How can I trigger ADC with an external clock generator?

[ADynr.1]

Hello,

I'm trying to trigger ADC on the STM32F303RE Nucleo board with an external clock generator. Without external trigger settings, it works. I changed the trigger source to Timer8, then in TIM8 settings, I chose External Clock Source. What am I doing wrong? I didn't change any user codes, should I add pin up/down commands to start ADC in user code sections?

My ADC(DMA) and TIM8 settings:

(My clock(square wave) generator connected to PB6 pin)

[S.Ma]

If the goal is to trigger an ADC sample conversion, the ADC uses the internal clock AND a GPIO as triggering a conversion which is fed by the external clock.

Use a DMA to store the ADC results into a cyclic RAM array so you can see easily what's happening with less SW coding.

[ADynr.1]

I save the data to a size of 12000 buffer, then write in serial port. Without external trigger settings, it works. But, when I change "Continous Conversion Mode-Disable, External Trigger Source-Timer8", it doesn't work.

Briefly, the code I use(some of the variables are for saving to an SD card):

#define ADC_BUF_LEN 12000
 
void myprintf(const char *fmt, ...) {
  static char buffer[ADC_BUF_LEN];
  va_list args;
  va_start(args, fmt);
  vsnprintf(buffer, sizeof(buffer), fmt, args);
  va_end(args);
 
  int len = strlen(buffer);
  HAL_UART_Transmit(&huart2, (uint64_t*)buffer, len, -1);
 
}
 
HAL_ADC_Start_DMA(&hadc1, (uint16_t*)adc_buf, ADC_BUF_LEN);
 
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc) {
	for (int i = 0; i < ADC_BUF_LEN; ) {
	myprintf("%i\r\n", adc_buf[i]);
	i++;
	}