Input PWM Duty cycle measurement Issue using S32K312 eMIOS SAIC mode

CCY_Yu — Tue, 06 May 2025 03:33:15 GMT

Dear NXP Support Team,

I am currently working with the S32K312 and using the eMIOS ICU in SAIC mode to measure a PWM signal. However, I am observing inconsistent and inaccurate results in the measured duty cycle and period time.

System Setup:

PWM Output Pin: PTA12
- Configured using eMIOS_0 channel 8 in OPWMB mode
ICU Input Pin: PTC11
- Configured using eMIOS_1 channel 1 in SAIC (IPWM) mode
Connection: PTA12 (PWM output) is physically connected to PTC11 (ICU input)

Signal Characteristics:

PWM frequency: 1 Hz
Duty cycle: 5 ms high time
Verified by oscilloscope: waveform is stable and correct

🧭 Clock Configuration:

Core clock: 80 MHz
eMIOS global clock: divided by 160 → 0.5 MHz
OPWMB prescaler: ÷10 → Tick = 20 µs (50 kHz)
SAIC measurement also uses BUS_DIVERSE, with same tick = 20 µs

Observed Issue:

The expected measured values (based on 20 µs ticks) should be:
- PeriodTime ≈ 50,000 ticks
- ActiveTime ≈ 250 ticks (5 ms ÷ 20 µs)
However, most of the time we observe:
- ActiveTime = 285
- PeriodTime = 285 (unexpected, matches active time)
Occasionally:
- ActiveTime = 285
- PeriodTime = 50000 (correct)

This suggests that in most cases, the period time is not measured properly and may be overwritten or missed.

Request:

Could you please help us understand:

How to correctly configure eMIOS ICU in SAIC mode to reliably measure both ActiveTime and PeriodTime for low-frequency PWM input?
Are there specific timing or synchronization requirements between the OPWMB and SAIC channels?
Is there any known issue or workaround for measuring low-frequency PWM (e.g., 1 Hz) using this setup?

Attached below is the scope snapshot and software configuration if needed.

Thank you for your support.

Here is the detailed configuration:
*
* Connect PTC12 (PWM) to PTC11 (SAIC)
* PWM signal generated by EMIOS_0_ch8 (in OPWMB mode) is measured by EMIOS_1_ch_0 (SAIC mode).
*
* EMIOS_0 global global clock (core clock = 80MHz) prescaled in EMIOS_Mcl driver (/160) = 0.5MHz.
*
* Internal BUS generated by EMIOS_0_ch_8
* Tick = 20us (0.5MHz global clock prescaled by 10 = 50kHz)
*
* PWM (OPWMB), EMIOS_0_ch_8, PTA12
* Tick = 20us (0.5MHz global clock prescaled by 10 = 50kHz)
*
* IC (IPWM), EMIOS_1_ch_0, PTC11
* Clocked by Internal BUS (Diverse)
* Tick = 20us

Re: Input PWM Duty cycle measurement Issue using S32K312 eMIOS SAIC mode

Senlent — Tue, 06 May 2025 05:52:03 GMT

Hi@CCY_Yu

The description of the problem is very detailed.

Can you provide your test project so that I can help you find the cause of the problem?

Re: Input PWM Duty cycle measurement Issue using S32K312 eMIOS SAIC mode

CCY_Yu — Tue, 06 May 2025 07:39:46 GMT

This feature was developed based on an ongoing customer project.
Due to company policy, I am unable to provide the full source code.

However, would it be helpful if I share the S32K MEX configuration file for your review?

Re: Input PWM Duty cycle measurement Issue using S32K312 eMIOS SAIC mode

Senlent — Tue, 06 May 2025 07:46:21 GMT

Hi@CCY_Yu

It's okay, I can make a similar demo, but it will take me some time.

Aslo, please tell me the RTD version you're using.

topic Input PWM Duty cycle measurement Issue using S32K312 eMIOS SAIC mode in S32K

Input PWM Duty cycle measurement Issue using S32K312 eMIOS SAIC mode

System Setup:

Signal Characteristics:

🧭 Clock Configuration:

Observed Issue:

Request:

Re: Input PWM Duty cycle measurement Issue using S32K312 eMIOS SAIC mode

Re: Input PWM Duty cycle measurement Issue using S32K312 eMIOS SAIC mode

Re: Input PWM Duty cycle measurement Issue using S32K312 eMIOS SAIC mode