IMXRT1024 LPUART FIFO Issue

[Lukas_Frank]

Hi all,

I'm setting the LPUART FIFO RX and TX sizes and it only seems to be 4 words and cannot be set to any other value.  In the RM it says maximum number of receive or transmit fifo size data word can be up to 256 words. 

I have examine the following register:

Parameter Register (PARAM)

LPUART FIFO Register (FIFO)

LPUART Watermark Register (WATER)

But nothing is work to set my FIFO size..

How can I set it manually?

Why do you write, from 1word to 256word, on RM like a size-scale for FIFO if I am not able to use that size?

Thanks and Regards.

[danielchen]

Hi @Lukas_Frank :

From the source code, you can configure the FIFO size the before LPUART_INIT function

/*
* config.baudRate_Bps = 115200U;
* config.parityMode = kLPUART_ParityDisabled;
* config.stopBitCount = kLPUART_OneStopBit;
* config.txFifoWatermark = 0;
* config.rxFifoWatermark = 0;
* config.enableTx = false;
* config.enableRx = false;
*/
LPUART_GetDefaultConfig(&config);
config.baudRate_Bps = BOARD_DEBUG_UART_BAUDRATE;
config.enableTx = true;
config.enableRx = true;

config.txFifoWatermark = your size;

config.rxFifoWatermark = youe size;

LPUART_Init(DEMO_LPUART, &config, DEMO_LPUART_CLK_FREQ);

Regards

Daniel

[danielchen]

Sorry, I made a mistake here, watermark is not FIFO size.

Please refer to LPUART FIFO register for FIFO size.

danielchen_0-1629794582818.png

danielchen_1-1629794605355.png

You can configure this register for FIFO size.

Regards

Daniel

[Lukas_Frank]

Dear @danielchen Hi again,

I set it, but there was no action more than 4 word. Also RM is spesified that this field is read only. When I set RXFIFOSIZE to 256, it still returns RXCOUNT as 4 word maximum. I am just trying to measure what is the size of incoming bytes. What is the truth about FIFO?

Lukas_Frank_0-1629873691603.png

Lukas_Frank_2-1629873764051.png

Could you please also view my other question?

Question Get Send/Receive Data Count 

Thanks and Regards.

[danielchen]

Sorry, I confirmed with hardware team,  The RXFIFO size is 4 data words.  It is a fixed value, a hardware attribute, not configurable.

Regards

Daniel

[Lukas_Frank]

Hi @danielchen,

I set it, but there was no action more than 4 word. There is an assert rule in LPUART_Init. So I am not able to set my FIFO size more than 4. But in reference manual it is read-only form from 1word to 256word. What is the actual size of this FIFO? I indicate that in my question why do not you choose not to answer it ? 

Could you please view my other question? Question Get Send/Receive Data Count 

Thanks and Regards.