PWM REFERENCE

1. PWM Parameters¶

1.1. Duty_cycle¶

• Duty cycle

  Echo 25 > duty_cycle means that the duty cycle is 25%.

1.2. Period¶

• Frequency

  Echo 2000 > period

  It represents a pwm wave with a frequency of 2kHz.

1.3. Enable/disable¶

• Enable

1.4. Polarity¶

• Polarity

  If it is normal. Then duty_cycle=25%, which means that the proportion of high level is 25%.

  If it is inverse, it is the opposite of the above.

2. Kernel Config¶

2.1. dts Config¶

Fig 2-1

npwm: 4 —— means there are 4 groups of pwm;

Pad-ctrl: Configure 4 groups of pads to be PWM. If 4 groups are not required, the corresponding value of pad can be set to PAD_UNKNOWN. Since gpio is shared, when gpio is used as pwm, the driver will automatically switch the pad

Like Display Demo Board：

Add the followings to Infinity2m-ssc011a-s01a.dtsi：

pwm {

    compatible = "sstar,infinity-pwm";

    reg = <0x1F003400 0x600>;

    clocks = <&CLK_xtali_12m>;

    npwm = <2>;

    pad-ctrl = <PAD_GPIO4 PAD_GPIO5>;

    status = "ok"; // no available pads

};

PAD_GPIO4->PWM0 PAD_GPIO5->PWM1

nfinity2m-ssc011a-s01a-padmux.dtsi

Modify：

<PAD_GPIO4 PINMUX_FOR_PWM0_MODE_3 MDRV_PUSE_PWM0 >,

<PAD_GPIO5 PINMUX_FOR_PWM1_MODE_4 MDRV_PUSE_PWM1 >;

Kernel config：

Fig 2-2

3. Hardware Examples¶

Fig 3-1

Fig 3-2

Configure dts by check: drivers\sstar\include\infinity2m\gpio.h

4. PWM Architecture¶

Fig 4-1

5. User Mode Control Of PWM¶

Corresponding user layer code:

which is:

Open a node;

Write a node.