ADC

/**
  ******************************************************************************
  * @file    stm32f2xx_hal_adc.c
  * @author  MCD Application Team
  * @version V1.0.1
  * @date    25-March-2014
  * @brief   This file provides firmware functions to manage the following
  *          functionalities of the Analog to Digital Convertor (ADC) peripheral:
  *           + Initialization and de-initialization functions
  *           + IO operation functions
  *           + State and errors functions
  *
  @verbatim
  ==============================================================================
                    ##### ADC Peripheral features #####
  ==============================================================================
  [..]
  (#) 12-bit, 10-bit, 8-bit or 6-bit configurable resolution.
  (#) Interrupt generation at the end of conversion, end of injected conversion,
      and in case of analog watchdog or overrun events
  (#) Single and continuous conversion modes.
  (#) Scan mode for automatic conversion of channel 0 to channel x.
  (#) Data alignment with in-built data coherency.
  (#) Channel-wise programmable sampling time.
  (#) External trigger option with configurable polarity for both regular and
      injected conversion.
  (#) Dual/Triple mode (on devices with 2 ADCs or more).
  (#) Configurable DMA data storage in Dual/Triple ADC mode.
  (#) Configurable delay between conversions in Dual/Triple interleaved mode.
  (#) ADC conversion type (refer to the datasheets).
  (#) ADC supply requirements: 2.4 V to 3.6 V at full speed and down to 1.8 V at
      slower speed.
  (#) ADC input range: VREF(minus) = VIN = VREF(plus).
  (#) DMA request generation during regular channel conversion.


                     ##### How to use this driver #####
  ==============================================================================
    [..]
    (#)Initialize the ADC low level resources by implementing the HAL_ADC_MspInit():
       (##) Enable the ADC interface clock using __ADC_CLK_ENABLE()
       (##) ADC pins configuration
             (+++) Enable the clock for the ADC GPIOs using the following function:
                   __GPIOx_CLK_ENABLE()
             (+++) Configure these ADC pins in analog mode using HAL_GPIO_Init()
       (##) In case of using interrupts (e.g. HAL_ADC_Start_IT())
             (+++) Configure the ADC interrupt priority using HAL_NVIC_SetPriority()
             (+++) Enable the ADC IRQ handler using HAL_NVIC_EnableIRQ()
             (+++) In ADC IRQ handler, call HAL_ADC_IRQHandler()
      (##) In case of using DMA to control data transfer (e.g. HAL_ADC_Start_DMA())
             (+++) Enable the DMAx interface clock using __DMAx_CLK_ENABLE()
             (+++) Configure and enable two DMA streams stream for managing data
                 transfer from peripheral to memory (output stream)
             (+++) Associate the initilalized DMA handle to the CRYP DMA handle
                 using  __HAL_LINKDMA()
             (+++) Configure the priority and enable the NVIC for the transfer complete
                 interrupt on the two DMA Streams. The output stream should have higher
                 priority than the input stream.

     (#) Configure the ADC Prescaler, conversion resolution and data alignment
         using the HAL_ADC_Init() function.

     (#) Configure the ADC regular channels group features, use HAL_ADC_Init()
         and HAL_ADC_ConfigChannel() functions.

     (#) Three mode of operations are available within this driver :

     *** Polling mode IO operation ***
     =================================
     [..]
       (+) Start the ADC peripheral using HAL_ADC_Start()
       (+) Wait for end of conversion using HAL_ADC_PollForConversion(), at this stage
           user can specify the value of timeout according to his end application
       (+) To read the ADC converted values, use the HAL_ADC_GetValue() function.
       (+) Stop the ADC peripheral using HAL_ADC_Stop()

     *** Interrupt mode IO operation ***
     ===================================
     [..]
       (+) Start the ADC peripheral using HAL_ADC_Start_IT()
       (+) Use HAL_ADC_IRQHandler() called under ADC_IRQHandler() Interrupt subroutine
       (+) At ADC end of conversion HAL_ADC_ConvCpltCallback() function is executed and user can
            add his own code by customization of function pointer HAL_ADC_ConvCpltCallback
       (+) In case of ADC Error, HAL_ADC_ErrorCallback() function is executed and user can
            add his own code by customization of function pointer HAL_ADC_ErrorCallback
        (+) Stop the ADC peripheral using HAL_ADC_Stop_IT()

     *** DMA mode IO operation ***
     ==============================
     [..]
       (+) Start the ADC peripheral using HAL_ADC_Start_DMA(), at this stage the user specify the length
           of data to be transfered at each end of conversion
       (+) At The end of data transfer by HAL_ADC_ConvCpltCallback() function is executed and user can
            add his own code by customization of function pointer HAL_ADC_ConvCpltCallback
       (+) In case of transfer Error, HAL_ADC_ErrorCallback() function is executed and user can
            add his own code by customization of function pointer HAL_ADC_ErrorCallback
       (+) Stop the ADC peripheral using HAL_ADC_Stop_DMA()

     *** ADC HAL driver macros list ***
     =============================================
     [..]
       Below the list of most used macros in ADC HAL driver.

      (+) __HAL_ADC_ENABLE : Enable the ADC peripheral
      (+) __HAL_ADC_DISABLE : Disable the ADC peripheral
      (+) __HAL_ADC_ENABLE_IT: Enable the ADC end of conversion interrupt
      (+) __HAL_ADC_DISABLE_IT: Disable the ADC end of conversion interrupt
      (+) __HAL_ADC_GET_IT_SOURCE: Check if the specified ADC interrupt source is enabled or disabled
      (+) __HAL_ADC_CLEAR_FLAG: Clear the ADC's pending flags
      (+) __HAL_ADC_GET_FLAG: Get the selected ADC's flag status
      (+) __HAL_ADC_GET_RESOLUTION: Return resolution bits in CR1 register

     [..]
       (@) You can refer to the ADC HAL driver header file for more useful macros

    @endverbatim
  ******************************************************************************
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  *
  *
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  ******************************************************************************
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