Hypothesis: SKC++ doesn’t need semaphores. If you disagree with this, please comment, with supporting arguments. In the meantime, I’ll present a few arguments of my own, Read more…
When it comes to interrupts, SKC++’s guiding principle is “minimum interference”.
Some kernels require that interrupts be processed internally, the internal Interrupt Service Routine (ISR) calling out to an ordinary user function, sometimes also called an ISR, confusingly. Some others let you code the ISR yourself but impose restrictions on how you do it.
SKC++ does not require you to alter the way you program ISRs; Read more…
Just a short article today as SKC++’s mutual exclusion facilities follow a familiar pattern Read more…
Although I separated the ideas of posting an untrammelled event, using post, and sending a message (which also posts an event), using send, this is not such a good idea for receiving messages. One of the key things about an SKC++ task is that it should be able to wait at a single point in its processing in order to get something to process and that it should deal with only one event or message at a time. Accordingly, the wait function has been enhanced to deal with message reception, as well as with raw events. Read more…
I have simplified the prototype for send in order to make its use a little easier and also to improve the efficiency of the implementation. Here is the new prototype: Read more…
This is a relatively short article, as the sending of messages from one task to another is straightforward. I decided to defer its counterpart, “Receiving Messages”, until next time because there are several things to consider there, making the subject worthy of an article of its own. Read more…
To avoid clutter, I haven’t shown the class methods. On this occasion, I’ll just describe the classes and their characteristics in the text. Read more…
Before jumping into the design of the message-passing classes, it is as well to consider how the facility might be used in applications.
I start with a common, nicely encapsulated but rather restricted kind of use…
In this slightly abused UML activity diagram we see Read more…
Message-passing is used, in an RTOS-based system, to provide a safe way of transferring data from one context to another or, in other words, from task to task. What is safe, though, is not always efficient and vice versa. Read more…
I’ve been looking over my SKC++ postings so far and have come to the conclusion that it’s time for a review. Also, before launching into the details of the kernel’s message-passing techniques, I need to show why message-passing is needed in the first place. I’ll start by presenting some thoughts on the tasking model. Read more…