mirror of
https://github.com/mist-devel/mist-board.git
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More removal of google code links
Newsdee
@@ -28,7 +28,7 @@ First you have to prepare the SD card. Place the following files in the root dir
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## Atari ST ##
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* [The early Atari ST FPGA core (core.rbf) for boards purchased before May 2015](http://code.google.com/p/mist-board/source/browse/trunk/bin/cores/mist/core.rbf) or
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* [The early Atari ST FPGA core (core.rbf) for boards purchased before May 2015](https://github.com/mist-devel/mist-binaries/blob/master/cores/mist/core.rbf) or
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* [The Atari ST FPGA core for boards purchased May 2015 or later](https://github.com/mist-devel/mist-binaries/blob/master/cores/mist/core_150708_r1202.rbf)
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* [A (Emu-)TOS rom image (tos.img)](https://github.com/mist-devel/mist-binaries/blob/master/cores/mist/tos.img)
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* [A default floppy disk image for drive A:](https://raw.githubusercontent.com/wiki/mist-devel/mist-board/disk_a.st)
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@@ -6,7 +6,7 @@ This document is not for you if you don't know what the minimig is or how to use
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# System overview #
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The original Minimig consists of very few components as depicted above. These are:
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@@ -41,7 +41,7 @@ The microcontroller has direct access to the SD card. This is the only component
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## Stage 3: Preparing kickstart ##
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The FPGA configuration also includes [a minimal 68k code block (bootrom)](http://code.google.com/p/minimig/source/browse/trunk/BOOT68K/boot.asm). The bootrom is overlayed over some of the RAM after FPGA configuration and is executed by the 68k immediately after the FPGA is configured.
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The FPGA configuration also includes [a minimal 68k code block (bootrom)](https://github.com/mist-devel/mist-board/blob/master/cores/minimig/fw/amiga_boot/amiga_boot.asm). The bootrom is overlayed over some of the RAM after FPGA configuration and is executed by the 68k immediately after the FPGA is configured.
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The bootrom has a counterpart in the microcontrollers code. Both parts are communicating via messages sent through the floppy disk read buffer. The bootrom issues disk read accesses for floppy 1. The microcontroller responds with some magic command pattern which it returns instead of actual floppy disk data. These command messages are used to upload the kickstart rom code from sd card into RAM, to display text on the boot screen, to clear memory or to leave the boot
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state and to disable the bootrom.
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@@ -6,7 +6,7 @@ The cores are written in a combination of Verilog and VHDL. A synthesis tool is
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# Compiling #
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The core source code is available from the [MIST svn repository](http://code.google.com/p/mist-board/source/checkout).
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The core source code is available from the [MIST svn repository](https://github.com/mist-devel/mist-board/tree/master/cores).
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To load the project simple open the project file (**.qpf, e.g. core/mist/mist.qpf) in quartus. On the left side under "Flow" select "Compilation". and double click "Compile Design". Depending in the speed of your computer this may take from some minutes up to an hour.**
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@@ -15,7 +15,7 @@ Refer to this page: [How to compile the firmware under Windows](http://ws0.org/c
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# Compiling the source code #
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The firmware source code is available from the [MIST svn repository](http://code.google.com/p/mist-board/source/checkout).
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The firmware source code is available from the [MIST svn repository](https://github.com/mist-devel/mist-firmware).
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Once the compiler is installed a simple `make` in the firmware subdirectory will build the latest firmware.
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2
Midi.md
2
Midi.md
@@ -20,7 +20,7 @@ A video of a synthesizer connected to the MIDI addon board:
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# Redirected MIDI via USB #
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The MIST board has a USB device port (the Micro USB one also used the power the board) which implements a CDC ACM interface. Under windows this shows up as a COM port ([windows driver inf](http://code.google.com/p/mist-board/source/browse/trunk/bin/firmware/mist.inf)). Under Linux or MacOS X similar device file entries are created under /dev without any special driver being required.
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The MIST board has a USB device port (the Micro USB one also used the power the board) which implements a CDC ACM interface. Under windows this shows up as a COM port ([windows driver inf](https://github.com/mist-devel/mist-binaries/blob/master/firmware/mist.inf)). Under Linux or MacOS X similar device file entries are created under /dev without any special driver being required.
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This virtual COM port can be used for various purposes (e.g. debugging or redirecting printer or serial output). This can be selected using the "USB I/O" entry in the System submenu of the OSD. Select "midi" to redirect MIDI output to the CDC ACM interface.
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24
MidiAddon.md
24
MidiAddon.md
@@ -2,33 +2,33 @@
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The MIDI expansion board board adds a physical Atari ST compatible MIDI port to the MIST board.
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The MIDI expansion board connected to a series V1.2 MIST board.
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# Schematic #
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The board implements a simple MIDI compliant current loop. The MIST runs at 3.3V unlike the orifinal Atari ST which ran on 5V. The values of resistors [R1](https://code.google.com/p/mist-board/source/detail?r=1), [R2](https://code.google.com/p/mist-board/source/detail?r=2), [R5](https://code.google.com/p/mist-board/source/detail?r=5) and [R6](https://code.google.com/p/mist-board/source/detail?r=6) reflect this as well as the fact that IC1 is a low voltagle variant.
