# 适用于开发完整应用的模版
An application can be written to run as either a task (a module with its own stack and process priority) or as a work queue task (a module that runs on a work queue thread, sharing the stack and thread priorit with other tasks on the work queue). In most cases a work queue task can be used, as this minimizes resource usage.
注解
Architectural Overview > Runtime Environment provides more information about tasks and work queue tasks.
注解
All the things learned in the First Application Tutorial are relevant for writing a full application.
# Work Queue Task
PX4-Autopilot contains a template for writing a new application (module) that runs as a work queue task: src/examples/work_item (opens new window).
PX4 固件中包含了一个模版文件: src/templates/module (opens new window) ,基于该模版编写的应用(模块)可以在应用自己的栈上执行 任务 。
The example shows how. In summary:
- Specify the dependency on the work queue library in the cmake definition file (CMakeLists.txt (opens new window)):
... DEPENDS px4_work_queue
- In addition to
ModuleBase
, the task should also derive fromScheduledWorkItem
(included from ScheduledWorkItem.hpp (opens new window)) - Specify the queue to add the task to in the constructor initialisation. The work_item (opens new window) example adds itself to the
wq_configurations::test1
work queue as shown below:WorkItemExample::WorkItemExample() : ModuleParams(nullptr), ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::test1) { }
注解
The available work queues (wq_configurations
) are listed in WorkQueueManager.hpp (opens new window).
- Implement the
ScheduledWorkItem::Run()
method to perform "work". - Implement the
task_spawn
method, specifying that the task is a work queue (using thetask_id_is_work_queue
id. - Schedule the work queue task using one of the scheduling methods (in the example we use
ScheduleOnInterval
from within theinit
method).
# Tasks
PX4/PX4-Autopilot contains a template for writing a new application (module) that runs as a task on its own stack: src/templates/template_module (opens new window).
The template demonstrates the following additional features/aspects that are required or are useful for a full application:
- 访问参数并对参数更新做出反应。
- 订阅、等待 topic 更新。
- 通过
start
/stop
/status
控制后台运行的任务。module start [<arguments>]
命令可以直接加入 启动脚本 中。 - 命令行参数解析。
- 文档记录:
PRINT_MODULE_*
方法有两个用处(该 API 在 源代码 (opens new window) 中有详细记录):- 它们可用于在控制台键入
module help
指令后输出命令行指令的用法。 - 可通过脚本提取该部分内容以自动生成 Modules & Commands Reference 页面。
- 它们可用于在控制台键入