ACCDET

This section describes the programming interfaces of accessory detector (ACCDET) HAL driver. More...

Overview

This section describes the programming interfaces of accessory detector (ACCDET) HAL driver.

The hardware ACCDET detects the status of an earphone (plug-in/plug-out/hook-key), based on the suggested circuit. The de-bounce scheme is also supported to resist uncertain input noises. When the state is stable, the Pulse Width Modulation (PWM) unit of ACCDET enables the voltage of the comparator periodically to detect the plugging state. Very low-power consumption can be achieved if the detection feature is enabled and the PWM settings are defined according to the needs of the hardware being controlled. In order to compensate the delay between the detection login and comparator, the delay enabling scheme is adopted. Given the suitable delay number compared to the rising edge of PWM high pulse, the stable plugging state can be prorogated to digital detection logic. Then the correct plugging state can be detected and reported.

Terms and acronyms

The following provides descriptions to the terms commonly used in the ACCDET driver and how to use its various functions.

Terms	Details
ACCDET	Accessory detector is designed to detect the status of earphone (plug-in/plug-out/hook-key).
PWM	Pulse Width Modulation (PWM) is a modulation technique that encodes a message into a pulsing signal. The main use is to allow the control of the power supplied to electrical devices, especially to inertial loads such as motors. For more information, please refer to introduction to PWM in Wikipedia.

For PWM, the term duty cycle describes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on.

Supported features

As described above, to perform an accurate detection, the debounce time and proper PWM settings are supported. The supported features of ACCDET driver are listed below:

• Set debounce time separately for plug-in/plug-out/hook-key.
  The API dedicated for debounce time setting is hal_accdet_set_debounce_time(), and the parameter is of type hal_accdet_debounce_time_t. The parameters included are accdet_plug_in_debounce, accdet_plug_out_debounce and accdet_hook_key_debounce. User can adjust the three fields according to the sensitivity of the specific hardware circuit.
• Callback function registration.
  If the state of the plugged earphone is changed, an interrupt is triggered. Users could register their own callback function, by calling hal_accdet_register_callback(). The registered callback function is invoked in the ACCDET ISR routine once an interrupt is triggered.

How to use this driver

• Configure ACCDET module for earphone detection.
  Before the ACCDET module is enabled for earphone detection, user should configure the debounce time for all three states, and the callback function should be registered as well. The function hal_accdet_set_debounce_time() could be called anytime, to adjust the debounce time to a proper value, as shown in the following steps.
  • Step1: Call hal_accdet_init() to initialize the ACCDET module.
  • Step2: Call hal_accdet_set_debounce_time() to set debounce time separately for plug-in/plug-out/hook-key.
  • Step3: Call hal_accdet_register_callback() to register a callback function.
  • Step4: Call hal_accdet_enable() to enable the ACCDET module.
  • Step5: Call hal_accdet_disable() to disable the ACCDET module.
  • Step6: Call hal_accdet_deinit() to deinitialize the ACCDET module.
  • sample code:

    #define HOOK_KEY_DEBOUNCE_TIME  300//Hook key debounce is 300ms
    #define PLUG_IN_DEBOUNCE_TIME   500//Plug in debounce is 500ms
    #define PLUG_OUT_DEBOUNCE_TIME  50//plug out debounce is 50ms
    
    hal_accdet_debounce_time_t accdet_debounce;
    uint32_t user_data;
    
    accdet_debounce.accdet_hook_key_debounce = HOOK_KEY_DEBOUNCE_TIME;//Set debounce time for hook key
    accdet_debounce.accdet_plug_in_debounce = PLUG_IN_DEBOUNCE_TIME;//Set debounce time for plug in
    accdet_debounce.accdet_plug_out_debounce = PLUG_OUT_DEBOUNCE_TIME;//Set debounce time for plug out
    
    hal_accdet_init();//Initialize the ACCDET module
    hal_accdet_set_debounce_time(&debounce_time);//Set debounce time for ACCDET
    hal_accdet_register_callback(accdet_user_callback, (void *)&user_data);//Register a callback function
    hal_accdet_enable();//Enable ACCDET
    
    hal_accdet_disable();//Disable the ACCDET module
    hal_accdet_deinit();//Deinitialize the ACCDET module

    // Callback function. This function should be registered with #hal_accdet_register_callback.
    void accdet_user_callback(hal_accdet_callback_event_t event, void *user_data);
    {
          switch (event) {
              case HAL_ACCDET_EVENT_HOOK_KEY:
                  //user's handler
                  //break;
              case HAL_ACCDET_EVENT_PLUG_IN:
                 // user's handler
                 // break;
              case HAL_ACCDET_EVENT_PLUG_OUT:
                 // user's handler
                 // break;
              default:
                 // user's handler
                 // break;
           }
    }

Functions
hal_accdet_status_t	hal_accdet_init (void)
	ACCDET initialize function. More...
hal_accdet_status_t	hal_accdet_deinit (void)
	ACCDET deinitialization function. More...
hal_accdet_status_t	hal_accdet_enable (void)
	ACCDET enable function. More...
hal_accdet_status_t	hal_accdet_disable (void)
	ACCDET disable function. More...
hal_accdet_status_t	hal_accdet_register_callback (hal_accdet_callback_t accdet_callback, void *user_data)
	register callback function for ACCDET interrupt. More...
hal_accdet_status_t	hal_accdet_set_debounce_time (const hal_accdet_debounce_time_t *debounce_time)
	set debounce time for the ACCDET. More...

Modules
	Enum
	Struct
	Typedef

Function Documentation

hal_accdet_status_t hal_accdet_deinit

(

void

)

ACCDET deinitialization function.

Returns

HAL_ACCDET_STATUS_OK, ACCDET module is successfully deinitialized.

hal_accdet_status_t hal_accdet_disable

(

void

)

ACCDET disable function.

Disable the ACCDET module.

Returns

HAL_ACCDET_STATUS_OK, ACCDET module is successfully disabled.

hal_accdet_status_t hal_accdet_enable

(

void

)

ACCDET enable function.

Enable the ACCDET module.

Returns

HAL_ACCDET_STATUS_OK, ACCDET module is successfully enabled.

hal_accdet_status_t hal_accdet_init

(

void

)

ACCDET initialize function.

Returns

HAL_ACCDET_STATUS_ERROR_BUSY, ACCDET is busy.
HAL_ACCDET_STATUS_OK, ACCDET module is successfully initialized.

hal_accdet_status_t hal_accdet_register_callback	(	hal_accdet_callback_t	accdet_callback,
		void *	user_data
	)

register callback function for ACCDET interrupt.

Parameters

[in]	accdet_callback	is the pointer to the ACCDET callback function.
[in]	user_data	is the user data of callback function.

Returns

HAL_ACCDET_STATUS_OK, the callback function of the ACCDET is registered successfully.
HAL_ACCDET_STATUS_INVALID_PARAMETER, accdet_callback is NULL.

hal_accdet_status_t hal_accdet_set_debounce_time

(

const hal_accdet_debounce_time_t *

debounce_time

)

set debounce time for the ACCDET.

Parameters

[in]

debounce_time

is pointer of the debounce value structure of ACCDET, the unit of debounce is millisecond.

Returns

HAL_ACCDET_STATUS_OK, the debounce time of ACCDET is set successfully.
HAL_ACCDET_STATUS_INVALID_PARAMETER, debounce_time is NULL.