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The board implements a simple MIDI compliant current loop. The MIST runs at 3.3V unlike the orifinal Atari ST which ran on 5V. The values of resistors R1, R2, R5 and R6 reflect this as well as the fact that IC1 is a low voltagle variant.
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The MIDI expansion board implements MIDI through exactly like the original Atari ST did on Pin 1 and 3 of the MIDI out connector.
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The board connects directly via SV2 to the FPGA expansion connector of the MIST board V1.2 or V1.3.
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[Schematic(PDF)](http://mist-board.googlecode.com/svn/wiki/midi_schematic.pdf)
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[Schematic(PDF)](https://raw.githubusercontent.com/wiki/mist-devel/mist-board/midi_schematic.pdf)
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# Printed Circuit Board #
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The board fits exactly at the left side of a MIST V1.2 or V1.3 (the first series board) board. Previous development boards may also be connected but need some extra wires.
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[Board(PDF)](http://mist-board.googlecode.com/svn/wiki/midi_pcb.pdf)
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[Board(PDF)](https://raw.githubusercontent.com/wiki/mist-devel/mist-board/midi_pcb.pdf)
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The resulting board looks like this:
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# Case mounting #
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@@ -36,7 +36,7 @@ Mounting the MIDI expansion board in the case your MIST came in requires some mi
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Then you need to drill two big holes in the left side of the top case so the MIDI plugs fit nicely and deep enough into the case to make secure contact.
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The resulting setup is very small yet robust.
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@@ -44,17 +44,17 @@ The resulting setup is very small yet robust.
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MIDI was designed when 5V was the voltage being used in computers. Today it's 3.3V and less what most computers use internally. MIDI implementations struggle with this.
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If we have a look at the schematic on this page you'll see the resistors [R1](https://code.google.com/p/mist-board/source/detail?r=1) and [R5](https://code.google.com/p/mist-board/source/detail?r=5) each being 56 ohms and both limiting the current that flows over pins 1 and 3 on connector X1 (MIDI OUT). That's where the board drives external gear.
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If we have a look at the schematic on this page you'll see the resistors R1 and R5 each being 56 ohms and both limiting the current that flows over pins 1 and 3 on connector X1 (MIDI OUT). That's where the board drives external gear.
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The Atari ST was a 5V device and according to http://dev-docs.atariforge.org/files/520ST_Schematic.pdf used 220 Ohms in the same place ([R77](https://code.google.com/p/mist-board/source/detail?r=77) and [R80](https://code.google.com/p/mist-board/source/detail?r=80)).
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The Atari ST was a 5V device and according to http://dev-docs.atariforge.org/files/520ST_Schematic.pdf used 220 Ohms in the same place (R77 and R80).
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On the receiving side there's always a 220 ohms resistor ([R3](https://code.google.com/p/mist-board/source/detail?r=3) on the MIST and [R76](https://code.google.com/p/mist-board/source/detail?r=76) in the Atari ST)
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On the receiving side there's always a 220 ohms resistor (R3 on the MIST and R76 in the Atari ST)
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This limits the current to 5V/3\*220ohms = 7.5mA in short circuit or 5mA if the opto couplers LED on the receiver side drops 1.7V as (5V-1.7V)/3\*220ohms = 5mA. This is what the MIDI standard assumes.
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A diode with a voltage drop of 1.7V is driven by the MIST with (3.3V-1.7V)/(2\*56 + 220) = 4.8mA. This is a difference of 0.2mA and is actually pretty close and should work. But what if your device has a LED with e.g. 2V voltage drop? Then you have 4.5mA with the 5V circuit and 3.9mA on the 3.3V cicruit. The difference is now 0.6mA. So the influence of the voltage drop of receiver LED becomes bigger in the 3.3V circuit.
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It is possible to lower the values of [R1](https://code.google.com/p/mist-board/source/detail?r=1) and [R5](https://code.google.com/p/mist-board/source/detail?r=5) on a MiSTs MIDI add-on board. It's possible to add 100ohms on top of [R1](https://code.google.com/p/mist-board/source/detail?r=1) and [R3](https://code.google.com/p/mist-board/source/detail?r=3). This will effectively lower both resistors to 35 ohms and increase the current to (3.3-1.7)/(2\*35 +220) = 5.5mA with a 1.7V LED or (3.3-2)/(2\*35+220)=4.5mA with a 2V LED.
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It is possible to lower the values of R1 and R5 on a MiSTs MIDI add-on board. It's possible to add 100ohms on top of R1 and R3. This will effectively lower both resistors to 35 ohms and increase the current to (3.3-1.7)/(2\*35 +220) = 5.5mA with a 1.7V LED or (3.3-2)/(2\*35+220)=4.5mA with a 2V LED.
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The additional current shouldn't hurt any device and may help those of your devices that have difficulties with the MIST. It also doesn't hurt the MiST. It can drive that current (a complete MiST draws about 300-400mA). But be aware that this exceed the MIDI specifications!
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