RTL8181 is a system-on-chip device, designed and manufactured by
Realtek Semiconductors.
It embeds:
32-bit Lexra LX5280 core CPU (MIPS clone) with MMU
two 10/100 Ethernet MACs (RTL8139)
one 802.11b wireless MAC (RTL8180)
It also includes a 16550-compatible UART, PCI bridge, 16-port GPIO,
4 general purpose timers, watchdog timer and EJTAG.
The RTL8181 data sheet is available at several locations on the
Internet, see "Online Resources" below.
Development boards?
Plenty. Chances are that you can get one at your local wireless gear retailer.
OK, they may be labelled "Wireless Access Point" or "Wireless
Router", but this is a minor detail with little relevance :)
No kidding. Fact is, most RTL8181-based consumer appliances that we know
about come with a serial port (or at least a MAX232-ready TTL serial header)
and sometimes even a JTAG header. The bundled boot loader supports TFTP
firmware uploads and flash read/write.
Long story short: these devices are readily hackable out of the box.
See the device list for a growing list of
RTL8181-based consumer devices.
Online resources
Related projects and code bits:
the RTL8180-SA2400
project on Sourceforge is developing an open source driver for
stand-alone RTL8180-based cards with Philips SA2400 radio frontend.
the nonmips
project on Sourceforge aims to provide open source tools and support
patches for patent-free MIPS clones, including RTL8181.
Gergely Risko has written
a modding toolkit for linux-based firmware
binaries for X-Micro 11bRRG and other RTL8181 devices.
the Linux-MIPS
project on Sourceforge includes some support for older Lexra CPUs (not LX5280).
Of all manufacturers that are distributing Linux binaries in
violation of the GPL,
only a few are currently making at least some source code available
(a part-open part-closed package from Realtek):
Minitar has older version 1.4 available
here
and a newer version 1.6
here.
MINITAR runs a
web forum board that hosts
some interesting discussions, from the legality of binary-only Linux firmware
to more practical aspects, like AP mods.