Task Priorities¶

This document describes the thread priorities configured in the RTK Base firmware.

Priority Overview¶

Tasks are assigned priorities using FreeRTOS priority levels (0-24, where higher numbers = higher priority).

Task List¶

Task Name	Status	Prio	HWM	Task#	CPU	Description
esp_timer	B	22/22	3788	1	0	ESP-IDF timer service
ipc0	B	24/24	428	2	0	Inter-processor communication (CPU0)
ipc1	B	24/24	396	3	1	Inter-processor communication (CPU1)
main	R	1/1	332	5	0	Main application loop
IDLE0	R	0/0	924	6	0	Idle task (CPU0)
IDLE1	R	0/0	924	7	1	Idle task (CPU1)
Tmr Svc	B	1/1	1132	8	0	FreeRTOS timer service
tiT	B	18/18	3112	12	0	TCP/IP task
sys_evt	B	20/20	1420	13	0	System event handler
long_work	B	1/1	12844	14	x	Long-running background work
debug_task_core	B	10/10	1988	15	1	Debug output task
uart_msg_manage	B	16/16	1036	16	1	UART message management
wifi	B	23/23	2988	17	0	WiFi driver task
emac_rx	S	15/15	3128	18	x	Ethernet MAC receive
httpd	B	23/23	4900	19	x	HTTP server
uart-tcp	B	5/5	1308	20	x	UART-TCP bridge
periodic_task	B	10/10	3252	21	x	Periodic maintenance
ZedMainTask	B	23/23	1480	22	x	ZED GNSS main task
mqtt_task	B	5/5	2236	23	x	MQTT client task

Legend: - Status: R = Running, B = Blocked, S = Suspended - Prio: Current / Base priority - HWM: High Water Mark (stack usage) - CPU: x = Any CPU, 0/1 = Affinity

Priority Groups¶

Critical System (22-24)¶

Purpose: Core ESP-IDF infrastructure

Task	Priority	Notes
ipc0	24	Must preempt all for system calls
ipc1	24	Same for CPU1
wifi	23	WiFi timing critical
httpd	23	HTTP server responsiveness
ZedMainTask	23	GNSS data processing
esp_timer	22	Hardware timer accuracy

Network Stack (15-20)¶

Purpose: Network communication

Task	Priority	Notes
sys_evt	20	System events
emac_rx	15	Ethernet receive (can be interrupted)
uart_msg_manage	16	UART message handling
tiT	18	TCP/IP stack

Application Core (10-14)¶

Purpose: Main application logic

Task	Priority	Notes
debug_task_core	10	Debug output
periodic_task	10	Regular maintenance

Background Tasks (1-5)¶

Purpose: Non-critical background operations

Task	Priority	Notes
mqtt_task	5	MQTT client (network tolerant)
uart-tcp	5	UART-TCP bridge
main	1	Main loop
Tmr Svc	1	Software timers
long_work	1	Background processing

Idle (0)¶

Purpose: CPU power management

Task	Priority	Notes
IDLE0	0	CPU0 idle
IDLE1	0	CPU1 idle

Task Affinity¶

CPU0 Tasks¶

esp_timer
ipc0
main
IDLE0
tiT
sys_evt
wifi

CPU1 Tasks¶

ipc1
IDLE1
debug_task_core
uart_msg_manage

Any CPU (x)¶

long_work
emac_rx
httpd
uart-tcp
periodic_task
ZedMainTask
mqtt_task

Stack Usage¶

High Stack Users (>3000 bytes)¶

Task	HWM	Reason
httpd	4900	HTTP request/response buffers
long_work	12844	File operations, updates
tiT	3112	TCP/IP stack
emac_rx	3128	Ethernet frame buffers
periodic_task	3252	JSON processing

Medium Stack Users (1000-3000 bytes)¶

Task	HWM	Reason
wifi	2988	WiFi driver
sys_evt	1420	Event handling
mqtt_task	2236	MQTT protocol
ZedMainTask	1480	UBX protocol

Low Stack Users (<1000 bytes)¶

Task	HWM	Reason
ipc0	428	Simple messages
ipc1	396	Simple messages
main	332	Event loop

Configuration¶

Changing Priorities¶

Via Console:

dbg task prio <ID> <PRIO>

In Code:

vTaskPrioritySet(task_handle, new_priority);

Recommendations¶

Never lower critical system tasks (ipc, wifi)
Test thoroughly when modifying priorities
Monitor HWM for stack overflow detection
Balance between responsiveness and fairness

Monitoring¶

Runtime Statistics¶

View current task status:

dbg task

Stack Monitoring¶

Check high water marks:

dbg heap

Performance Impact¶

Priority changes affect: - Response latency - CPU utilization - Power consumption - Real-time guarantees