System Tasks

This document explains the ESP8266 RTOS SDK internal system tasks.

Overview

The main tasks and their attributes are as following:

Names	stack size	Priority
uiT	3584(C)	14
IDLE	768	0
Tmr	2048(C)	2
ppT	2048(C)	13
pmT	1024	11
rtT	2048	12
tiT	2048(C)	8
esp_event_loop_task	2048(C)	10

Note: (C) means it is configurable by “menuconfig”.

Tasks Introduction

uiT

This task initializes the system, including peripherals, file system, user entry function and so on. This task will delete itself and free the resources after calling app_main.

IDLE

This task is freeRTOS internal idle callback task, it is created when starting the freeRTOS. Its hook function is vApplicationIdleHook. The system’s function of sleep and function of feeding task watch dog are called in the vApplicationIdleHook.

Tmr

This task is the processor of freeRTOS internal software timer.

ppT

This task is to process Wi-Fi hardware driver and stack. It posts messages from the logic link layer to the upper layer TCP/IP stack after transforming them into ethernet packets.

pmT

The task is for system power management. It will check if the system can sleep right now, and if it is, it will start preparing for system sleep.

rtT

The task is the processor of high priority hardware timer. It mainly process Wi-Fi real time events. It is suggested that functions based on this component should not be called in application, because it may block other low layer Wi-Fi functions.

tiT

The task is the main task of TCP-IP stack(LwIP) , it is to deal with TCP-IP packets.

esp_event_loop_task

The task processes system events, for example, Wi-Fi and TCP-IP stack events.

Suggestions

In general, the priority of user task should NOT be higher than the system real timer task’s priority (12). So it is suggested that keep your user tasks’ priorities less than 12. If you want to speed up the TCP/UDP throughput, you can try to set the priority of send/receive task to be higher than the “tiT” task’s priority (8).