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102 lines
4.7 KiB
Plaintext
102 lines
4.7 KiB
Plaintext
/**
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@page ADC_TriggerMode ADC3 conversion using Trigger Mode
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@verbatim
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******************************************************************************
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* @file ADC/ADC_TriggerMode/readme.txt
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* @author MCD Application Team
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* @brief Description of the ADC Trigger Mode example.
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******************************************************************************
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* @attention
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*
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* Copyright (c) 2016 STMicroelectronics.
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* All rights reserved.
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*
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* This software is licensed under terms that can be found in the LICENSE file
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* in the root directory of this software component.
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* If no LICENSE file comes with this software, it is provided AS-IS.
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*
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******************************************************************************
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@endverbatim
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@par Example Description
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How to use ADC3 and TIM2 to continuously convert data from an ADC channel.
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Each time an external trigger is generated by TIM2 a new conversion is started
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by the ADC.
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Each time an external trigger is generated by TIM2 a new conversion is started by ADC3.
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At the end of conversion, an interrupt is generated and the converted data of
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ADC3 DR register is affected to the uhADCxConvertedValue variable in the ADC
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conversion complete call back function (HAL_ADC_ConvCpltCallback).
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The timer is used to trigger an ADC measure at 20 KHz.
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Configuration of the timer to trig an ADC measure at 20 Khz:
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From the reference manual, Reset and Clock control part, Timer 2 is clocked on PCLK1.
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The function SystemClock_Config() configures the clock divider as follows:
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1) The system clock is 216 MHz.
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2) AHB Prescaler = 1 => AHB clock is 216 MHz.
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3) APB1 Prescaler = 4 => PCLK1 clock is 216 MHz/4.
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4) For Timer 2, as APB1 Prescaler = 4, Timer 2 Clock is PCLK1 clock X 2 = 216 MHz/2.
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For a 20 Khz frequency, we need (216 MHz/2) / 20 KHz = 5400 clock cycle.
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So, in TIM_Config function, we set the following period: htim.Init.Period = 5400;
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The voltage on pin PF.10 (ADC_CHANNEL_8)can vary using the board potentiometer RV1.
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The converted value is monitored through debugger: uhADCxConvertedValue variable.
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The uhADCxConvertedValue read value is coded on 12 bits, the Vref+ reference voltage is connected
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on the board to VDD (+3.3V), the Vref- reference voltage is connected on the board to the ground.
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To convert the read value in volts, here is the equation to apply :
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Voltage = uhADCxConvertedValue * (Vref+ - Vref-) / (2^12) = uhADCxConvertedValue * 3.3 / 4096
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Remark: LED3 is ON when there is an error in initialization.
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@par Keywords
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Analog, ADC, Analog to Digital, Trigger mode, Continuous conversion, Timer, Measurement, Voltage
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@Note<74>If the user code size exceeds the DTCM-RAM size or starts from internal cacheable memories (SRAM1 and SRAM2),that is shared between several processors,
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<20><><EFBFBD><EFBFBD><EFBFBD>then it is highly recommended to enable the CPU cache and maintain its coherence at application level.
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>The address and the size of cacheable buffers (shared between CPU and other masters) must be properly updated to be aligned to cache line size (32 bytes).
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@Note It is recommended to enable the cache and maintain its coherence, but depending on the use case
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> It is also possible to configure the MPU as "Write through", to guarantee the write access coherence.
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>In that case, the MPU must be configured as Cacheable/Bufferable/Not Shareable.
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Even though the user must manage the cache coherence for read accesses.
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Please refer to the AN4838 <20>Managing memory protection unit (MPU) in STM32 MCUs<55>
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<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Please refer to the AN4839 <20>Level 1 cache on STM32F7 Series<65>
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@par Directory contents
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- ADC/ADC_TriggerMode/Inc/stm32f7xx_hal_conf.h HAL configuration file
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- ADC/ADC_TriggerMode/Inc/stm32f7xx_it.h DMA interrupt handlers header file
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- ADC/ADC_TriggerMode/Inc/main.h Header for main.c module
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- ADC/ADC_TriggerMode/Src/stm32f7xx_it.c DMA interrupt handlers
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- ADC/ADC_TriggerMode/Src/main.c Main program
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- ADC/ADC_TriggerMode/Src/stm32f7xx_hal_msp.c HAL MSP file
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- ADC/ADC_TriggerMode/Src/system_stm32f7xx.c STM32F7xx system source file
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@par Hardware and Software environment
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- This example runs on STM32F756xx/STM32F746xx devices.
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- This example has been tested with STM327x6G-EVAL board revB and can be
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easily tailored to any other supported device and development board.
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- STM327x6G-EVAL revB Set-up
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- Use the Potentiometer (RV1) of the Eval board (connected to PF.10).
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- JP24 must be fitted in 1-2 positions
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@par How to use it ?
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In order to make the program work, you must do the following :
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- Open your preferred toolchain
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- Rebuild all files and load your image into target memory
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- Run the example
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*/
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