topic Re: MCXN236 FLEXCOMM SPI issue in MCX Microcontrollers

MCXN236 FLEXCOMM SPI issue

seanwu — Mon, 17 Mar 2025 06:42:02 GMT

Dear sir,

I am using lpspi_interrupt_b2b_master, and lpspi_interrupt_b2b_slave examples in MCXN236 SDK 2.16.00 to test SPI function.

I want to check whether it can run 20MHz. But when I set #define TRANSFER_BAUDRATE to 20000000. The data transfer will be error.

Could you please help to check whether FLEXCOMM SPI can run 20MHz, and how to set?

THanks.

BR,

Sean Wu.

Re: MCXN236 FLEXCOMM SPI issue

Harry_Zhang — Mon, 17 Mar 2025 10:41:33 GMT

Hi @seanwu

Regarding speed, you can refer to the MCXN236 data sheet chapter 4.6.2.

After you set #define TRANSFER_BAUDRATE to 20000000.

You also need to two factors:

1. Peripheral Clock Configuration: The SPI baud rate is derived from the peripheral clock. Ensure that the peripheral clock is set appropriately to achieve the desired SPI speed.

2. Baud Rate Divisor: The SPI baud rate is determined by dividing the peripheral clock by a specific divisor. Selecting the correct divisor is crucial for achieving the desired baud rate.

Harry

Re: MCXN236 FLEXCOMM SPI issue

seanwu — Tue, 18 Mar 2025 03:35:32 GMT

Dear @Harry_Zhang ,

This is my setting. Is it OK?

CLOCK_SetClkDiv(kCLOCK_DivFlexcom3Clk, 1u);

CLOCK_AttachClk(kFRO_HF_DIV_to_FLEXCOMM3);

Thanks.

BR,

Sean Wu

Re: MCXN236 FLEXCOMM SPI issue

Harry_Zhang — Tue, 18 Mar 2025 10:11:57 GMT

Hi @seanwu

You can refer to my picture to configure the clock.

After my testing, configuring the clock in this way can meet your requirements.

Harry

Re: MCXN236 FLEXCOMM SPI issue

seanwu — Wed, 19 Mar 2025 01:13:13 GMT

Dear @Harry_Zhang ,

Thanks for your help. I try it as your seeting, and it can run 20MHz. But the main clock will reduce to 120Hz. Does it effect performance?

And I have another question of delay time of pcsToSckDelay, lastSckToPcsDelay, and betweenTransferDelay.

How do I set the value like below code?

masterConfig.pcsToSckDelayInNanoSec = 1000000000U / (masterConfig.baudRate * 2U);

masterConfig.lastSckToPcsDelayInNanoSec = 1000000000U / (masterConfig.baudRate * 2U);

masterConfig.betweenTransferDelayInNanoSec = 1000000000U / (masterConfig.baudRate * 2U);

And in RM, there is a example, but I don't know why.

Thanks.

BR,

Sean Wu

Re: MCXN236 FLEXCOMM SPI issue

Harry_Zhang — Thu, 20 Mar 2025 06:27:00 GMT

Hi @seanwu

"But the main clock will reduce to 120Hz. Does it effect performance?"

I'm just giving you a demonstration, you can adjust the clock according to your needs.

"How do I set the value like below code?"

I think it depends on the slave device’s timing specs.

Harry