imx rt 1020 - 9bit uart

[bp1979]

Hi,

Is there any proper documentation available how to get 9bit uart working on an imx rt 1020 EVK board? These posts don't give me much direction yet.

Some experiences with iMX.6 9-bit UART mode - NXP Community

Solved: IMX6 UART 9 bit MDB protocol - NXP Community

LPC5526 9bit uart multiprocessor setup - NXP Community

- Do I really need to rewrite the fsl_lpuart driver? If yes, any advise how/where to begin?

- There are tons of SDK examples, but none for 9bit uart, am I looking in the wrong direction?

Many thanks in advance, (in depth) help is greatly appreciated!

UPDATE:

I've read the reference manual, helped a lot. Also had a more detailed glance at the fsl_lpuart driver. Seems that all I have to do is enable 9bit mode by setting CTRL[M] register. Then the uart peripheral will transmit/receive 9 data bits in its shift register and copy the value to the DATA register. 

So how does this exactly work with the interrupts and DMA?

For DMA: Do I set the DMA transfer to 2 x uint8_t?

For receive with interrupt: do I simply read uint16_t from the DATA register when the RDRF interrupt fires?

[jeremyzhou · Accepted solution]

Hi,
Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
1) Do I set the DMA transfer to 2 x uint8_t?
-- You should set DMA to read 16-bits per request.
2) Do I simply read uint16_t from the DATA register when the RDRF interrupt fires?
-- Yes.
Have a great day,
TIC

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