programmer life guidance 101

RTOS 환경에서 워치독 사용하기 현업 골칫거리 중 하나인 WDT에 대해서 알아보려고 합니다. 먼저 그 중요성에 대해서 알아보겠습니다. 우주 환경에 장기간 노출 된 상태에서 센서와 우주선 구성 요소를 테스트하는 NASA 위성 인 Clementine 은 1994 년 1 월 25 일에 발사되었습니다. 몇 줄의 감시 코드가 부족하여 1994 년 5 월 7 일에 임무를 잃었습니다. 클레멘 타인은 달 궤도를 떠나 그녀의 다음 목표 인 지구 근처의 소행성 Geographos로 향했을 때 약 2 개월 연속 달지도를 수행했습니다. 그러나 곧 Clementine의 온보드 컴퓨터 중 하나에서 오작동이 발생하여 NASA가 우주선 작동을 효과적으로 차단하고 추진기 중 하나가 제어되지 않은 상태로 발사되도록했습니다. NASA는..

Memory Block Pools Allocating memory in a fast and deterministic manner is always a challenge in real-time applications. With this in mind, ThreadX provides the ability to create and manage multiple pools of fixed-size memory blocks. Since memory block pools consist of fixed-size blocks, there are never any fragmentation problems. Of course, fragmentation causes behavior that is inherently un-de..

Event Flags Event flags provide a powerful tool for thread synchronization. Each event flag is represented by a single bit. Event flags are arranged in groups of 32. Threads can operate on all 32 event flags in a group at the same time. Events are set by tx_event_flags_set and are retrieved by tx_event_flags_get. Setting event flags is done with a logical AND/OR operation between the current eve..

Mutexes In addition to semaphores, ThreadX also provides a mutex object. A mutex is basically a binary semaphore, which means that only one thread can own a mutex at a time. In addition, the same thread may perform a successful mutex get operation on an owned mutex multiple times, 4,294,967,295 to be exact. There are two operations on the mutex object, namely tx_mutex_get and tx_mutex_put. The g..

Counting Semaphores ThreadX provides 32-bit counting semaphores that range in value between 0 and 4,294,967,295. There are two operations for counting semaphores: tx_semaphore_get and tx_semaphore_put. The get operation decreases the semaphore by one. If the semaphore is 0, the get operation is not successful. The inverse of the get operation is the put operation. It increases the semaphore by o..

Message Queues Message queues are the primary means of interthread communication in ThreadX. One or more messages can reside in a message queue. A message queue that holds a single message is commonly called a mailbox. Messages are copied to a queue by tx_queue_send and are copied from a queue by tx_queue_receive. The only exception to this is when a thread is suspended while waiting for a messa..

이번 글은 RTOS의 중요한 기능중 하나인 Thread에 대해 다룰 것이므로 주의 깊게 보시기를 추천드립니다 Thread Execution Scheduling and executing application threads is the most important activity of ThreadX. What exactly is a thread? A thread is typically defined as semi-independent program segment with a dedicated purpose. The combined processing of all threads makes an application. How are threads created? Threads are created dynamica..

Understanding the initialization process is very important. The initial hardware environment is setup here. In addition, this is where the application is given its initial personality. ThreadX attempts to utilize (whenever possible) the complete development tool’s initialization process. This makes it easier to upgrade to new versions of the development tools in the future. 초기화 프로세스를 이해하는 것은 매우 ..

참조글 : THREADX.PDF 여기도 도움이 된다. https://ppua.tistory.com/entry/%EC%8B%A4%EC%8B%9C%EA%B0%84-%EC%9A%B4%EC%98%81%EC%B2%B4%EC%A0%9C-RTOS%EC%9D%98-%EC%9D%B4%ED%95%B4 Memory Usage ThreadX resides along with the application program. As a result, the static memory (or fixed memory) usage of ThreadX is determined by the development tools; e.g., the compiler, linker, and locator. Dynamic memory (or run-time..