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author | 2015-11-08 12:56:12 +0100 | |
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committer | 2015-11-08 12:56:12 +0100 | |
commit | 7c19aac60e12d6f5ea301bdb34d7826a01e0b06f (patch) | |
tree | f310d86aa2c6bfc19d115307dedde4eb0cd52dad /src/lib/formats/atom_tap.cpp | |
parent | a57b46ae933badd7441ce1644711dbb851e2b504 (diff) |
Rename *.c -> *.cpp in our source (nw)
Diffstat (limited to 'src/lib/formats/atom_tap.cpp')
-rw-r--r-- | src/lib/formats/atom_tap.cpp | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/src/lib/formats/atom_tap.cpp b/src/lib/formats/atom_tap.cpp new file mode 100644 index 00000000000..06d614a10b3 --- /dev/null +++ b/src/lib/formats/atom_tap.cpp @@ -0,0 +1,147 @@ +// license:BSD-3-Clause +// copyright-holders:Curt Coder +/********************************************************************* + + formats/atom_tap.c + + Cassette code for Acorn Atom tap files (Kansas City Standard) + +*********************************************************************/ + +/* + + http://beebwiki.jonripley.com/Acorn_cassette_format#Atom + + The Atom supports the System series format (as a 'nameless file') and its own format. The data consists of files separated + by carrier breaks and the appropriate leaders and trailers, and further subdivided into blocks separated by inter-block gaps. + An Atom block consists of the following sequence of bytes: + + Four synchronisation bytes (&2A). + File name (one to thirteen characters). + One end of file name marker byte (&0D). + Block flag, one byte. + Block number, two bytes, high byte first. + Data block length ? 1, one byte. + Execution address, two bytes, high byte first. + Load address, two bytes, high byte first. + Data, 0 to 256 bytes. + Checksum, one byte. + + The block flag is set as follows: + + Bit 7 is set if this block is not the last block of a file. + Bit 6 is set if the block contains data. If clear then the 'data block length' field is invalid. + Bit 5 is set if this block is not the first block of a file. + Bits 4 to 0 are undefined. Normally their contents are: + in the first block, bits 15 to 11 of the end address (=1 + the last address saved in the file); + in subsequent blocks, bits 6 to 2 of the previous block flag. + + The checksum is a simple sum (modulo 256) of all bytes from the start of the filename to the end of the data. + +*/ + +#include <assert.h> + +#include "atom_tap.h" +#include "uef_cas.h" +/*************************************************************************** + PARAMETERS +***************************************************************************/ + +#define LOG 1 + +/*************************************************************************** + IMPLEMENTATION +***************************************************************************/ + +/*------------------------------------------------- + CassetteModulation atom_tap_modulation +-------------------------------------------------*/ + +static const struct CassetteModulation atom_tap_modulation = +{ + CASSETTE_MODULATION_SINEWAVE, + 1200.0 - 300, 1200.0, 1200.0 + 300, + 2400.0 - 600, 2400.0, 2400.0 + 600 +}; + +/*------------------------------------------------- + cassette_image_read_uint8 - read tape data +-------------------------------------------------*/ + +static UINT8 cassette_image_read_uint8(cassette_image *cassette, UINT64 offset) +{ + UINT8 data; + cassette_image_read(cassette, &data, offset, 1); + return data; +} + +/*------------------------------------------------- + atom_tap_identify - identify cassette +-------------------------------------------------*/ + +static casserr_t atom_tap_identify(cassette_image *cassette, struct CassetteOptions *opts) +{ + return cassette_modulation_identify( cassette, &atom_tap_modulation, opts); +} + +/*------------------------------------------------- + atom_tap_load - load cassette +-------------------------------------------------*/ + +#define MODULATE(_value) \ + for (int i = 0; i < (_value ? 8 : 4); i++) { \ + err = cassette_put_modulated_data_bit(cassette, 0, time_index, _value, &atom_tap_modulation, &time_displacement);\ + if (err) return err;\ + time_index += time_displacement;\ + } + +#define BIT(x,n) (((x)>>(n))&1) + +static casserr_t atom_tap_load(cassette_image *cassette) +{ + casserr_t err; + UINT64 image_size = cassette_image_size(cassette); + UINT64 image_pos = 0; + double time_index = 0.0; + double time_displacement; + + while (image_pos < image_size) + { + UINT8 data = cassette_image_read_uint8(cassette, image_pos); + + /* start bit */ + MODULATE(0); + + /* data bits */ + for (int bit = 0; bit < 8; bit++) + { + MODULATE(BIT(data, bit)); + } + + /* stop bits */ + MODULATE(1); + MODULATE(1); + + image_pos++; + } + + return CASSETTE_ERROR_SUCCESS; +} + +/*------------------------------------------------- + CassetteFormat atom_tap_cassette_format +-------------------------------------------------*/ + +const struct CassetteFormat atom_tap_format = +{ + "tap", + atom_tap_identify, + atom_tap_load, + NULL +}; + +CASSETTE_FORMATLIST_START( atom_cassette_formats ) + CASSETTE_FORMAT(atom_tap_format) + CASSETTE_FORMAT(uef_cassette_format) +CASSETTE_FORMATLIST_END |