1 + fortyTrackMode;
+    int maxside = singleSided ? 0 : 1;
+    for (int track = 0; track <= maxTrack; track += trackstep)
+    {
+        for (int side = 0; side <= maxside; side++)
+        {
+            int strack = strackno(track, side);
+            std::cout << fmt::format("FE track {}.{}, SCP track {}: ", track, side, strack) << std::flush;
+
+            auto fluxmap = sqlReadFlux(inputDb, track, side);
+            ScpTrack trackheader = {0};
+            trackheader.track_id[0] = 'T';
+            trackheader.track_id[1] = 'R';
+            trackheader.track_id[2] = 'K';
+            trackheader.strack = strack;
+
+            FluxmapReader fmr(*fluxmap);
+            Bytes fluxdata;
+            ByteWriter fluxdataWriter(fluxdata);
+
+            int revolution = 0;
+            unsigned revTicks = 0;
+            unsigned totalTicks = 0;
+            unsigned ticksSinceLastPulse = 0;
+            uint32_t startOffset = 0;
+            while (revolution < 5)
+            {
+                unsigned ticks;
+                int opcode = fmr.readOpcode(ticks);
+                if (ticks)
+                {
+                    ticksSinceLastPulse += ticks;
+                    totalTicks += ticks;
+                    revTicks += ticks;
+                }
+
+                switch (opcode)
+                {
+                    case -1: /* end of flux, treat like an index marker */
+                    case F_OP_INDEX:
+                    {
+                        auto* revheader = &trackheader.revolution[revolution];
+                        write_le32(revheader->offset, startOffset + sizeof(ScpTrack));
+                        write_le32(revheader->length, (fluxdataWriter.pos - startOffset) / 2);
+                        write_le32(revheader->index, revTicks * NS_PER_TICK / 25);
+                        revolution++;
+                        revheader++;
+                        revTicks = 0;
+                        startOffset = fluxdataWriter.pos;
+                        break;
+                    }
+
+                    case F_OP_PULSE:
+                    {
+                        unsigned t = ticksSinceLastPulse * NS_PER_TICK / 25;
+                        while (t >= 0x10000)
+                        {
+                            fluxdataWriter.write_be16(0);
+                            t -= 0x10000;
+                        }
+                        fluxdataWriter.write_be16(t);
+                        ticksSinceLastPulse = 0;
+                        break;
+                    }
+                }
+            }
+
+            write_le32(fileheader.track[strack], trackdataWriter.pos + sizeof(ScpHeader));
+            trackdataWriter += Bytes((uint8_t*)&trackheader, sizeof(trackheader));
+            trackdataWriter += fluxdata;
+
+            std::cout << fmt::format("{} ms in {} bytes\n",
+                totalTicks * MS_PER_TICK,
+                fluxdata.size());
+        }
+    }
+
+    sqlClose(inputDb);
+    
+    std::cout << "Writing output file...\n";
+    std::ofstream of(filenames[1], std::ios::out | std::ios::binary);
+    if (!of.is_open())
+        Error() << "cannot open output file";
+    of.write((const char*) &fileheader, sizeof(fileheader));
+    of.write((const char*) trackdata.begin(), trackdata.size());
+    of.close();
+
+    return 0;
+}

src/fe-rpm.cc

@@ -8,7 +8,7 @@ static FlagGroup flags;
 static DataSpecFlag source(
     { "--source", "-s" },
     "source for data",
-    ":d=0");
+    ":d=0:t=0:s=0");
 
