plip2slip | small AVR transforms a PLIP stream

plip2slip is a C library typically used in Internet of Things (IoT), Arduino applications. plip2slip has no bugs, it has no vulnerabilities, it has a Strong Copyleft License and it has low support. You can download it from GitHub.

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.