STM32G431 ADC2 DMA causes MCU to hang while ADC1 DMA works fine

[shohanur00]

Hello everyone,

I am currently working with the STM32G431CBT6 and designing a custom ESC using the DRV8301 gate driver. My application requires a total of 9 ADC channels:

• ADC1 → 4 channels

• ADC2 → 5 channels

I configured both ADCs in independent mode with DMA (circular) using STM32CubeMX.

---

Issue Description

When I start ADC with DMA using the following function:

void ADC_Start_System(void)
{
    // 1. Calibration
    HAL_ADCEx_Calibration_Start(&hadc1, ADC_SINGLE_ENDED);
    HAL_ADCEx_Calibration_Start(&hadc2, ADC_SINGLE_ENDED);

    HAL_Delay(10);

    // 2. Start ADC1
    if (HAL_ADC_Start_DMA(&hadc1, (uint32_t*)adc1_buffer, 4) != HAL_OK)
        Error_Handler();

    // 3. Start ADC2
    if (HAL_ADC_Start_DMA(&hadc2, (uint32_t*)adc2_buffer, 5) != HAL_OK)
        Error_Handler();
}

Observed Behavior

• ADC1 + DMA works perfectly

• MCU gets stuck when calling:

HAL_ADC_Start_DMA(&hadc2, (uint32_t*)adc2_buffer, 5);

• No error returned, but CPU halts inside HAL (likely waiting on a flag)

---

What I Have Verified

• Calibration is performed before start

• DMA is configured in circular mode

• NVIC interrupts for DMA channels are enabled

• Separate DMA channels used for ADC1 and ADC2

• Buffers are correctly sized:

  uint16_t adc1_buffer[4];
  uint16_t adc2_buffer[5];

• Polling mode works fine for ADC2

• ADC mode is independent (not dual mode)

---

Additional Notes

• MCU: STM32G431CBT6

• Toolchain: STM32CubeMX + HAL

• Application: ESC (motor control)

• No external trigger (software start used)

• Continuous conversion mode enabled

---

Question

Why does HAL_ADC_Start_DMA() work for ADC1 but cause the MCU to hang for ADC2?

Is there any known limitation or special requirement for using ADC2 with DMA on STM32G4 (especially when ADC1 is already running with DMA)?

---

Any help or guidance would be greatly appreciated.

Thanks in advance!

[shohanur00]

[mƎALLEm]

You didn't set the break point at the right line.

I said in my previous post, set it at if(status != HAL_OK) / line 68

HAL_ADC_Start_DMA()  is not yet executed when you set the breakpoint at line 58!

[TDK]

If it's stuck in the call, good luck getting a breakpoint after the call to be hit.

As suggested before, let it run, hit pause, see where it's at. Probably in an interrupt. Probably because you're converting too quickly. Slow down the sample rate.

[shohanur00]

[mƎALLEm]

So, the status is OK for ADC2. 

I see in your code you're performing a direct access to the registers for ADC2:

Why is this?

[shohanur00]

I have written a bare metal function for testing , This is my bare metal function . Its working fine . I have not call this function during your test.

void ADC2_DMA_Start_BareMetal(void)

{

// 1. Disable DMA

DMA1_Channel2->CCR &= ~DMA_CCR_EN;

// 2. Setup DMA

DMA1_Channel2->CPAR = (uint32_t)&ADC2->DR;

DMA1_Channel2->CMAR = (uint32_t)adc2_buffer;

DMA1_Channel2->CNDTR = 5;

DMA1_Channel2->CCR =

DMA_CCR_MINC

| DMA_CCR_CIRC

| DMA_CCR_PSIZE_0

| DMA_CCR_MSIZE_0;

DMA1_Channel2->CCR |= DMA_CCR_EN;

// 3. Enable ADC DMA

ADC2->CFGR |= ADC_CFGR_DMAEN | ADC_CFGR_DMACFG;

// 4. Enable ADC

if (!(ADC2->CR & ADC_CR_ADEN))

{

ADC2->CR |= ADC_CR_ADEN;

while (!(ADC2->ISR & ADC_ISR_ADRDY));

}

// 5. Start conversion

ADC2->CR |= ADC_CR_ADSTART;

}