Firefly-RK3128 Buy Specs

Quad-core Cortex-A7 open source board,frequency up to 1.3GHz, integrated Mali-400 MP2 graphics processors, support OpenGL ES1.1/2.0, embedded high-performance 2D hardware acceleration, and can achieve 1080P H.265 video decoding and H.264 video coding.

PWM

Update time:2018-04-17 Views:2225

Firefly-RK3128 development board has 4 PWMs, namely PWM0 ~ PWM3:

  • PWM0/GPIO0_D2: exported in the extension board

  • PWM1/GPIO0_D3: used as AUX_DET signal internally

  • PWM2/GPIO0_D4: used as RTC_INT signal internally

  • PWM3: used by infrared transceivers

This article describes how to configure and use PWM.

The PWM driver file of FirePrime is:

kernel/drivers/pwm/pwm-rockchip.c

    Configuration steps

    You can follow these steps to finish the PWM configuration.

    Create PWM DTS Node

    PWM device nodes are defined in file kernel/arch/arm/boot/dts/rk312x.dtsi:

            pwm0: pwm@20050000 {compatible = "rockchip,rk-pwm";reg = <0x20050000 0x10>;#pwm-cells = <2>;pinctrl-names = "default";pinctrl-0 = <&pwm0_pin>;clocks = <&clk_gates7 10>;clock-names = "pclk_pwm";status = "disabled";}; 
            pwm1: pwm@20050010 {compatible = "rockchip,rk-pwm";reg = <0x20050010 0x10>;#pwm-cells = <2>;pinctrl-names = "default";pinctrl-0 = <&pwm1_pin>;clocks = <&clk_gates7 10>;clock-names = "pclk_pwm";status = "disabled";}; 
            pwm2: pwm@20050020 {compatible = "rockchip,rk-pwm";reg = <0x20050020 0x10>;#pwm-cells = <2>;pinctrl-names = "default";pinctrl-0 = <&pwm2_pin>;clocks = <&clk_gates7 10>;clock-names = "pclk_pwm";status = "disabled";}; 
            pwm3: pwm@20050030 {compatible = "rockchip,rk-pwm";reg = <0x20050030 0x10>;#pwm-cells = <2>;pinctrl-names = "default";pinctrl-0 = <&pwm3_pin>;clocks = <&clk_gates7 10>;clock-names = "pclk_pwm";status = "disabled";}; 
            remotectl: pwm@20050030 {compatible = "rockchip,remotectl-pwm";reg = <0x20050030 0x10>;#pwm-cells = <2>;pinctrl-names = "default";pinctrl-0 = <&pwm3_pin>;clocks = <&clk_gates7 10>;clock-names = "pclk_pwm";remote_pwm_id = <3>;interrupts = <GIC_SPI 30 IRQ_TYPE_LEVEL_HIGH>;status = "okay";};

    To use PWM0, you need to add to file kernel/arch/arm/boot/dts/rk3128-fireprime.dts:

           &pwm0 {
                   status = "okay";
           };

    Configure PWM driver

    The PWM driver is in file kernel/drivers/pwm/pwm-rockchip.c

    Control PWM Device

    Now you can use the PWM node created above to control devices, as shown in the following steps:

    (1). Include the pwm.h file

    #include <linux/pwm.h>

    This file includes the API functions of PWM.

    (2). Request PWM.

    You can use the pwm_request function to request the PWM device. For example:

    struct pwm_device * pwm0=NULL;pwm0= pwm_request(0, “backlight-pwm”);

    See The API of PWM device for more detail of this function.

    (3). Set PWM configuration

    You can use the function pwm_config to set the PWM configuration. For example:

    pwm_config(pwm0, 500000, 1000000);

    See The API of PWM device for more detail of this function.

    (4). Enable PWM

    Then you start the pwm device using the pwm_enable function. For example:

    int pwm_enable(struct pwm_device *pwm);

    See The API of PWM device for more detail of this function.

    The API of PWM device

    /**
     * pwm_request() - request a PWM device
     * @pwm_id: global PWM device index
     * @label: PWM device label
     *
     * This function is deprecated, use pwm_get() instead.
     */struct pwm_device *pwm_request(int pwm_id, const char *label);


    /**
     * pwm_free() - free a PWM device
     * @pwm: PWM device
     *
     * This function is deprecated, use pwm_put() instead.
     */void pwm_free(struct pwm_device *pwm);


    /**
     * pwm_config() - change a PWM device configuration
     * @pwm: PWM device
     * @duty_ns: "on" time (in nanoseconds)
     * @period_ns: duration (in nanoseconds) of one cycle
     */int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);


    /**
     * pwm_enable() - start a PWM output toggling
     * @pwm: PWM device
     */int pwm_enable(struct pwm_device *pwm);


    /**
     * pwm_disable() - stop a PWM output toggling
     * @pwm: PWM device
     */void pwm_disable(struct pwm_device *pwm);