---
source_url: https://www.pubnub.com/docs/sdks/freertos/troubleshoot
title: Troubleshooting FreeRTOS SDK
updated_at: 2026-06-03T11:42:24.013Z
sdk_name: PubNub FreeRTOS SDK
---

> Documentation Index
> For a curated overview of PubNub documentation, see: https://www.pubnub.com/docs/llms.txt
> For the full list of all documentation pages, see: https://www.pubnub.com/docs/llms-full.txt


# Troubleshooting FreeRTOS SDK

PubNub FreeRTOS SDK

This page explains how to use the assertion subsystem for troubleshooting in the PubNub FreeRTOS Software Development Kit (SDK).

## Using the PUBNUB_ASSERT subsystem

The `PUBNUB_ASSERT` subsystem helps you catch and fix bugs when working with the FreeRTOS SDK.

When your code hits an unexpected condition, assertions immediately flag the problem and show exactly which file and line caused the error. You can control how strict these checks are - use more checks during development to catch more issues, or fewer checks in production for better performance.

C-core has its own `ASSERT` module/subsystem. Its interface is in the header `pubnub_assert.h`. It is used in C-core modules themselves, but you can also use it in your code if you wish. It provides several levels of `ASSERTs`:

| Level | Preprocessor Symbol | Description |
| --- | --- | --- |
| highest | `PUBNUB_ASSERT_LEVEL_EX` | All checks enabled (compiled). |
| regular | `PUBNUB_ASSERT_LEVEL` | Only the long lasting checks are disabled, other are compiled. |
| lowest | `PUBNUB_ASSERT_LEVEL_OPT` | Only the checks with negligible execution length are enabled. |
| none | `PUBNUB_ASSERT_LEVEL_NONE` | All checks disabled. |

The default level is `regular`, and that is the level used in our samples.

If you want the highest level for troubleshooting, define the `PUBNUB_ASSERT_LEVEL_EX` preprocessor symbol when compiling. If you want to troubleshoot performance by disabling checks, define `PUBNUB_ASSERT_LEVEL_NONE`.

Also, you can control what happens when an assertion fails. To do that, you set a `callback` function to be called, by using `pubnub_assert_set_handler()`, which should be called as early as possible in the execution of your program.

There are a few `ready-made` handlers which you can use and the default is `pubnub_assert_handler_abort`, which provides a similar operation as the C standard `assert()` macro - prints a report of the place and expression of the assertion and then aborts. These handlers use the `FreeRTOS_printf` macro, which is not part of FreeRTOS "proper", so it might not be available in your configuration.

If you wish to provide your own handler, you need to define a function that conforms to the following `typedef`:

```c
typedef void (*pubnub_assert_handler_t)(char const *s, char const *file, long line);
```

For example:

```c
void dbg_break_assert_handler(char const *s, char const *file, long line)
{
    FreeRTOS_printf(("Will hit breakpoint for '%s' in %s line %d\n", s, file, line));
    BREAK_IN_DEBUGGER; /* assuming you have such a macro */
}
```