Dear NXP Support Team,
I am currently developing on the RT1170 using SDK with LPUART1 for UART communication. I am encountering an issue with Send BREAK detection and would like your guidance.
Description of the issue:
When I enable LIN Break Detection (LBKDE) and LBKDIE:
The Send BREAK signal from the PC is successfully detected on the MCU (LBKDIF flag is set).
However, normal UART data communication not working.
RX and TX are working correctly in normal UART mode.
Scope measurements show that the PC’s TX line stays low during the Send BREAK for the expected duration (~2100 ms).
Question:
Is this behavior expected on RT1170 LPUART?
Is there a recommended way to detect a PC Send BREAK while still allowing normal UART communcation?
I would appreciate your guidance on how to reliably detect a Send BREAK from a PC while maintaining normal UART data reception on RT1170.
Thank you for your assistance.
Best regards,
Dear NXP Support Team,
Thank you for your previous explanation and the reference to the RT1170 Reference Manual.
Based on the RM description, we understand that when LBKDE = 1, the LIN break detection circuit is enabled and received data is not written to the RX FIFO, so normal UART reception is intentionally disabled. We acknowledge that this behavior is expected.
However, we would like to ask a follow-up question regarding possible alternatives or recommended solutions.
Our requirement
Detect a Send BREAK condition from a PC (via USB-UART).
At the same time, continue normal UART data transmission and reception.
LIN protocol stack is not required; this is general UART communication with a BREAK used as a synchronization or control signal.
What we have observed
With LBKDE = 1
LIN BREAK is detected correctly (LBKDIF is set).
Normal UART RX data is blocked, as described in the RM.
With LBKDE = 0
Normal UART RX works correctly.
Our questions
Is there any supported or recommended method on RT1170 to detect a Send BREAK while keeping normal UART RX active, without enabling LBKDE?
Is using Framing Error (FE) + RX FIFO flush considered the intended workaround for non-LIN UART BREAK detection?
Are there any errata, undocumented settings, or hardware limitations related to using LBKDE with general UART communication?
If this use case is not supported, could you please confirm that RT1170 LPUART does not support simultaneous LIN BREAK detection and normal UART reception by design?
We would appreciate your confirmation or any recommended best practices for this scenario.
Thank you very much for your continued support.
Best regards,
Hi @dskim2 ,
Thanks for your interest in NXP MIMXRT series!
The phenomenon you described is expected. Please refer to the following explanation from RM:
Additionally, one of our colleagues has implemented a similar feature that may be helpful to you:
Best regards,
Gavin