source: buchla-emu/readme.txt@ 3153af3

0.1
Last change on this file since 3153af3 was 6027d76, checked in by Thomas Lopatic <thomas@…>, 6 years ago

Get rid of ttf subdirectory.

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1Buchla 700 Hardware Emulator
2----------------------------
3
4This repository, buchla-emu.git, contains a software emulation of the
5Buchla 700's hardware.
6
7It is minimalistic; it emulates just enough of the hardware to be able
8to run the firmware from the companion repository, buchla-68k.git.
9
10We don't have access to original hardware, so this is our best guess
11based on the firmware source code published by Lynx Crowe - the
12firmware's developer - via Aaron Lanterman:
13
14 http://lanterman.ece.gatech.edu/buchla700/
15
16See the buchla-68k.git repository for the firmware source code.
17
18
19Building the emulator
20---------------------
21
22The emulator uses SDL2, an abstraction layer for low-level machine
23access on Linux, OS X, and Windows. It can be obtained from the
24project's website:
25
26 https://libsdl.org/
27
28The SDL2 website also hosts the SDL2_net and SDL2_ttf projects, which
29add support for networking and TrueType fonts to SDL2
30
31SDL2_ttf, in turn, requires the FreeType library, which is available
32from the FreeType website:
33
34 https://www.freetype.org/
35
36Currently, we build the emulator natively on Linux and OS X. The
37Windows version is cross-compiled on Linux using a x86_64-w64-mingw32
38cross-toolchain.
39
40For Linux and OS X, our Makefile expects all of the above libraries to
41reside in /opt/sdl2. This is how we typically install them:
42
43 # Build and install FreeType first
44
45 tar zxvf freetype-2.7.1.tar.gz
46 cd freetype-2.7.1
47 mkdir build
48 cd build
49
50 # Skip the optional features (compressed fonts, etc.) that would
51 # create more dependencies
52
53 ../configure --prefix=/opt/sdl2 \
54 --without-zlib --without-bzip2 --without-png --without-harfbuzz
55
56 make
57 make install
58
59 # Then build and install SDL2
60
61 tar zxvf SDL2-2.0.5.tar.gz
62 cd SDL2-2.0.5
63 mkdir build
64 cd build
65
66 ../configure --prefix=/opt/sdl2
67
68 make
69 make install
70
71 # Build and install SDL2_ttf, now that we have FreeType and SDL2
72
73 tar zxvf SDL2_ttf-2.0.14.tar.gz
74 cd SDL2_ttf-2.0.14
75 mkdir build
76 cd build
77
78 ../configure --prefix=/opt/sdl2 \
79 --with-sdl-prefix=/opt/sdl2 --with-freetype-prefix=/opt/sdl2
80
81 make
82 make install
83
84 # Build and install SDL2_net last
85
86 tar zxvf SDL2_net-2.0.1.tar.gz
87 cd SDL2_net-2.0.1
88 mkdir build
89 cd build
90
91 ../configure --prefix=/opt/sdl2 --with-sdl-prefix=/opt/sdl2
92
93 make
94 make install
95
96 # Build and install RtMidi
97
98 tar zxvf rtmidi-3.0.0.tar.gz
99 cd rtmidi-3.0.0
100 mkdir build
101 cd build
102
103 ../configure --prefix=/opt/rtmidi
104
105 make
106 make install
107
108Now that we have everything in place, invoke
109
110 make buchla
111
112from the top-level directory of this repository to build the emulator.
113
114The cross-build for Windows is done similarly, with the following
115differences when configuring the libraries:
116
117 * We use "--prefix=/opt/sdl2-win" instead of "--prefix=/opt/sdl2",
118 so that the Windows versions of the SDL2 libraries go to a
119 different directory. That's where our Makefile expects to find
120 them when cross-building.
121
122 Analogously, we use "--prefix=/opt/rtmidi-win" when building
123 RtMidi.
124
125 * We additionally specify "--host=x86_64-w64-mingw32" to enable
126 cross-compilation.
127
128Then, to cross-build the emulator, invoke
129
130 make buchla.exe WIN=1
131
132from the top-level directory of this repository. Defining the "WIN"
133variable selects the cross-toolchain and "/opt/sdl2-win" as the
134library directory.
