issues with configuring spread spectrum on the RT1170.

[sajithdevidas]

Hi,

We are working with custom boards based on the RT1170, and using the MCU Xpresso IDE. To pass the EMI/EMC test, we need to drive the SEMC clock root through any of the main clocks that support spread spectrum. However, according to the datasheet, SEMC only supports the following main clocks which is having spread spectrum

- SEMC_ClockRoot_MuxSysPll1Div5

- SEMC_ClockRoot_MuxSysPll2Out

- SEMC_ClockRoot_MuxSysPll2Pfd1

Except for these clocks, all the others do not support spread spectrum. We attempted to work with PLL2, but encountered the following error

 I am providing a forum link that discusses a similar issue.

https://community.nxp.com/t5/i-MX-RT/i-MX-RT1170-Failed-to-boot-after-Spread-Spectrum-Clocking-is/m-...

i.MX RT1170 Failed to boot after Spread Spectrum Clocking is enabled Trying to enable SSC on RT1170 EVK with MCUXpresso. Ref: AN12879 Steps: 1. Base project: SDK Example evkmimxrt1170_semc_cm7 2. Using IDE to config SSC  3. Boot failed 4. Sometimes can boot normally (~ 1/50) Any step I missed? Regards Seen community.nxp.com

The alternative option is to drive it through PLL1. According to AN12879, for instance, we are attempting to set 12MHz as the range and 60Hz as the step. However, configuring this through the configtools has not been successful. There are various constraints to consider, such as the input being 24MHz, the output being 1GHz, etc. Also, setting the range and step has been unsuccessful.

Kindly address this issue and provide a reply as soon as possible. Thank you.

Sajith P

[Kan_Li]

Hi @sajithdevidas ,

Did you try the demo from https://community.nxp.com/t5/i-MX-RT/i-MX-RT1170-Failed-to-boot-after-Spread-Spectrum-Clocking-is/m-... on RT1170 EVK? Does it work or still fail? Please kindly clarify.

Have a great day,
Kan

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[sajithdevidas]

Yes, i tried,
But my code is working on SDRAM, and when i am trying to put the fsl_clock.c into the SRAM_OC1, but the fsl_clock.o is of 3.3MB, i don't know why it is this much big, and it is not fit in that region,

[Kan_Li]

Hi @sajithdevidas ,

The demo would not take so many memory resource, did you change it according to your custom board? It just takes about 10k here for SRAM_OC1.

Is it possible to share your code for a review?

Have a great day,
Kan

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[sajithdevidas · Accepted solution]

Hi @Kan_Li 

We have identified the issue. The code includes lvgl, and in the linker script, we are including "bss.ldt", which is taking up extra space.

<#if memory.name=="SRAM_OC1"> *(.bss*) </#if>

After removing the "bss.ldt" file, the spread spectrum feature is enabled successfully.

However, a new issue has arisen. The boot-up time of my code has increased to 2-3 seconds, whereas previously it was instantaneous. This delay occurs only when spread spectrum is enabled. If I disable spread spectrum, the boot-up time returns to normal.

Please respond as soon as possible. Thank you for your patience

[Kan_Li]

Hi @sajithdevidas ,

It is hard to advise without your code, so is it possible to tell us how you disable spread spectrum and how you enable it? Thanks for your patience!

Have a great day,
Kan

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[sajithdevidas]

thank you @Kan_Li ,
the issue has been solved,

[sajithdevidas]

hi @Kan_Li ,

we are not using RT1170 EVK board, we are using our own custom board which runs on RT1176xx