From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: STM32F4 Discovery, communication and libraries Date: Thu, 28 Aug 2014 22:09:05 +0200 Organization: cbb software GmbH Message-ID: References: <60a42dc6-d8d0-4432-ae5a-86de18b82840@googlegroups.com> <5kkrv9hejn2qhdckkeo8lidkbh3bkme1gn@4ax.com> <5b91313c-acf9-4a6e-b157-6ba7c8021567@googlegroups.com> <0513ad07-6fbe-463a-be6f-097cd5113f52@googlegroups.com> <4f1ec65a-d66a-40bf-a0d6-278fde206e70@googlegroups.com> Reply-To: mailbox@dmitry-kazakov.de NNTP-Posting-Host: etnUhctbDQ6U1zAlbX4CBw.user.speranza.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: 40tude_Dialog/2.0.15.1 X-Notice: Filtered by postfilter v. 0.8.2 Xref: news.eternal-september.org comp.lang.ada:21964 Date: 2014-08-28T22:09:05+02:00 List-Id: On Thu, 28 Aug 2014 09:28:15 -0700 (PDT), Mike Silva wrote: > On Thursday, August 28, 2014 6:00:12 AM UTC-7, Dmitry A. Kazakov wrote: >> One of the responsibilities of the OS and the middleware is to perform I/O >> on things like ModBus in background without blocking the application and >> other I/O. Even a very lame board is usually much faster than any ModBus >> terminal. > > Maybe there is some confusion being caused by the term "OS" here. Ada's > concurrency and realtime functionality can run on top of an OS, but it can > also run on bare metal (an "invisible" OS?). Not really. OS is more than tasking, it is also a queueing mechanism, which allows waiting for I/O completion in one task without blocking all other tasks. > The GNAT ARM Cortex M > release does have Ravenscar tasking on bare metal. You could not implement an equivalent of I/O queueing under the Ravenscar constraints. >> In short, an OS-less design is not suitable for handling many peripheral >> devices simultaneously, especially when the devices are attached over slow >> asynchronous communication channels. > > How could this be reworded to remove the "OS"? A single-task or > single-thread design is not suitable...? A design without a mechanism of postponing and synchronization to multiple I/O events. The most simple case is when a task can be blocked until the event happens. Alternatively it could be an asynchronous system trap. That is when the task is interrupted upon an I/O event. Such an event-driven schema may deploy single task. It is frequently used in GUI design and is sufficiently more difficult to use. It would still require an OS for switching contexts. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de