topic Re: pwm WS2811 in S32K

pwm WS2811

mswd — Tue, 28 May 2024 03:38:03 GMT

i have a problem that i haven't solved yet.

ㅇ

failed to generate the above waveform.

through searching i found out a few things.

one of them is that control is possible through overinterrupt.

but i don't know how to use it.

ex) how do you set the overinterrupt to 0.5ns?

i need an example for k146.

please help me. thanks.

this is the source code i referenced.

https://community.nxp.com/t5/S32K/S32K144-FTM-Output-Compare-for-Single-Pulse/m-p/844006

Re: pwm WS2811

Robin_Shen — Thu, 30 May 2024 07:45:49 GMT

I did not go through the s32k144_OneShot.zip and their reply completely. Please correct me if I understand it wrong.
I saw that the FTM is configured in Output Compare mode, and it is recommended to modify CnV and MOD to meet your needs (0.5us or 1.2us high pulse , 2.5us period )

Also I don't understand why you want to set overinterrupt to 0.5ns? Shouldn't you set overinterrupt to 0.5us and 1.2us?

Sorry, this example is based on S32K144. It is recommended that you create a new S32K146 project and then add the relevant codes.

Best Regards,
Robin
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Re: pwm WS2811

mswd — Fri, 31 May 2024 09:35:24 GMT

how do i set MOD and CnV to set it to 1.2us?

sorry, but i don't understand pwm settings.

Re: pwm WS2811

Robin_Shen — Mon, 03 Jun 2024 08:44:55 GMT

That example, configure FTM_SC_CLKS(2)=10b - Fixed frequency clock = SIM_LPOCLKS[RTCCLKSEL]=00b - SOSCDIV1_CLK = 8MHz

And FTM_SC_PS(7) means the FTM counter clock = 8MHz/128. This frequency is too low to generate 0.5us and 1.2us. It is recommended to modify the frequency division(FTM_SC_PS(1) ) or select a higher FTM Clock such as 48MHz FIRC.

If you configure FTM_SC_PS(1), then each FTM counter takes 1/8MHz=0.125us
If you want to get 1.2us, then oneshot0 = 1.2/0.125=9.6≈10;

Sorry I am not familiar with s32k144_OneShot.zip. If you don't understand how to use it, I suggest you refer to other MCU examples to use DMA or FlexIO.

NeoShield: WS2812 RGB LED Shield with DMA and nRF24L01+

NXP FlexIO Generator for the WS2812B LED Stripe Protocol