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Merge pull request #335 from TomHarte/BetterTape

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Makes MSX tape parsing more tolerant to phase.
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Thomas Harte 2018-01-10 18:56:44 -08:00 committed by GitHub
commit f354c12c81
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2 changed files with 29 additions and 22 deletions
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17
OSBindings/Mac/Clock Signal/Info.plist
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@ -268,7 +268,6 @@
<key>CFBundleTypeExtensions</key> <key>CFBundleTypeExtensions</key>
<array> <array>
<string>cas</string> <string>cas</string>
<string>tsx</string>
</array> </array>
<key>CFBundleTypeIconFile</key> <key>CFBundleTypeIconFile</key>
<string>cassette</string> <string>cassette</string>
@ -300,6 +299,22 @@
<key>LSTypeIsPackage</key> <key>LSTypeIsPackage</key>
<integer>0</integer> <integer>0</integer>
</dict> </dict>
<dict>
<key>CFBundleTypeExtensions</key>
<array>
<string>tsx</string>
</array>
<key>CFBundleTypeIconFile</key>
<string>cassette</string>
<key>CFBundleTypeName</key>
<string>MSX Tape Image</string>
<key>CFBundleTypeRole</key>
<string>Viewer</string>
<key>LSTypeIsPackage</key>
<integer>0</integer>
<key>NSDocumentClass</key>
<string>$(PRODUCT_MODULE_NAME).MachineDocument</string>
</dict>
</array> </array>
<key>CFBundleExecutable</key> <key>CFBundleExecutable</key>
<string>$(EXECUTABLE_NAME)</string> <string>$(EXECUTABLE_NAME)</string>

34
Storage/Tape/Parsers/MSX.cpp
View File

@ -96,33 +96,25 @@ int Parser::get_byte(const FileSpeed &speed, Storage::Tape::BinaryTapePlayer &ta
"The cassette is first read continuously until a start bit is found. "The cassette is first read continuously until a start bit is found.
This is done by locating a negative transition, measuring the following This is done by locating a negative transition, measuring the following
cycle length (1B1FH) and comparing this to see if it is greater than LOWLIM." cycle length (1B1FH) and comparing this to see if it is greater than LOWLIM."
... but I don't buy that, as it makes the process overly dependent on phase.
So I'm going to look for the next two consecutive pulses that are each big
enough to be half of a zero.
*/ */
float minimum_start_bit_duration = static_cast<float>(speed.minimum_start_bit_duration) * 0.00001145f; const float minimum_start_bit_duration = static_cast<float>(speed.minimum_start_bit_duration) * 0.00001145f * 0.5f;
int input = 0;
while(!tape_player.get_tape()->is_at_end()) { while(!tape_player.get_tape()->is_at_end()) {
// Find a negative transition. // Find next transition.
while(!tape_player.get_tape()->is_at_end() && tape_player.get_input()) {
tape_player.run_for_input_pulse();
}
// Measure the following cycle (i.e. two transitions).
bool level = tape_player.get_input(); bool level = tape_player.get_input();
float time_to_transition = 0.0f; float duration = 0.0;
int transitions = 0; while(level == tape_player.get_input()) {
while(!tape_player.get_tape()->is_at_end()) { duration += static_cast<float>(tape_player.get_cycles_until_next_event()) / static_cast<float>(tape_player.get_input_clock_rate());
time_to_transition += static_cast<float>(tape_player.get_cycles_until_next_event()) / static_cast<float>(tape_player.get_input_clock_rate());
tape_player.run_for_input_pulse(); tape_player.run_for_input_pulse();
if(level != tape_player.get_input()) {
level = tape_player.get_input();
transitions++;
if(transitions == 2)
break;
}
} }
// Check length against 'LOWLIM' (i.e. the minimum start bit duration). input = (input << 1);
if(time_to_transition > minimum_start_bit_duration) { if(duration >= minimum_start_bit_duration) input |= 1;
break; if((input&3) == 3) break;
}
} }
/* /*