ADC Calibration Failure on STM32N657 Using ADC1 Channel 1

[dw1]

Dear STMicroelectronics Support Team,

I am encountering an issue with ADC calibration on the STM32N657 microcontroller. Despite multiple attempts, the calibration process consistently fails. Below are the details of my setup and observations for your reference:

Hardware Configuration:

• ADC: ADC1, Channel 1

• Reference Voltage:

  • VREF+: External 1.8V (measured 1.76V)

  • VREF-: Ground

• Other: Enabled ICache/DCache, GPIO, USART1, and system isolation.

Software Configuration:

• Initialization Code:

SCB_EnableICache();
SCB_EnableDCache();
HAL_Init();
MX_GPIO_Init();
MX_ADC1_Init();
MX_USART1_UART_Init();
SystemIsolation_Config();

// Debug: Check registers post-init
printf("Post-Init ADC_CR: 0x%08lX\r\n", hadc1.Instance->CR);  // Output: 0x00000000
printf("Post-Init ADC_ISR: 0x%08lX\r\n", hadc1.Instance->ISR); // Output: 0x00000000

// Explicit MSP init (debug)
HAL_ADC_MspInit(&hadc1);
printf("Post-MSP ADC_CR: 0x%08lX\r\n", hadc1.Instance->CR);    // Output: 0x00000000
printf("Post-MSP ADC_ISR: 0x%08lX\r\n", hadc1.Instance->ISR);  // Output: 0x00000000

// Attempt calibration
HAL_StatusTypeDef status = HAL_ADCEx_Calibration_Start(&hadc1, ADC_SINGLE_ENDED);
if (status != HAL_OK) {
    printf("Calibration Failed. CR: 0x%08lX, ISR: 0x%08lX\n", 
           hadc1.Instance->CR, hadc1.Instance->ISR); // CR: 0x00000001, ISR: 0x0000000B
    while(1);
}

• Observed Behavior:

  1. Register States:

     • After initialization,  and  remain , suggesting ADC is not enabled.ADC_CRADC_ISR0x00000000

     • Post-calibration failure:

       • ADC_CR = 0x00000001 (ADEN bit set, but no further activity).

       • ADC_ISR = 0x0000000B (Flags:  +  + ).ADRDYEOSEOC

  2. Calibration Outcome:

     • Always fails with .HAL_ERROR

  Questions:

  1. Why do  and  stay zero after initialization? Is the ADC not properly enabled?ADC_CRADC_ISR

  2. Could the external reference voltage (1.76V, slightly below nominal 1.8V) cause calibration failure?

  3. Are there known errata or configuration steps specific to STM32N657 for ADC calibration?

  Additional Context:

  • CubeMX Configuration:

    • Single-ended mode, 12-bit resolution, software trigger.

    • No DMA/IRQ, scan mode disabled.

  • Troubleshooting Attempts:

    • Verified clock configuration (ADC clock ≤ max limit).

    • Checked VDDA/VREF+ stability with oscilloscope.

  I would greatly appreciate any insights or suggestions to resolve this issue. Please let me know if further details are required.

  Best regards,
  dw1