1952872_en-US

[#1]

s32k312 pwm period & icu configuration

Hello, I am currently working with the PWM input and capture functions of the s32k312, and I have a few questions I would like to confirm with you:

Regarding the calculation of PWM output frequency: Is the formula used as follows to determine the frequency?
Frequency = core_clk / (master bus prescaler) / (clock prescaler) / tick
For example: Frequency = 120MHZ / 1 / 12 / 5000 = 200HZ

When capturing PWM period and duty cycle through the ICU, does the ICU start capturing immediately after initialization, and is there a running cycle for this process?

Re: s32k312 pwm period & icu configuration

Emios_Pwm_Ip_SetDutyCycle is different from Pwm_SetDutyCycle.
Your understanding is suitable for Pwm_SetDutyCycle:
0x0000 means 0%
0x8000 means 100%

But the duty cycle of Emios_Pwm_Ip_SetDutyCycle is calculated as follows: NewDutyCycle/Period[ticks]
3276/50000=6.55%
6553/20000=32.765%
It matches your test results.

Re: s32k312 pwm period & icu configuration

Alright, I understand. I'm currently testing, thank you. Additionally, I have one more question regarding the duty cycle. I'm not sure if my calculations are correct, so I would appreciate your guidance. I'm currently using the function Emios_Pwm_Ip_SetDutyCycle(uint8 Instance, uint8 Channel, Emios_Pwm_Ip_DutyType NewDutyCycle) to set the duty cycle:

When I set the frequency to 200Hz and pass NewDutyCycle=3276.8, the duty cycle measured by the oscilloscope is not 10% but 6.5%.
When I set the frequency to 500Hz and pass NewDutyCycle=6553.6, the duty cycle is not 20% but 32%.
Can you please tell me where my configuration might be incorrect?"

Re: s32k312 pwm period & icu configuration

Hi

Seems that emios is configured as OPWFMB mode.  Clock Divider Value in Emios_Mcl_Ip is used to calculate PWM frequency.

Frequency = core_clk / (Clock Divider Value) / (clock prescaler) / tick

Please verify it by testing.

Please refer to the S32K344_Example_Emios_Icu_IPWM_measurement_DS34_RTD_100_v2 :

/*Start measuring */

Emios_Icu_Ip_StartSignalMeasurement(EMIOS1, EMIOS_ch1);

Emios_Icu_Ip_GetInputState(EMIOS1, EMIOS_ch1);

/* Get captured duty-cycle and period*/

Emios_Icu_Ip_GetDutyCycleValues(EMIOS1, EMIOS_ch1, &ic_result_temp);

/* If captured */

if(ic_result_temp.PeriodTime)

{

/* Stop measuring */

Emios_Icu_Ip_StopSignalMeasurement(EMIOS1, EMIOS_ch1);

captured = 1;

}

Best Regards,
Robin
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