135
136In addition to the emulator, we need to build the mkdisk utility,
137which we'll use to create a 720-KiB floppy disk image that can be read
138by the Buchla firmware.
139
140Building mkdisk works pretty much like building the emulator. On Linux
141and OS X, invoke
142
143 make mkdisk
144
145from the top-level directory of this repository. To cross-build the
146Windows version, invoke
147
148 make mkdisk.exe WIN=1
149
150instead.
151
152
153Running the emulator
154--------------------
155
156This is where this repository, buchla-emu, meets its companion
157repository, buchla-68k. We assume that you built the following files
158according to the instructions in the buchla-68k repository:
159
160 bios.abs
161 midas.abs
162
163Please copy (or symlink) them into the top-level directory of this
164repository, buchla-emu.
165
166bios.abs contains the Buchla 700's BIOS code. The file is loaded by
167the emulator directly to emulate the BIOS PROM.
168
169midas.abs is the MIDAS VII software. Unlike the BIOS, which resides in
170a PROM, it is loaded from a floppy disk. To create this floppy disk,
171we need the mkdisk utility.
172
173mkdisk expects to be run from inside the directory that contains
174midas.abs and produces a disk image file, buchla.disk in the same
175directory. For example, on Linux:
176
177 ~/buchla-emu$ ls -l midas.abs
178 lrwxrwxrwx 1 emu emu 23 Jul 30 18:07 midas.abs -> ../buchla-68k/midas.abs
179 ~/buchla-emu$ ./mkdisk
180 ~/buchla-emu$ ls -l buchla.disk
181 -rw-r--r-- 1 emu emu 737280 Aug 6 09:44 buchla.disk
182
183Now we have everything in place to run the emulator. On Linux and OS X
184you can invoke it directly from the top-level directory of this
185repository:
186
187 ~/buchla-emu$ ./buchla
188
189If you prefer to install the emulator elsewhere, be sure to copy the
190following files:
191
192 buchla | buchla.exe emulator executable (.exe for Windows)
193 vera.ttf emulator font
194 bios.abs BIOS code
195 buchla.disk disk image
196
197This also applies to copying the cross-compiled Windows emulator to a
198Windows machine.
199
200If you would like to keep the BIOS code, disk image, and font separate
201from the emulator executable, check out the emulator's -b, -d, and -f
202command line options. Use -h for an overview of all available options.
203
204
205Cross-debugging the firmware
206----------------------------
207
208While the emulator is running, it listens on TCP port 12053 for
209incoming connections from a GDB cross-debugger. This allows for
210comfortable source-level debugging of the cross-compiled BIOS and
211MIDAS VII code, while it runs in the emulator.
212
213We assume that you have a GCC cross-toolchain in /opt/cross-m68k, as
214described in the buchla-68k repository. Based on that, we build a
215GDB cross-debugger:
216
217 # If you haven't yet done so, add the cross-toolchain to your
218 # PATH, so that the GDB build can find it.
219
220 export PATH="/opt/cross-m68k/bin:${PATH}"
221
222 tar zxvf gdb-7.12.tar.gz
223 cd gdb-7.12
224
225 mkdir build
226 cd build
227
228 ../configure --prefix=/opt/cross-m68k --target=m68k-none-elf
229
230 make -j2
231 make install
232
233The Buchla firmware uses its own (Atari-like) object and executable
234file format. However, the cross-toolchain and the cross-debugger
235support the ELF standard.
236
237When you built the BIOS and MIDAS VII software, you ended up with two
238files in the Buchla's executable file format, bios.abs and midas.abs.
239However, the cross-build process also produces matching ELF files,
240bios.elf and midas.elf, suitable for the cross-debugger.
241
242Depending on whether you would like to cross-debug the BIOS or MIDAS
243VII, you'd specify either bios.elf or midas.elf when invoking the
244cross-debugger.
245
246To follow along the following example, copy (or symlink) bios.elf and
247midas.elf from the buchla-68k repository into the top-level directory
248of this repository.
249
250In order to open a debug session for the BIOS, run the cross-debugger
251with bios.abs and connect it to the running emulator using GDB's
252
253 target remote :12053
254
255command. 12053 is the port on which the emulator listens for incoming
256GDB connections.
257
258 host:~/buchla-emu$ m68k-none-elf-gdb ./bios.elf
259 GNU gdb (GDB) 7.12
260 Copyright (C) 2016 Free Software Foundation, Inc.
261 [...]
