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94 lines
3.5 KiB
Markdown
94 lines
3.5 KiB
Markdown
# RC2014
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The [RC2014][rc2014] is a nice and minimal z80 system that has the advantage
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of being available in an assembly kit. Assembling it yourself involves quite a
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bit of soldering due to the bus system. However, one very nice upside of that
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bus system is that each component is isolated and simple.
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The machine used in this recipe is the "Classic" RC2014 with an 8k ROM module
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, 32k of RAM, a 7.3728Mhz clock and a serial I/O.
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The ROM module being supplied in the assembly kit is an EPROM, not EEPROM, so
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you can't install Collapse OS on it. You'll have to supply your own.
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There are many options around to boot arbitrary sources. What was used in this
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recipe was a AT28C64B EEPROM module. I chose it because it's compatible with
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the 8k ROM module which is very convenient. If you do the same, however, don't
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forget to set the A14 jumper to high because what is the A14 pin on the AT27
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ROM module is the WE pin on the AT28! Setting the jumper high will keep is
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disabled.
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## Related recipes
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This recipe is for installing a minimal Collapse OS system on the RC2014. There
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are other recipes related to the RC2014:
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* [Writing to a AT28 from Collapse OS](eeprom/README.md)
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* [Accessing a MicroSD card](sdcard/README.md)
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* [Self-hosting](selfhost/README.md)
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* [Interfacing a PS/2 keyboard](ps2/README.md)
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## Recipe
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The goal is to have the shell running and accessible through the Serial I/O.
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You'll need specialized tools to write data to the AT28 EEPROM. There seems to
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be many devices around made to write in flash and EEPROM modules, but being in
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a "understand everything" mindset, I [built my own][romwrite]. This is the
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device I use in this recipe.
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### Gathering parts
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* A "classic" RC2014 with Serial I/O
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* [Forth's stage binary][stage]
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* [romwrite][romwrite] and its specified dependencies
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* [GNU screen][screen]
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* A FTDI-to-TTL cable to connect to the Serial I/O module
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### Build the binary
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Building the binary is as simple as running `make`. This will yield `os.bin`
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which can then be written to EEPROM.
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This build is controlled by the `xcomp.fs` unit, which loads `blk/618`. That's
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what you need to modify if you want to customize your build (if you do, you'll
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need to rebuild `/emul/stage` because the blkfs is embedded in it).
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### Emulate
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The Collapse OS project includes a RC2014 emulator suitable for this image.
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You can invoke it with `make emul`. See `emul/hw/rc2014/README.md` for details.
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### Write to the ROM
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Plug your romwrite atmega328 to your computer and identify the tty bound to it.
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In my case (arduino uno), it's `/dev/ttyACM0`. Then:
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screen /dev/ttyACM0 9600
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CTRL-A + ":quit"
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cat rom.bin | pv -L 10 > /dev/ttyACM0
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See romwrite's README for details about these commands.
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Note that this method is slow and clunky, but before long, you won't be using
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it anymore. Writing to an EEPROM is much easier and faster from a RC2014
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running Collapse OS, so once you have that first Collapse OS ROM, you'll be
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much better equipped for further toying around (unless, of course, you already
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had tools to write to EEPROM. In which case, you'll be ignoring this section
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altogether).
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### Running
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Put the AT28 in the ROM module, don't forget to set the A14 jumper high, then
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power the thing up. Connect the FTDI-to-TTL cable to the Serial I/O module and
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identify the tty bound to it (in my case, `/dev/ttyUSB0`). Then:
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screen /dev/ttyUSB0 115200
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Press the reset button on the RC2014 and the "ok" prompt should appear.
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[rc2014]: https://rc2014.co.uk
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[romwrite]: https://github.com/hsoft/romwrite
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[stage]: ../../emul
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[screen]: https://www.gnu.org/software/screen/
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