Simple PWM example

[Stefano1984]

Hi,

Is it possible to have a simple example of using PWM with the Zephyr?

With nRF5_SDK_17.1.0 I did this:

void Pwm1Init(void)
{
    ret_code_t err_code;

    nrf_pwm_sequence_t const    m_seq =
    {
        .values.p_individual = &pwm1Values,
        .length              = NRF_PWM_VALUES_LENGTH(pwm1Values),
        .repeats             = 0,
        .end_delay           = 0
    };

    nrf_drv_pwm_config_t const config0 =
    {
        .output_pins =
        {
            BUZZER_PIN | NRF_DRV_PWM_PIN_INVERTED,
	    LED_R | NRF_DRV_PWM_PIN_INVERTED,
	    LED_G | NRF_DRV_PWM_PIN_INVERTED,
	    LED_B | NRF_DRV_PWM_PIN_INVERTED,
        },
        .irq_priority = APP_IRQ_PRIORITY_LOWEST,
        .base_clock   = NRF_PWM_CLK_250kHz,
        .count_mode   = NRF_PWM_MODE_UP,
        .top_value    = 62,                      // PWM period 4032Hz, 62 -> Duty Cycle = 100%.
        .load_mode    = NRF_PWM_LOAD_INDIVIDUAL,
        .step_mode    = NRF_PWM_STEP_AUTO
    };

    err_code = nrf_drv_pwm_init(&m_pwm1, &config0, NULL);
    APP_ERROR_CHECK(err_code);

    pwm1Values.channel_0 = 0x8000;
    pwm1Values.channel_1 = 0x8000;
    pwm1Values.channel_2 = 0x8000;
    pwm1Values.channel_3 = 0x8000;

    nrf_drv_pwm_simple_playback(&m_pwm1, &m_seq, 1, NRF_DRV_PWM_FLAG_LOOP);
}

void Pwm1SetDutyCycle(uint8_t channel, uint16_t value)
{
    ((uint16_t *)(&pwm1Values))[channel] = (value | 0x8000);
}

I used the Pwm1SetDutyCycle function to set the Duty cycle of the 4 channels.
Now what do I do with the Zephyr? Can anyone give me an example? The examples I found didn't help me.

Thank you.

[AHaug]

Hi,

In lesson 4 in https://academy.nordicsemi.com/courses/nrf-connect-sdk-intermediate/ we have a course showcasing how to use the PWM API in Zephyr through nRF Connect SDK. I recommend that you have a look at this. The solution to the hands on in this lesson can be seen in github.com/.../lesson4.

Kind regards,
Andreas

[Stefano1984]

Thank you,
these lessons are very useful.
However, I notice that there is a lesson missing that deals with the TWI module.
I was still able to communicate via the I2C BUS but I can't set the clock frequency. In particular I want to set a frequency of 10 kHz but I don't know how.

I tried to do like this:

&i2c0 {
	status = "okay";
	pinctrl-0 = <&i2c0_default>;
	pinctrl-names = "default";
	clock-frequency = <10000>;
};

But it gives me the following error:

C:/ncs/v2.6.0-rc2/zephyr/include/zephyr/toolchain/gcc.h:87:36: error: static assertion failed: "Wrong I2C 0 frequency setting in dts"

Can you help me?

Thank you

[rajeev]

The i2c clock freq in zephyr needs to be set as such: 

I2C_BITRATE_FAST etc....

&i2c1 {
	compatible = "nordic,nrf-twim";
	status = "okay";
	clock-frequency = <I2C_BITRATE_FAST>;

	pinctrl-0 = <&i2c1_default>;
	pinctrl-1 = <&i2c1_sleep>;
	pinctrl-names = "default", "sleep";
};

See all those frequency settings here
https://docs.zephyrproject.org/apidoc/latest/dt-bindings_2i2c_2i2c_8h.html

[AHaug]

Hi,

TWI/I2C should be covered in lesson 6 in https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/

Kind regards,
Andreas

[Stefano1984]

HI,
I didn't understand how this solves my problem.
I2C_BITRATE_FAST corresponds to a frequency of 400 Kbit/s as specified in the i2c.h file:

#define I2C_BITRATE_STANDARD	100000	/* 100 Kbit/s */
#define I2C_BITRATE_FAST	400000	/* 400 Kbit/s */        <--------
#define I2C_BITRATE_FAST_PLUS	1000000 /* 1 Mbit/s */
#define I2C_BITRATE_HIGH	3400000	/* 3.4 Mbit/s */
#define I2C_BITRATE_ULTRA	5000000 /* 5 Mbit/s */

I need to go at a slower speed. I need a speed of 10 Kbit/s.

With nRF SDK I was able to do this by setting "frequency = 0x00290000UL".

void ext_twi_init(void)
{
    ret_code_t err_code;

    const nrf_drv_twi_config_t twi_config = {
       .scl                = EXT_SCL_PIN,
       .sda                = EXT_SDA_PIN,
       .frequency          = 0x00290000UL,      // = 10Kbit/s. <------------
       .interrupt_priority = APP_IRQ_PRIORITY_HIGH,
       .clear_bus_init     = false
    };

    err_code = nrf_drv_twi_init(&m_ext_twi, &twi_config, NULL, NULL);
    APP_ERROR_CHECK(err_code);

    nrf_drv_twi_enable(&m_ext_twi);
}

How do I do the same thing using Zephyr?

Thank you