 int mainRpm(int argc, const char* argv[])
 {

src/fe-scptoflux.cc

@@ -0,0 +1,142 @@
+#include "globals.h"
+#include "fluxmap.h"
+#include "sql.h"
+#include "bytes.h"
+#include "protocol.h"
+#include "fmt/format.h"
+#include "scp.h"
+#include <fstream>
+
+static std::ifstream inputFile;
+static sqlite3* outputDb;
+static ScpHeader header;
+static nanoseconds_t resolution;
+static int startSide;
+static int endSide;
+
+static void syntax()
+{
+    std::cout << "Syntax: fluxengine convert cwftoflux <cwffile> <fluxfile>\n";
+    exit(0);
+}
+
+static void check_for_error()
+{
+    if (inputFile.fail())
+        Error() << fmt::format("I/O error: {}", strerror(errno));
+}
+
+static int trackno(int strack)
+{
+    if (startSide == endSide)
+        return strack;
+    return strack >> 1;
+}
+
+static int headno(int strack)
+{
+    if (startSide == endSide)
+        return startSide;
+    return strack & 1;
+}
+
+static void read_header()
+{
+    inputFile.read((char*) &header, sizeof(header));
+    check_for_error();
+
+    if ((header.file_id[0] != 'S')
+            || (header.file_id[1] != 'C')
+            || (header.file_id[2] != 'P'))
+        Error() << "input not a SCP file";
+
+    resolution = 25 * (header.resolution + 1);
+    startSide = (header.heads == 2) ? 1 : 0;
+    endSide = (header.heads == 1) ? 0 : 1;
+
+    if ((header.cell_width != 0) && (header.cell_width != 16))
+        Error() << "currently only 16-bit cells are supported";
+
+    std::cout << fmt::format("tracks {}-{}, heads {}-{}\n",
+        trackno(header.start_track), trackno(header.end_track), startSide, endSide);
+    std::cout << fmt::format("sample resolution: {} ns\n", resolution);
+}
+
+static void read_track(int strack)
+{
+    uint32_t offset = Bytes(header.track[strack], 4).reader().read_le32();
+
+    ScpTrack trackheader;
+    inputFile.seekg(offset, std::ios::beg);
+    inputFile.read((char*) &trackheader, sizeof(trackheader));
+    check_for_error();
+
+    if ((trackheader.track_id[0] != 'T')
+            || (trackheader.track_id[1] != 'R')
+            || (trackheader.track_id[2] != 'K'))
+        Error() << "corrupt SCP file";
+
+    std::cout << fmt::format("{}.{}: ", trackno(strack), headno(strack))
+        << std::flush;
+
+    Fluxmap fluxmap;
+    nanoseconds_t pending = 0;
+    unsigned inputBytes = 0;
+    for (int revolution = 0; revolution < header.revolutions; revolution++)
+    {
+        if (revolution != 0)
+            fluxmap.appendIndex();
+
+        uint32_t datalength = Bytes(trackheader.revolution[revolution].length, 4).reader().read_le32();
+        uint32_t dataoffset = Bytes(trackheader.revolution[revolution].offset, 4).reader().read_le32();
+
+        Bytes data(datalength*2);
+        inputFile.seekg(dataoffset + offset, std::ios::beg);
+        inputFile.read((char*) data.begin(), data.size());
+        check_for_error();
+
+        ByteReader br(data);
+        for (int cell = 0; cell < datalength; cell++)
+        {
+            uint16_t interval = br.read_be16();
+            if (interval)
+            {
+                fluxmap.appendInterval((interval + pending) * resolution / NS_PER_TICK);
+                fluxmap.appendPulse();
+                pending = 0;
+            }
+            else
+                pending += 0x10000;
+        }
+
+        inputBytes += datalength*2;
+    }
+
+    std::cout << fmt::format(" {} ms in {} input bytes and {} output bytes\n",
+        fluxmap.duration() / 1e6, inputBytes, fluxmap.bytes());
+    sqlWriteFlux(outputDb, trackno(strack), headno(strack), fluxmap);
+}
+
+int mainConvertScpToFlux(int argc, const char* argv[])
+{
+    if (argc != 3)
+        syntax();
+    
+    inputFile.open(argv[1], std::ios::in | std::ios::binary);
+    if (!inputFile.is_open())
+		Error() << fmt::format("cannot open input file '{}'", argv[1]);
+
+    outputDb = sqlOpen(argv[2], SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE);
+    sqlPrepareFlux(outputDb);
+    sqlWriteIntProperty(outputDb, "version", FLUX_VERSION_CURRENT);
+    sqlStmt(outputDb, "BEGIN;");
+
+    read_header();
+    inputFile.seekg(sizeof(header), std::ios::beg);
+    for (unsigned i=header.start_track; i<=header.end_track; i++)
+        read_track(i);
+
+    sqlStmt(outputDb, "COMMIT;");
+    sqlClose(outputDb);
+    return 0;
+}

