μみゅーClinux

μみゅーClinux is a variation of the Linux kernel, previously maintained as a fork, that targets microcontrollers without a memory management unit (MMU). It was integrated into the mainline kernel as of 2.5.46; the project continues to develop patches and tools for microcontrollers. The homepage lists Linux kernel releases for 2.0, 2.4 and 2.6 (all of which are end-of-life in mainline).

μみゅーClinux

An iPod booting iPodLinux, based on μみゅーClinux
OS family	Embedded Linux
Working state	Current
Source model	Open source
Platforms	See below
Kernel type	Linux kernel-fork
Userland	uClinux-dist, uClibc, BusyBox
Official website	uclinux.org at the Wayback Machine (archived 2018-11-13)

uClibc is a wrapper around the system calls of the Linux kernel and/or μみゅーClinux.

The letters "μみゅーC" are for "microcontroller": the name is pronounced "you-see-Linux", rather than pronouncing the letter mu as in Greek.

History

μみゅーClinux was originally created by D. Jeff Dionne and Kenneth Albanowski in 1998. Initially, they targeted the Motorola DragonBall family of embedded 68k processors (specifically the 68EZ328 series used in the 3Com PalmPilot) on a 2.0.33 Linux kernel. After releasing their initial work, a developer community quickly sprang up extending their work to newer kernels and other microprocessor architectures. In early 1999, support was added for the Motorola (now NXP) ColdFire family of embedded microprocessors. ARM processor support was added later.

Although originally targeting 2.0 series Linux kernels, it now has ports based on Linux 2.4 and Linux 2.6. The Linux 2.4 ports were forward ported from the 2.0.36 Linux kernel by Michael Leslie and Evan Stawnyczy during their work at Rt-Control. There were never any μみゅーClinux extensions applied to the 2.2 series kernels.

Since version 2.5.46 of the Linux kernel, the major parts of μみゅーClinux have been integrated with the mainline kernel for a number of processor architectures.

Greg Ungerer (who originally ported μみゅーClinux to the Motorola ColdFire family of processors) continued to maintain and actively push core μみゅーClinux support into the 2.6 series Linux kernels. In this regard, μみゅーClinux is essentially no longer a separate fork of Linux.

μみゅーClinux had support for many architectures, and forms the basis of many products, like network routers, security cameras, DVD or MP3 players, VoIP phone or gateways, scanners, and card readers.

Support for several of the original target architectures was dropped in 2018. The obsolete CPU architectures set to be removed in Linux 4.17 and subsequent releases included ADI Blackfin, Etrax CRIS, Fujitsu FR-V, Mitsubishi M32R, Matsushita/Panasonic MN10300, Imagination META (Metag), and Tilera TILE.

Hardware projects

The leanXCam was an open-source programmable smart camera used for industrial applications in the field of machine vision that ran under μみゅーClinux; the camera won an award at the 2008 VISION tradeshow. As of 2015, the project was discontinued.

Supported architectures

The current list includes:

• Altera Nios/Nios II
• Amber (open FPGA core)
• ARM ARM7TDMI, ARM Cortex-M3/M4/M7, ARM Cortex-R
• Lattice Mico32
• NXP 680x0 (Motorola/Freescale 680x0)
• Hyperstone E1/E2 (called hyLinux)
• Intel i960
• MIPS
• NXP ColdFire (Motorola/Freescale ColdFire)
• Xilinx MicroBlaze

No longer supported

• NEC V850E - removed in Linux 2.6.27.
• Hitachi/Renesas H8 (h8300) - removed in Linux 5.19.

Before Linux 4.17 the following architectures were also supported:

• ADI Blackfin (blackfin)
• Axis ETRAX (cris)
• Fujitsu FR-V (frv)
• Mitsubishi/Renesas M32R (m32r)

External links

• Uclinux-dev on GitHub
• μみゅーClinux-dist, complete source distribution package at the Wayback Machine (archived 2018-11-13)
• μみゅーClinux at SourceForge
• μみゅーClinux - Setting up the Development Environment at the Wayback Machine (archived 2017-03-24)
• Accelerated Linux, an actively developed continuation of μみゅーClinux-dist by Digi