STM32G4 series ADC acquisition and configuration

 The STM32G4 series features high-performance ADC peripherals that can be configured for a wide range of applications—from basic single-channel measurements to advanced multi-channel, high-speed acquisition using DMA and external triggers. Here’s an overview of how to approach ADC acquisition and configuration on these devices:

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1. ADC Initialization and Clock Setup

• Clock Configuration:
  Ensure that the ADC clock is correctly configured. The ADC clock is derived from the system clock, and you must choose an appropriate prescaler to balance conversion speed and accuracy. This is typically done in your clock configuration setup (using STM32CubeMX or manually in your code).

• Peripheral Enablement:
  Before configuring the ADC, enable its clock in the RCC registers.

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2. ADC Configuration Using HAL or LL Libraries

You can configure the ADC either using the high-level HAL (Hardware Abstraction Layer) or the LL (Low Level) drivers. Below is an example using the HAL library.

Basic ADC Configuration Example (HAL):

c

ADC_HandleTypeDef hadc1;
ADC_ChannelConfTypeDef sConfig = {0};

// ADC Instance and Initialization
hadc1.Instance = ADC1;
hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV2;  // Adjust based on system clock
hadc1.Init.Resolution = ADC_RESOLUTION_12B;            // 12-bit resolution (other options available)
hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;            // Single channel conversion; set to ENABLE for multi-channel
hadc1.Init.ContinuousConvMode = ENABLE;                // Continuous conversion for ongoing acquisition
hadc1.Init.DiscontinuousConvMode = DISABLE;
hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;  // Software start
hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.NbrOfConversion = 1;                        // Number of channels in conversion sequence
hadc1.Init.DMAContinuousRequests = ENABLE;           // Enable if using DMA
hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;         // End of conversion flag per conversion

if (HAL_ADC_Init(&hadc1) != HAL_OK)
{
    // Handle error
    Error_Handler();
}

// ADC Calibration (if supported/needed)
if (HAL_ADCEx_Calibration_Start(&hadc1, ADC_SINGLE_ENDED) != HAL_OK)
{
    // Calibration error
    Error_Handler();
}

// Configure the ADC channel
sConfig.Channel = ADC_CHANNEL_1;                     // Select channel (e.g., ADC_CHANNEL_1)
sConfig.Rank = ADC_REGULAR_RANK_1;                     // Rank in the regular group sequence
sConfig.SamplingTime = ADC_SAMPLETIME_19CYCLES_5;      // Sampling time; adjust based on your signal and impedance

if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
{
    // Channel configuration error
    Error_Handler();
}

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3. Acquisition Techniques

• Software vs. Hardware Triggering:
  You can start conversions manually (software trigger) or configure the ADC to start conversions based on external events (hardware trigger) from timers or other peripherals.

• DMA for High-Speed Data Acquisition:
  For continuous or multi-channel acquisitions, DMA (Direct Memory Access) is highly recommended to transfer conversion data from the ADC to memory without burdening the CPU. For example:

  c
  
  // Define buffer and size according to your requirements
  #define ADC_BUFFER_SIZE  64
  uint32_t adcBuffer[ADC_BUFFER_SIZE];
  
  // Start ADC conversion using DMA
  if (HAL_ADC_Start_DMA(&hadc1, adcBuffer, ADC_BUFFER_SIZE) != HAL_OK)
  {
      // DMA start error
      Error_Handler();
  }
  

• Interrupts:
  If DMA is not required, you can use ADC interrupts to handle end-of-conversion events and process data as it becomes available.

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4. Optimizing ADC Performance

• Sampling Time Adjustment:
  The sample time must be long enough for the ADC’s internal sample-and-hold capacitor to charge, especially when measuring high-impedance sources. Experiment with different settings to find the best balance between conversion speed and accuracy.

• Oversampling and Averaging:
  The STM32G4 ADC can support oversampling modes to improve resolution and reduce noise. Configure oversampling settings if your application demands higher precision.

• Calibration and Linearization:
  Regular calibration helps minimize offset errors and improve measurement accuracy.

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5. Practical Considerations

• Board Layout:
  Good PCB design and proper analog signal routing are crucial for reducing noise and interference.

• Temperature Effects:
  Consider temperature calibration or compensation if your application operates in varying thermal environments.

• Use of STM32CubeMX:
  STM32CubeMX can generate initialization code for the ADC, easing configuration and ensuring proper clock and peripheral setups.

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This high-level overview should give you a solid foundation for setting up ADC acquisition on STM32G4 devices.