src/fluxengine.cc

@@ -5,7 +5,9 @@ typedef int command_cb(int agrc, const char* argv[]);
 extern command_cb mainErase;
 extern command_cb mainConvertCwfToFlux;
 extern command_cb mainConvertFluxToAu;
+extern command_cb mainConvertFluxToScp;
 extern command_cb mainConvertFluxToVcd;
+extern command_cb mainConvertScpToFlux;
 extern command_cb mainInspect;
 extern command_cb mainReadADFS;
 extern command_cb mainReadAESLanier;
@@ -83,7 +85,9 @@ static std::vector<Command> writeables =
 static std::vector<Command> convertables =
 {
     { "cwftoflux",     mainConvertCwfToFlux, "Converts CatWeasel stream files to flux.", },
+    { "scptoflux",     mainConvertScpToFlux, "Converts Supercard Pro stream files to flux.", },
     { "fluxtoau",      mainConvertFluxToAu,  "Converts (one track of a) flux file to an .au audio file.", },
+    { "fluxtoscp",     mainConvertFluxToScp, "Converrt a flux file to a Supercard Pro file.", },
     { "fluxtovcd",     mainConvertFluxToVcd, "Converts (one track of a) flux file to a VCD file.", },
 };
 

src/scp.h

@@ -0,0 +1,43 @@
+#ifndef SCP_H
+#define SCP_H
+
+struct ScpHeader
+{
+    char file_id[3];       // file ID - 'SCP'
+    uint8_t version;       // major/minor in nibbles
+    uint8_t type;          // disk type - subclass/class in nibbles
+    uint8_t revolutions;   // up to 5
+    uint8_t start_track;   // 0..165
+    uint8_t end_track;     // 0..165
+    uint8_t flags;         // see below
+    uint8_t cell_width;    // in bits, 0 meaning 16
+    uint8_t heads;         // 0 = both, 1 = side 0 only, 2 = side 1 only
+    uint8_t resolution;    // 25ns * (resolution+1)
+    uint8_t checksum[4];   // of data after this point
+    uint8_t track[165][4]; // track offsets, not necessarily 165
+};
+
+enum
+{
+    SCP_FLAG_INDEXED    = (1<<0),
+    SCP_FLAG_96TPI      = (1<<1),
+    SCP_FLAG_360RPM     = (1<<2),
+    SCP_FLAG_NORMALIZED = (1<<3),
+    SCP_FLAG_READWRITE  = (1<<4),
+    SCP_FLAG_FOOTER     = (1<<5)
+};
+
+struct ScpTrack
+{
+    char track_id[3];      // 'TRK'
+    uint8_t strack;        // SCP track number
+    struct
+    {
+        uint8_t index[4];  // time for one revolution
+        uint8_t length[4]; // number of bitcells
+        uint8_t offset[4]; // offset to bitcell data, relative to track header
+    }
+    revolution[5];
+};
+
+#endif

tools/brother240tool.cc

@@ -0,0 +1,56 @@
+#include "globals.h"
+#include "fmt/format.h"
+#include <fstream>
+
+static std::fstream inputFile;
+
+void syntax()
+{
+    std::cout << "Syntax: brother240tool <image>\n"
+                 "The disk image will be flipped from Brother to DOS format and back\n"
+                 "again.\n";
+    exit(0);
+}
+
+uint8_t getbyte(uint32_t offset)
+{
+    inputFile.seekg(offset, std::ifstream::beg);
+    return inputFile.get();
+}
+
+void putbyte(uint32_t offset, uint8_t value)
+{
+    inputFile.seekp(offset, std::ifstream::beg);
+    inputFile.put(value);
+}
+
+int main(int argc, const char* argv[])
+{
+    if (argc < 2)
+        syntax();
+    
+    inputFile.open(argv[1], std::ios::in | std::ios::out | std::ios::binary);
+    if (!inputFile.is_open())
+		Error() << fmt::format("cannot open input file '{}'", argv[1]);
+
+    uint8_t b1 = getbyte(0x015);
+    uint8_t b2 = getbyte(0x100);
+    if ((b1 == 0x58) && (b2 == 0x58))
+    {
+        std::cerr << "Flipping from Brother to DOS.\n";
+        putbyte(0x015, 0xf0);
+        putbyte(0x100, 0xf0);
+    }
+    else if ((b1 == 0xf0) && (b2 == 0xf0))
+    {
+        std::cerr << "Flipping from DOS to Brother.\n";
+        putbyte(0x015, 0x58);
+        putbyte(0x100, 0x58);
+    }
+    else
+        Error() << "Unknown image format.";
+
+    inputFile.close();
+    return 0;
+}
+