topic Re: Will the config tools and LPUART_Init function support inverting the UART polarity? in MCX Microcontrollers

Will the config tools and LPUART_Init function support inverting the UART polarity?

rj_engineer — Wed, 30 Jul 2025 13:03:28 GMT

Hi,

The CTRL register of the MCXA UART contains the TXINV (28) bit which control the polarity of the UART.

However, the config tools doesn't expose this functionnality and the "LPUART_Init" function automatically unset this bit. The only solution found was to disable the RX and TX output (after the "LPUART_Init") to set the TXINV.

LPUART1_PERIPHERAL->CTRL &= ~LPUART_CTRL_TE_MASK; LPUART1_PERIPHERAL->CTRL &= ~LPUART_CTRL_RE_MASK; LPUART1_PERIPHERAL->CTRL |= LPUART_CTRL_TXINV_MASK; LPUART1_PERIPHERAL->CTRL |= LPUART_CTRL_TE_MASK; LPUART1_PERIPHERAL->CTRL |= LPUART_CTRL_RE_MASK;

This solution cause unnecessary rising edge on the UART lines.

Writing a custom UART init function is overkill and error prone.

The question is :

Is there any other "proper" way to invert the UART polarity and are the config tools scheduled to support this functionnality.

Sincerely,

Re: Will the config tools and LPUART_Init function support inverting the UART polarity?

Alice_Yang — Thu, 14 Aug 2025 08:45:05 GMT

Hi @rj_engineer

I'm sorry for replying to you late.

1. I have checked the config tool, and it indeed doesn't support this feature. I will submit a feature request to the config tool development team. Thank you

2. We can add this configuration through code, such as

LPUART_CTRL_TXINV(1); // Enable Transmit Data Inversion

Please contact me if still have any question.

Alice

Re: Will the config tools and LPUART_Init function support inverting the UART polarity?

rj_engineer — Wed, 03 Sep 2025 13:44:03 GMT

Thank you for the answer