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FreeRTOS+ Ecosystem Showcase  New File System:  DOS compatible FAT FS  UDP/IP:  Thread aware UDP stack  Trace:  Run-time analysis tool  IO:  read(), write(), ioctl() interface  CLI:  Command line interface  Nabto:  Webserver in 1K, see how  TCP/IP:  Low cost pre-ported libraries  CyaSSL SSL / TLS:  Networking security protocols  Safety:  TUV certified RTOS for MCUs  RTOS Training:  Delivered online or on-site FreeRTOS Sponsors Last site update May 1 2013		FreeRTOS Sponsors Get seen by 1000s of embedded engineers a month Software Timers [Getting Started] From this page: Software timers in a nutshell Efficiency considerations in software timer implementations Important information on writing timer callback functions The timer service/daemon task, and the timer command queue Configuring an application to use software timers One-shot timers versus auto-reload timers Resetting a software timer API Software timers in a nutshell A software timer (or just a 'timer') allows a function to be executed at a set time in the future. The function executed by the timer is called the timer’s callback function. The time between a timer being started, and its callback function being executed, is called the timer’s period. Put simply, the timer's callback function is executed when the timer's period expires. Note, a software timer must be explicitly created before it can be used. Efficiency considerations in software timer implementations Software timer functionality is easy to implement, but difficult to implement efficiently. The FreeRTOS implementation does not execute timer callback functions from an interrupt context, does not consume any processing time unless a timer has actually expired, does not add any processing overhead to the tick interrupt, and does not walk any link list structures while interrupts are disabled. The timer service task (primarily) makes use of existing FreeRTOS features, allowing timer functionality to be added to an application with minimal impact on the size of the application's executable binary. Important information on writing timer callback functions Timer callback functions execute in the context of the timer service task. It is therefore essential that timer callback functions never attempt to block. For example, a timer callback function must not call vTaskDelay(), vTaskDelayUntil(), or specify a non zero block time when accessing a queue or a semaphore. [ Back to the top ]    [ About FreeRTOS ]    [ Sitemap ]    [ ] Copyright (C) 2004-2010 Richard Barry. Copyright (C) 2010-2013 Real Time Engineers Ltd. Any and all data, files, source code, html content and documentation included in the FreeRTOSTM distribution or available on this site are the exclusive property of Real Time Engineers Ltd.. See the files license.txt (included in the distribution) and this copyright notice for more information. FreeRTOSTM and FreeRTOS.orgTM are trade marks of Real Time Engineers Ltd.