STM32F4 ADC Injected and DMA.

I don't think so. It doesn't have any specific DMA channel committed to such, and having it in the primary stream would just tend to cause all kinds of chaos in the data array. The point of injecting is to get some out-of-band conversions done.

Ok, so you said that I can do a regular dual interleaved ADC1+ADC2 and use the ADC3 in regular mode?  I tried but like in another post the status register was always busy

On paper it looks viable, I've done independent DMA on 3 ADC channels. I can't make a business case to prototype the solution here, and definitely not with the HAL.

I've used ADC1+ADC2 paired in DMA mode and ADC3 injected in interrupt mode, works fine. Since injected conversions are out of band you can't use DMA as it would trash your conversion buffers. All you have to do is set up ADC3 JEOC interrupt and read the injected conversion when the interrupt occurs.

// power supply injected conversion, open AWD windows for all ADCs after debounce 
if(ADC_GetITStatus(ADC3, ADC_IT_JEOC) != RESET) 
{ // ADC3 injected conversion ready 
ADC_ClearITPendingBit(ADC3, ADC_IT_JEOC); // clear JEOC interrupt 
ADC_ClearFlag(ADC3, ADC_FLAG_JSTRT | ADC_FLAG_JEOC); 
adcInjects[ADC_IOB_MISC]++; // count ADC injections 
adcSample[ADCDEV_CHAN_POWER] = 
ADC_GetInjectedConversionValue(ADC3, ADC_InjectedChannel_1); // 24V power supply

I think I have found the problem. I am using the HAL STM32F4 Library. If you look at the function to start an injected conversion with interrupt you must use the ADC1 for the injection (last if block of the function).

HAL_StatusTypeDef HAL_ADCEx_InjectedStart_IT(ADC_HandleTypeDef* hadc)
{
__IO uint32_t counter = 0;
uint32_t tmp1 = 0, tmp2 =0;
/* Process locked */
__HAL_LOCK(hadc);
/* Check if a regular conversion is ongoing */
if(hadc->State == HAL_ADC_STATE_BUSY_REG)
{
/* Change ADC state */
hadc->State = HAL_ADC_STATE_BUSY_INJ_REG; 
}
else
{
/* Change ADC state */
hadc->State = HAL_ADC_STATE_BUSY_INJ;
}
/* Set ADC error code to none */
hadc->ErrorCode = HAL_ADC_ERROR_NONE;
/* Check if ADC peripheral is disabled in order to enable it and wait during 
Tstab time the ADC's stabilization */
if((hadc->Instance->CR2 & ADC_CR2_ADON) != ADC_CR2_ADON)
{ 
/* Enable the Peripheral */
__HAL_ADC_ENABLE(hadc);
/* Delay for temperature sensor stabilization time */
/* Compute number of CPU cycles to wait for */
counter = (ADC_STAB_DELAY_US * (SystemCoreClock / 1000000));
while(counter != 0)
{
counter--;
}
}
/* Enable the ADC end of conversion interrupt for injected group */
__HAL_ADC_ENABLE_IT(hadc, ADC_IT_JEOC);
/* Enable the ADC overrun interrupt */
__HAL_ADC_ENABLE_IT(hadc, ADC_IT_OVR);
/* Check if Multimode enabled */
if(HAL_IS_BIT_CLR(ADC->CCR, ADC_CCR_MULTI))
{
tmp1 = HAL_IS_BIT_CLR(hadc->Instance->CR2, ADC_CR2_JEXTEN);
tmp2 = HAL_IS_BIT_CLR(hadc->Instance->CR1, ADC_CR1_JAUTO);
if(tmp1 && tmp2)
{
/* Enable the selected ADC software conversion for injected group */
hadc->Instance->CR2 |= ADC_CR2_JSWSTART;
}
}
else
{
tmp1 = HAL_IS_BIT_CLR(hadc->Instance->CR2, ADC_CR2_JEXTEN);
tmp2 = HAL_IS_BIT_CLR(hadc->Instance->CR1, ADC_CR1_JAUTO);
if((hadc->Instance == ADC1) && tmp1 && tmp2) 
{
/* Enable the selected ADC software conversion for injected group */
hadc->Instance->CR2 |= ADC_CR2_JSWSTART;
}
}
/* Process unlocked */
__HAL_UNLOCK(hadc);
/* Return function status */
return HAL_OK;
}