RE: Updating PWM sequence in NCS using nrfx driver

Einar Thorsrud — Tue, 17 Dec 2024 13:24:58 GMT

Hi,

I am sorry for the delay. Continuing in your private support ticket for now as that has updated information.

RE: Updating PWM sequence in NCS using nrfx driver

Haresh05 — Fri, 13 Dec 2024 13:55:59 GMT

I know it should work and same thing is working on nrf52832 with sdk13. So it should work with nrf52840 with NCS.

But strange thing is I am not even getting the sequence completion interrupt when I increase the frequency.

Sharing the example code I am using and the output I am getting

#include <zephyr/kernel.h>
#include <nrfx_pwm.h>
#include <hal/nrf_gpio.h> // Required for NRF_GPIO_PIN_MAP

#define PWM_OUTPUT_PIN  NRF_GPIO_PIN_MAP(1, 13) // Port 1, Pin 13
#define LED0_PIN        NRF_GPIO_PIN_MAP(0, 13) // LED1 pin
#define LED1_PIN        NRF_GPIO_PIN_MAP(0, 14) // LED1 pin
#define LED2_PIN        NRF_GPIO_PIN_MAP(0, 15) // LED1 pin

#define PWM_TOP_VALUE               1000
#define PWM_INST_IDX                0
#define DIGITAL_BYTES_PER_WRITE     24
#define MULTIPLY_FACTOR             1

static nrfx_pwm_t pwm_instance = NRFX_PWM_INSTANCE(0);
static nrf_pwm_values_common_t pwm_values[DIGITAL_BYTES_PER_WRITE * MULTIPLY_FACTOR] = {
    [0 ... (DIGITAL_BYTES_PER_WRITE * MULTIPLY_FACTOR) - 1] = PWM_TOP_VALUE / 2
};

static nrf_pwm_sequence_t pwm_seq0 = {
    .values.p_common = pwm_values,
    .length = NRF_PWM_VALUES_LENGTH(pwm_values),
    .repeats = 0,
    .end_delay = 0,
};

static nrf_pwm_sequence_t pwm_seq1 = {
    .values.p_common = pwm_values,
    .length = NRF_PWM_VALUES_LENGTH(pwm_values),
    .repeats = 0,
    .end_delay = 0,
};

static void pwm_interrupt_callback(nrfx_pwm_evt_type_t event_type, void *context) {
    if (event_type == NRFX_PWM_EVT_END_SEQ0) {
        printf("NRFX_PWM_EVT_END_SEQ0 triggered\n");
    }
    if (event_type == NRFX_PWM_EVT_END_SEQ1) {
        printf("NRFX_PWM_EVT_END_SEQ1 triggered\n");
    }
}

void main(void)
{
    nrfx_pwm_config_t pwm_config = NRFX_PWM_DEFAULT_CONFIG(PWM_OUTPUT_PIN, LED0_PIN, LED1_PIN,LED2_PIN);
    //pwm_config.base_clock = NRF_PWM_CLK_16MHz;
    pwm_config.output_pins[0] = PWM_OUTPUT_PIN;
    pwm_config.top_value = PWM_TOP_VALUE;

 #if defined(__ZEPHYR__)
    IRQ_CONNECT(NRFX_IRQ_NUMBER_GET(NRF_PWM_INST_GET(PWM_INST_IDX)), IRQ_PRIO_LOWEST,
                NRFX_PWM_INST_HANDLER_GET(PWM_INST_IDX), 0, 0);
#endif

   if (nrfx_pwm_init(&pwm_instance, &pwm_config, pwm_interrupt_callback, NULL) != NRFX_SUCCESS) {
        printk("PWM initialization failed\n");
        return;
    }

    printk("PWM initialized\n");
    nrfx_pwm_complex_playback(&pwm_instance, &pwm_seq0, &pwm_seq1, 8, 
            NRFX_PWM_FLAG_SIGNAL_END_SEQ0 | NRFX_PWM_FLAG_SIGNAL_END_SEQ1 | NRFX_PWM_FLAG_STOP);
    while (1) {
        k_sleep(K_MSEC(5000));
    }
}

For this I am getting following output

[2024-12-13 19:12:39.341] *** Booting nRF Connect SDK v2.7.0-5cb85570ca43 ***
[2024-12-13 19:12:39.344] *** Using Zephyr OS v3.6.99-100befc70c74 ***
[2024-12-13 19:12:39.348] PWM initialized
[2024-12-13 19:12:39.374] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:12:39.398] NRFX_PWM_EVT_END_SEQ1 triggered
[2024-12-13 19:12:39.422] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:12:39.446] NRFX_PWM_EVT_END_SEQ1 triggered
[2024-12-13 19:12:39.469] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:12:39.493] NRFX_PWM_EVT_END_SEQ1 triggered
[2024-12-13 19:12:39.517] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:12:39.541] NRFX_PWM_EVT_END_SEQ1 triggered
[2024-12-13 19:12:39.565] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:12:39.589] NRFX_PWM_EVT_END_SEQ1 triggered
[2024-12-13 19:12:39.613] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:12:39.637] NRFX_PWM_EVT_END_SEQ1 triggered
[2024-12-13 19:12:39.661] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:12:39.685] NRFX_PWM_EVT_END_SEQ1 triggered
[2024-12-13 19:12:39.709] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:12:39.733] NRFX_PWM_EVT_END_SEQ1 triggered

Now if I change the PWM_TOP_VALUE to 28 and set the clock to 16MHz, I am getting following output

[2024-12-13 19:13:33.322] *** Booting nRF Connect SDK v2.7.0-5cb85570ca43 ***
[2024-12-13 19:13:33.326] *** Using Zephyr OS v3.6.99-100befc70c74 ***
[2024-12-13 19:13:33.330] PWM initialized
[2024-12-13 19:13:33.332] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:13:33.335] NRFX_PWM_EVT_END_SEQ0 triggered
[2024-12-13 19:13:33.337] NRFX_PWM_EVT_END_SEQ1 triggered

In My understanding this should have worked but not sure what is wrong in this.

Please let me know if I have configured something incorrectly or what changes should I do to make it work.

RE: Updating PWM sequence in NCS using nrfx driver

Einar Thorsrud — Fri, 13 Dec 2024 13:35:27 GMT

Hi,

The dequence pointers are double buffered, so there should normally not be a problem with higher data rate either. That said, LED strip control is often doen usint the I2S peripheral which while not designed for it, is well suited.