S32K344 - LPUART Tx Send Hard Fault

[DiaDev]

Hi,

I'm working on an S32K platform using FreeRTOS. I have two tasks (UartTask1 and UartTask2) that frequently call debug_log() to send messages over UART.

Logging structure:

• debug_log() formats the message and enqueues it into a FreeRTOS queue.

• A dedicated uart_log_task() dequeues and sends each message using Lpuart_Uart_Ip_AsyncSend().

• UART TX completion is confirmed using a callback that sets a uart_tx_done flag.

• A small vTaskDelay() is added after UART transmission in the log task — no queue overflow is observed.

Issue:
Every time UART starts sending, only a few characters are printed or sometimes garbage, and then the system hits a hard fault.

This happens consistently during UART transmission, not before.

Key finding:
When I isolate UART and test it outside of the logging system (no queue, no multiple tasks), it works fine. So the UART driver itself seems okay.

Question:

• What could be causing this crash in the multitask logging setup?

• Is it possible that a shared/static buffer (like tx_data) is getting overwritten or accessed before TX completes?

• Are there specific precautions for using Lpuart_Uart_Ip_AsyncSend() with FreeRTOS and multiple tasks?

Any help or suggestions would be greatly appreciated.

Thanks in advance!

I have attached snippet code and lpuart config.

[PetrS · Accepted solution]

Hi,

try to identify a cause of hard fault. You can refer to: How To Debug A Fault Exception On ARM Cortex-M(V7M) MCU(S32K3XX)
Maybe just increasing stack, heap size can help.

BR, Petr