The ITRON[1] project was the first sub-project of the TRON project.[2] It has formulated and defined Industrial TRON (ITRON) specification for an embedded real-time OS (RTOS) kernel.
Originally undertaken in 1984, ITRON is a Japanese open standard for a real-time operating system initiated under the guidance of Ken Sakamura. This project aims to standardize the RTOS and related specifications for embedded systems, particularly small-scale embedded systems. The ITRON RTOS specification is targeted for consumer electronic devices, such as mobile phones and fax machines. Various vendors sell their own implementations of the RTOS.
ITRON, and μITRON (sometimes also spelled uITRON or microITRON) are the names of RTOS specifications derived from ITRON projects. The 'μ' character indicates that the particular specification is meant for the smaller 8-bit or 16-bit CPU targets. Specifications are available for free. Commercial implementations are available, and offered under many different licenses.
A few sample source implementations of ITRON specification exist, as do many commercial source offerings.
Examples of open source RTOSes incorporating an API based on μITRON specification are eCos and RTEMS.
ITRON specification is meant for hard real-time embedded RTOS.
It is very popular in the embedded market, as there are many applications for it, i.e., devices with the OS embedded inside.
For example, there is an ACM Queue interview with Jim Ready, founder of MontaVista (realtime linux company), "Interview with Jim Reddy", April 2003, ACM Queue.[3] He says in the interview, "The single, most successful RTOS in Japan historically is μITRON. This is an indigenous open specification led by Dr. Ken Sakamura of the University of Tokyo. It is an industry standard there." Many Japanese digital cameras, for example, have use ITRON specification OS. Toyota automobile has used ITRON specification OS for engine control.
According to the "Survey Report on Embedded Real-time OS Usage Trends" conducted every year by TRON Forum at the Embedded Technology (ET, organized by Japan Embedded Systems Technology Association: JASA), ITRON specification OS has long held the top share in the embedded OS market in Japan and is adopted as the industry standard OS. For example, in the FY 2016 survey,[4] TRON OSs (including ITRON specification OS and T-Kernel) accounted for around 60% of the embedded systems market. ITRON specification OSs (including μITRON) alone accounted for 43% of the market, and had a 20% lead over UNIX-based OSs (including POSIX), which are in second place behind TRON OSs.
Although ITRON specification may not be very well known overseas, OSs that conform to it have been installed in Japanese-made home appliances and exported around the world, so ITRON specification OS has a high market share. As of 2003, it was ranked number one in the world in terms of OS market share.[5] Because its license could be easily obtained and it was free, it was used quite a bit in Asia.
μITRON (read as micro ITRON, not "mu" ITRON) specification started out as a subset of the original ITRON specification. However, after the version 3 of the μITRON specification appeared, since it covers both the low-end CPU market as well as large-scale systems, the term ITRON often refers to μITRON.
Supported CPUs are numerous. ARM, MIPS, x86, SH FR-V and many others including CPUs supported by open source RTOS eCos and RTEMS, both of which include the support for μITRON compatible APIs.
TRON Project began designing the computer architecture as an infrastructure of the future computer applications, and presented an overview of the basic design at the 29th National Convention of the Information Processing Society of Japan in 1984.