PWM Spike on starting/stopping on all channels

RE: PWM Spike on starting/stopping on all channels

Sigurd — Wed, 10 Sep 2025 10:51:36 GMT

[quote user="max00"]thank you very much for the feedback - I just tested it myself and it looks great now![/quote]

Great!

[quote user="max00"]Do you have any idea what change fixed this? Just out of curiosity![/quote]

I believe it was fixed with this commit here: https://github.com/nrfconnect/sdk-zephyr/commit/c1d7194e05c3798e2acc6a461247eb20e5d27a0a

RE: PWM Spike on starting/stopping on all channels

marcoster — Wed, 10 Sep 2025 09:44:48 GMT

Hi Sigurd,

thank you very much for the feedback - I just tested it myself and it looks great now!

Do you have any idea what change fixed this? Just out of curiosity!

Best regards
Marco

RE: PWM Spike on starting/stopping on all channels

Sigurd — Wed, 10 Sep 2025 09:04:12 GMT

Hi Marco,

Could you try with NCS v3.1.0, and see if the issue is solved there?

I'm seeing some strange spikes with NCS 3.0.2, but not with NCS 3.1.0

NCS 3.0.2

NCS 3.1.0

BR,

Sigurd

RE: PWM Spike on starting/stopping on all channels

marcoster — Tue, 19 Aug 2025 11:57:31 GMT

Hi there,
another Update from my side - I have a minimal test-project to test this attached to this post.

I also tested this on an nRF52840 and I can still see a small spike, although it does only get up to about 0.3V.

Here a screenshot of the nRF52840 result from the testproject:

And from the nRF54L15:

Note that Channel 2 is set to 500mV/div to better see the spike especially on the nRF52840.

I also just realized, that the dts-overlay on the nRF52840 probably doesn't deactivate polarity-inversion - so this might be the reason for different default pin-level on Channel 1.

devzone.nordicsemi.com/.../pwm_5F00_spike_5F00_test.zip

The code was tested on:

nRF52840-DK (1.0.0)
nRF54L15-DK (0.9.2)

Hope this helps to reproduce this!

Best regards
Marco

RE: PWM Spike on starting/stopping on all channels

marcoster — Tue, 19 Aug 2025 07:18:17 GMT

Forgot this in the example-code:

static const struct gpio_dt_spec m_motor_common_lowside = GPIO_DT_SPEC_GET(DT_NODELABEL(motor_common_lowside), gpios);
static const struct gpio_dt_spec m_motor1_minus_lowside = GPIO_DT_SPEC_GET(DT_NODELABEL(motor1_minus_lowside), gpios);

static const struct pwm_dt_spec m_motor_common_highside = PWM_DT_SPEC_GET(DT_NODELABEL(motor_common_highside));
static const struct pwm_dt_spec m_motor1_minus_highside = PWM_DT_SPEC_GET(DT_NODELABEL(motor1_minus_highside));

struct hbridge_pair {
    const struct pwm_dt_spec  *active_pwm;
    const struct pwm_dt_spec  *inactive_pwm;
    const struct gpio_dt_spec *active_gpio;
    const struct gpio_dt_spec *inactive_gpio;
};

static const struct hbridge_pair m_bridge_pairs[NUM_MOTOR_DRIVE] = {
    [MOTOR_DRIVE_LEFT]  = { .active_pwm = &m_motor1_minus_highside, .active_gpio = &m_motor_common_lowside, .inactive_pwm = &m_motor_common_highside, .inactive_gpio = &m_motor1_minus_lowside },
    [MOTOR_DRIVE_RIGHT] = { .active_pwm = &m_motor_common_highside, .active_gpio = &m_motor1_minus_lowside, .inactive_pwm = &m_motor1_minus_highside, .inactive_gpio = &m_motor_common_lowside },
};