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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
View File

@ -268,7 +268,6 @@
<key>CFBundleTypeExtensions</key>
<array>
<string>cas</string>
<string>tsx</string>
</array>
<key>CFBundleTypeIconFile</key>
<string>cassette</string>
@ -300,6 +299,22 @@
<key>LSTypeIsPackage</key>
<integer>0</integer>
</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>$(PRODUCT_MODULE_NAME).MachineDocument</string>
</dict>
</array>
<key>CFBundleExecutable</key>
<string>$(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.
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."
... 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()) {
// Find a negative 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).
// Find next transition.
bool level = tape_player.get_input();
float time_to_transition = 0.0f;
int transitions = 0;
while(!tape_player.get_tape()->is_at_end()) {
time_to_transition += static_cast<float>(tape_player.get_cycles_until_next_event()) / static_cast<float>(tape_player.get_input_clock_rate());
float duration = 0.0;
while(level == tape_player.get_input()) {
duration += 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();
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).
if(time_to_transition > minimum_start_bit_duration) {
break;
}
input = (input << 1);
if(duration >= minimum_start_bit_duration) input |= 1;
if((input&3) == 3) break;
}
/*