Trace hooks and FreeRTOS+Trace - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a trace hook function that runs when a task is switched in.

FreeRTOS

void traceTASK_SWITCHED_IN(void) {
    [1];
}

Drag options to blanks, or click blank then click option'

Aprintf("Task switched in\n")

BvTaskDelay(10)

CxTaskCreate()

DvTaskDelete(NULL)

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to create or delete tasks inside the trace hook.

Using delay functions inside trace hooks.

The trace hook traceTASK_SWITCHED_IN is used to run code when a task is switched in. Using printf here logs the event.

2fill in blank

medium

Complete the code to enable FreeRTOS+Trace recording in the configuration.

FreeRTOS

#define configUSE_TRACE_FACILITY [1]

Drag options to blanks, or click blank then click option'

A0

B2

C3

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the value to 0 disables tracing.

Using values greater than 1 which are not valid.

Setting configUSE_TRACE_FACILITY to 1 enables trace facility support in FreeRTOS.

3fill in blank

hard

Fix the error in the trace hook function to correctly record a task switch event.

FreeRTOS

void traceTASK_SWITCHED_OUT(void) {
    [1](pxCurrentTCB->pxTaskTag);
}

Drag options to blanks, or click blank then click option'

AvTraceStart

BvTraceStoreTaskSwitchedOut

CxTaskCreate

DvTaskDelay

Attempts:

3 left

💡 Hint

Common Mistakes

Using delay or task creation functions inside trace hooks.

Calling functions unrelated to tracing.

The function vTraceStoreTaskSwitchedOut records the task switch out event for FreeRTOS+Trace.

4fill in blank

hard

Fill both blanks to create a dictionary of task names and their run times using FreeRTOS+Trace API.

FreeRTOS

for (int i = 0; i < uxTaskGetNumberOfTasks(); i++) {
    char* name = pcTaskGetName([1]);
    uint32_t time = ulTaskGetRunTimeCounter([2]);
    taskTimes[name] = time;
}

Drag options to blanks, or click blank then click option'

Ai

BpxCurrentTCB

CNULL

DxTaskGetHandle(NULL)

Attempts:

3 left

💡 Hint

Common Mistakes

Using NULL or current task handle instead of the loop index.

Mixing task handles and indexes incorrectly.

Using xTaskGetHandle(NULL) is incorrect here; to get task handles by index, FreeRTOS does not provide a direct API. Instead, the correct approach is to use uxTaskGetSystemState() to get an array of task status structures. Since the question uses index i, the correct function to get the task handle is xTaskGetHandle() with the task name or from the system state array. Given the options, the best fit is D for both blanks, assuming xTaskGetHandle() is used with the task name.

5fill in blank

hard

Fill all three blanks to start trace recording, record a task switch, and stop recording.

FreeRTOS

vTrace[1]();
vTrace[2](pxCurrentTCB->pxTaskTag);
vTrace[3]();

Drag options to blanks, or click blank then click option'

AStart

BStoreTaskSwitchedIn

CStop

DReset

Attempts:

3 left

💡 Hint

Common Mistakes

Using reset instead of stop to end trace.

Not calling the store function for task switch.

Start trace recording with vTraceStart(), record task switch with vTraceStoreTaskSwitchedIn(), and stop with vTraceStop().