XD-2031 - Serial line filesystem server for CBMs
------------------------------------------------
V0.9.x, Feb 2022

NOTE: This software is in the middle of a re-org. Wear your hard hat

This software enables to program an AVR AtMega device to play
the role of a disk drive to a Commodore PET computer with IEEE488 
interface, a disk drive for the serial-IEC-based machines like
the C64, the C128 and others.

XD-2031 consists of two main parts, an AtMega firmware, and a PC server.
Both communicate via a serial line. 

Currently this hardware is supported:
	- XS-1541 	Communication via serial line over USB
	- petSD   	Communication via serial line over USB
	- petSD2   	Communication via serial line over USB

For more information see the README files in the subdirectories


Building
--------

To build the firmware image, see the README file in the firmware directory.
To build the server side code, see the README file in the pcserver directory.


Testing
-------

To build the tests, simply run "make tests" in this directory.
Please note that the (growing) number of tests has some that fail - that
is partly due to sampling test data from a CBM DOS, that is buggy itself
(like the blkaf1/blkaf2 tests do not allocate blocks on disk on the 4040
emulation...)


Using
-----

To use the PC as disk drive, the Commodore must be connected to one
of the supported devices running the firmware part. This device must
be connected to the PC, usually with a serial-over-USB connection.
The server can then be configured with some command line options:

	-d <devicepath>
		path to the serial device where the server communicates
		with the firmware

	-A<drv>:<provider-string>
		This "assign" command allows defining what is behind
		a "drive" in Commodore terms. The code allows for using
		ten different drive numbers (as opposed to the common
		two), so you can have drive numbers 0-9. 
		The provider-string is special in that it defined what
		is then used as drive content. It consists of a provider
		name, and a parameter string for the provider.
		A provider can be "fs" for the local file system,
		"tcp" for a TCP/IP connection, or "ftp" or "http" for
		their respective protocols. Here are examples and 
		descriptions of their parameters:

		fs=<directory-path>
			assigns a local directory to a drive
		tcp=<hostname>
			assigns a host name to a drive, any OPEN
			then opens the port given as OPEN file name
		ftp=<hostname>[/<path>]
		http=<hostname>[/<path>]
			assigns an FTP or HTTP path to the drive.
			Only FTP supports reading a directory though.

	-X<bus>:<cmd>
               send an 'X'-command to the specified bus, e.g. to set
               the IEC bus to device number 9 use:

	               -Xiec:U=9
	
		"<bus>" can normally be "iec" or "ieee" (or "sock488" for the
		socket-based test version of the firmware".
		Another interesting commands are 

			-X<bus>:*=+
				enable the use of advanced wildcards
			-X<bus>:*=-
				disable the use of advanced wildcards

			-X<bus>:E=-
			-X<bus>:E=+
				disable/enable the drive number if the channel 15
				error messages, also restrict number of 
				digits for track and sector to two
			-XR
				Reset the device
			
		If the device as non-volatile configuration memory, these commands
		are also available:

			-XI
				restore default values from NV-RAM
			-XW
				write configuration to NV-RAM


Please note that you can use the X and A commands also on the command channel, from the
Commodore machine side.

	OPEN15,8,15,"A9:fs=foodir"

	or

	PRINT#15,"XU=9"

You can leave out the bus here, as the command is given to the bus that receives the
command.


Notes
-----

- With the XS1541 hardware all hardware attached to the device on the bus
  you want to use must be switched on on reset. I.e. if you want to use the
  IEEE bus, all IEEE devices must be switched on, the same holds for the IEC
  bus. You can switch on the devices on the other bus later, but if you switch
  a device off, the device hangs. This is due to the switched off devices
  pulling down the ATN line, blocking the XS1541
  


Copyright
---------

The code is under GPL V2. Please note that the PC server part is
also available on later versions of the GPL, the AtMega firmware is
ONLY(!) available under GPL V2.

(C) 2012,2014 Andre Fachat <[email protected]>,
	 Ingo Korb, Thomas Winkler, Nils Eilers and others!

Please see the individual files for specific copyright notices.



ROADMAP
--------

Here are some ideas about what can be implemented. For and more current
information see also the github issues list on:
https://github.com/fachat/XD2031/issues?state=open


Planned features for Release 1.0
--------------------------------

- direct channel support (U1/U2 commands)
	-> done
- SD card provider on the atmega side
	-> started
- D64 support on the server side, to be able to use D64/D80/D82 etc files
	-> done
- IEC support so C64 et al can use the device 
	-> done for C64, done for C128,
	   and VIC20 still to test
- Use other providers without ASSIGN before, e.g. LOAD"sd:filename",8
	-> done (for http/ftp/tcp)
- bidirectional file support, together with TELNET functionality
	-> done
- store configuration parameters in EEPROM
	-> beta
- set configuration parameters from the PC
	-> done
- and various other small improvements


Further plans
-------------

With the ASSIGN command it is possible to assign drive numbers (like the "0" in "$0") 
to different service providers. Some of those will be in the atmega, some will be on the PC side.
Currently there is only one in the atmega, the one that connects via RS232-over-USB. On the PC
side there currently are five, filesystem, disk images, plain TCP as well as FTP and HTTP. 
All those providers basically implement the "wireformat" protocol, so it is a clearly separated 
responsibility. If you are willing to help with one of these ideas, feel free to contact me!

In the future these providers can be implemented:

	- A D64 provider on the atmega side, to use D64/D80/D82 etc files from the SD card
	- An iec provider - so a PET can "call out" to a serial IEC floppy
	- And vice versa, an ieee provider and a serial iec bus interface to
	  allow e.g. the C64 to use an IEEE488 disk
	- A remote FS provider on the PC side: connect to a remote "wireformat" server

On the XS1541 I'm actually willing to sacrifice the parallel user port connector (for C64 fastloaders)
in favour of a device number switch, an SD card interface, and maybe a serial configuration PROM.

Further ideas:

	- support a non-parallel fast loader for the C64 (e.g. Jiffy-DOS?)
        - M-R/W feature to mimic existing drives (to fool copy programs,
          possibly change unit address via M-W)


REFERENCES
----------

XS-1541: The hardware by T. Winkler is described here:
	 http://xd2031.petsd.net/xs1541.php

petSD:   The hardware by N. Eilers is described here:
	 http://petsd.net

sd2iec:	 Some files in this firmware are derived from the sd2iec project by I. Korb
	 http://www.c64-wiki.com/index.php/sd2iec_%28firmware%29

cURL:	 The cURL library is used to implement internet communication, esp.
	 the HTTP and FTP protocols. You can find it at
	 http://curl.haxx.se/