DISPLAY_PWM

This section introduces the display PWM APIs including terms and acronyms, supported features, software architecture, details on how to use this API, PWM function groups, all enumerations, structures and functions. More...

Overview

This section introduces the display PWM APIs including terms and acronyms, supported features, software architecture, details on how to use this API, PWM function groups, all enumerations, structures and functions.

Terms and acronyms

Terms	Details
PWM	Pulse-width modulation is a modulation technique to encode a message into a pulsing signal. The duty cycle percentage for backlight brightness is used. For more information, please refer to Pulse-width modulation and Duty cycle in Wikipedia.

Supported features

• Support 26MHz and 104MHz input clock.
  The input clock can be set to 26MHz or 104MHz
  • 26MHz : If the input clock is set to 26MHz, the PWM output clock will be 25.39KHz (26MHz/1024).
  • 104MHz : If the input clock is set to 104MHz, the PWM output clock will be 101.5KHz (104MHz/1024).
• Support 10bits resolution.
  The resolution of display PWM is 10 bits which means the backlight has 1024 levels.

How to use this driver

• Use the PWM with 26MHz input clock and generate a 80% duty cycle PWM signal.
  
  • Step1: Call hal_display_pwm_init() to initialize the PWM hardware.
  • Step2: Call hal_display_pwm_set_duty() or hal_display_pwm_set_width() to set the PWM output duty cycle.
  • sample code:

    ret = hal_display_pwm_init(HAL_DISPLAY_PWM_CLOCK_26MHZ);
    if (HAL_DISPLAY_PWM_STATUS_OK != ret) {
        // error handle
    }
    
    // Configure the PWM to generate 80% duty cycle PWM signal.
    ret = hal_display_pwm_set_duty(80);
    if (HAL_DISPLAY_PWM_STATUS_OK != ret) {
        // error handle
    }

Functions
hal_display_pwm_status_t	hal_display_pwm_init (hal_display_pwm_clock_t clock)
	This function initializes the display PWM hardware. More...
hal_display_pwm_status_t	hal_display_pwm_deinit (void)
	This function de-initializes the display PWM hardware. More...
hal_display_pwm_status_t	hal_display_pwm_set_clock (hal_display_pwm_clock_t clock)
	This function sets the input clock of the PWM hardware. More...
hal_display_pwm_status_t	hal_display_pwm_set_duty (uint8_t percentage)
	This function sets the PWM duty cycle in percentage. More...
hal_display_pwm_status_t	hal_display_pwm_set_width (uint32_t width)
	This function sets the PWM duty cycle in integer format. More...

Modules
	Enum

Function Documentation

hal_display_pwm_status_t hal_display_pwm_deinit

(

void

)

This function de-initializes the display PWM hardware.

Returns

To indicate whether this function call is successful or not. HAL_DISPLAY_PWM_STATUS_OK, the operation completed successfully. HAL_DISPLAY_PWM_STATUS_INVALID_PARAMETER, the parameter needs to be verified. The parameter is out of bound. HAL_DISPLAY_PWM_STATUS_ERROR, an error occurred.

hal_display_pwm_status_t hal_display_pwm_init

(

hal_display_pwm_clock_t

clock

)

This function initializes the display PWM hardware.

Parameters

[in]

clock

specifies the input clock source, please refer to hal_display_pwm_clock_t.

Returns

To indicate whether this function call is successful or not. HAL_DISPLAY_PWM_STATUS_OK, the operation completed successfully. HAL_DISPLAY_PWM_STATUS_INVALID_PARAMETER, the parameter needs to be verified. The parameter is out of bound. HAL_DISPLAY_PWM_STATUS_ERROR, an error occurred.

hal_display_pwm_status_t hal_display_pwm_set_clock

(

hal_display_pwm_clock_t

clock

)

This function sets the input clock of the PWM hardware.

Parameters

[in]

clock

specifies the input clock source, please refer to hal_display_pwm_clock_t

Returns

To indicate whether this function call is successful or not. HAL_DISPLAY_PWM_STATUS_OK, the operation completed successfully. HAL_DISPLAY_PWM_STATUS_INVALID_PARAMETER, the parameter needs to be verified. The parameter is out of bound. HAL_DISPLAY_PWM_STATUS_ERROR, an error occurred.

hal_display_pwm_status_t hal_display_pwm_set_duty

(

uint8_t

percentage

)

This function sets the PWM duty cycle in percentage.

Parameters

[in]

percentage

represents the percentage of high width of output PWM signal. If it is 0, the output PWM signal will always stay on low. If it is 100, the output PWM signal will always stay on high and the backlight will be the brightest.

Returns

To indicate whether this function call is successful or not. HAL_DISPLAY_PWM_STATUS_OK, the operation completed successfully. HAL_DISPLAY_PWM_STATUS_INVALID_PARAMETER, the parameter needs to be verified. The parameter is out of bound. HAL_DISPLAY_PWM_STATUS_ERROR, an error occurred.

hal_display_pwm_status_t hal_display_pwm_set_width

(

uint32_t

width

)

This function sets the PWM duty cycle in integer format.

Parameters

[in]

width

represents the actual width of high width of output PWM signal. The range of the width is between 0 and 1024.

Returns

To indicate whether this function call is successful or not. HAL_DISPLAY_PWM_STATUS_OK, the operation completed successfully. HAL_DISPLAY_PWM_STATUS_INVALID_PARAMETER, the parameter needs to be verified. The parameter is out of bound. HAL_DISPLAY_PWM_STATUS_ERROR, an error occurred.