262 (gdb) target remote :12053
263 Remote debugging using :12053
264 trwzsup () at rom/bios.s:832
265 832 move.l 0(a0,d0),d0 | Get routine address
266 (gdb)
267
268From here on, everything is pretty much standard GDB, for example:
269
270 (gdb) break pscan
271 Breakpoint 1 at 0x105a64: file rom/romp.c, line 3403.
272 (gdb) cont
273 [...]
274 (gdb) bt
275 #0 pscan () at rom/romp.c:3403
276 #1 0x00105e96 in main () at rom/romp.c:3587
277 #2 0x00105fd6 in Croot (cp=0x0) at prolog/croot.c:141
278 #3 0x00105f52 in start1 () at prolog/fsmain.s:59
279 (gdb)
280
281In order to debug MIDAS VII, run the cross-debugger with midas.elf,
282instead:
283
284 host:~/buchla-emu$ m68k-none-elf-gdb ./midas.elf
285 GNU gdb (GDB) 7.12
286 Copyright (C) 2016 Free Software Foundation, Inc.
287 [...]
288
289
290Emulated hardware
291-----------------
292
293Here's what we currently emulate:
294
295 * Motorola 68000 CPU. This is actually the Musashi CPU emulator by
296 Karl Stenerud:
297
298 https://github.com/kstenerud/Musashi
299
300 * Intel 82716: Video chip.
301
302 * Epson SED1335: LCD controller.
303
304 * Western Digital WD1772: Floppy disk controller.
305
306 * Rockwell R65C52: Serial console and MIDI ports.
307
308 * Motorola MC6840: Timers.
309
310 * Unknown item #1: A program running on a microcontroller. It
311 converts the analog signals from the Buchla's controller pads to
312 digital values.
313
314 Neither the program, nor the microcontroller are known, but the
315 protocol (known from the firmware source code) is pretty simple
316 and self-explanatory.
317
318The next development milestone will hopefully emulate the following
319additional components:
320
321 * National Semiconductor LMC835: Equalizer.
322
323 * General Instrument AY-3-8910: A sound chip, which is not used for
324 sound generation, but only for its I/O ports. It connects the CPU
325 to the above equalizer chip.
326
327 * A few indicator LEDs.
328
329 * Unknown item #2: The actual sound generator, referred to by the
330 firmware source code as "the FPU." This is the biggest unknown so
331 far. Judging from the firmware source code it consist of two
332 parts:
333
334 1. The function generator that generates the 15 different
335 parameter envelopes for each of the 12 voices:
336
337 - 4x FM modulator (oscillator) frequency.
338
339 - 6x FM modulator (oscillator) envelope.
340
341 - 1x Output signal amplitude envelope.
342
343 - 1x Output signal filter envelope.
344
345 - 1x Output signal filter resonance envelope.
346
347 - 1x Output signal stereo location.
348
349 - 1x "Dynamics" - whatever that is.
350
351 The firmware feeds the the points of the envelopes drawn in
352 the MIDAS VII instrument editor to the function generator,
353 which then interpolates between them.
354
355 2. The digital oscillator.
356
357 XXX - Details to be filled in.
358
359 We don't know how many of the envelopes not related to FM
360 (e.g., the filter) are actually used digitally. At least some
361 of the envelopes probably control analog circuits.
362
363 This "two FPU parts" hypothesis would be in line with the "four
364 computers" marketing claim from the Buchla 700 marketing copy. The
365 four "computers" would be the Motorola 68000, the microcontroller
366 that does the A/D conversion of the pad inputs, plus the two parts
367 that constitute "the FPU."
368
369 The firmware source code archive indicates that the FPU is based
370 on micro-programmable hardware. We recently ran this by Lynx, the
371 developer of the firmware, who generously agreed to meet up with
372 us in Oakland, CA. While he did not work on the FPU and thus was
373 not familiar with its implementation details, he was able to
374 confirm that the FPU is based on AMD's Am2900 family.
375
376If you have access to an actual Buchla 700, please do contact us. It
377would be great to be able to compare the emulation to real hardware.
378
379If your Buchla is non-functional, this is also fine. We might be able
380to gain some insights from reading out the FPU microcode PROMs or from
381figuring out how the FPU chips are wired together.
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