plip2slip
=========

"Build a PLIP-to-SLIP HW Bridge device using an Arduino board for speeding up
Internet on a stock Amiga 500."

Copyright (C) 2011 Christian Vogelgsang <chris@vogelgsang.org>

Released under the GNU Public License V2 (see COPYING for details)

Introduction
------------

An Amiga 500 has no special ethernet or other network ports for connecting to
the Internet. Typically a SLIP (serial line internet protocol) device is used
to transfer all IP packets via the serial RS 232 interface to another computer
with fast ethernet connection. With the on-board serial port a maximum speed
of 9600 Baud (~ 1 KiB/s) could be achieved running Amiga OS.

Faster speeds could be achieved by using a PLIP (parallel port IP) device that
uses the parallel port to transfer IP packets to another host. Since the Amiga
parallel port is fully bi-directional you can use a half-duplex protocol and
then transfer an IP packet byte-by-byte over the port. This is done in the
magPLIP driver available on Aminet[1]. Unfortunately, this approach requires
an Amiga or another Computer with a fully bi-directional port on the peer side.
With this parallel approach you can achieve up to 15-20 KiB/s transfer speeds.

The idea in this project is to use the custom I/O ports of an AVR microcontroller
board (here an Arduino 2009) and implement the parallel port there. The mcu
implements the magPLIP protocol and can then receive and send packets to/from
the Amiga.

On the other hand, the Arduino uses an FTDI 232 USB-to-Serial bridge to allow
fast serial data transfers. On a 16 MHz AVR you can use serial rates up to 500
KiBit/s (~ 55 KiB/s). With proper RTS/CTS flow control the AVR can handle
these data rates easily.

The "plip2slip" firmware developed in this project now bridges these two
ports. A PC is connected with a fast serial link to the AVR and the Amiga is
connected with its parallel port. As a result the amiga can achieve full PLIP
speed while the PC runs a fast SLIP link.

On the PC I use Linux with a patched slattach tool to support the fast serial
rates. The Amiga magPLIP device is slightly patched to better support the AVR.
All patches are available in this project.

The data flow is as follows:

Internet <->   PC   <--SLIP-->  Arduino  <--PLIP-->  Amiga 500
              Linux            plip2slip            magPLIP + AmiTCP

[1] http://aminet.net/package/comm/net/magPLIP38.1


plip2slip Documentation
-----------------------

 doc/hardware.txt               How to build the device hardware
 doc/terminal.txt               How to setup a serial terminal for command mode
 contrib/magplip/README         How to install the AMIGA network module
 contrib/slattach/README        How to patch and setup SLIP on Linux