stm32f207 DMA+ADC , captures only one channel only once

From RM003 page 224

...

10.8.1 Using the DMA

Since converted regular channel values are stored into a unique data register, it is useful to

use DMA for conversion of more than one regular channel. This avoids the loss of the data

already stored in the ADC_DR register.

When the DMA mode is enabled (DMA bit set to 1 in the ADC_CR2 register), after each

conversion of a regular channel, a DMA request is generated. This allows the transfer of the

converted data from the ADC_DR register to the destination location selected by the

software.

Despite this, if data are lost (overrun), the OVR bit in the ADC_SR register is set and an

interrupt is generated (if the OVRIE enable bit is set). DMA transfers are then disabled and

DMA requests are no longer accepted. In this case, if a DMA request is made, the regular

conversion in progress is aborted and further regular triggers are ignored. It is then

necessary to clear the OVR flag and the DMAEN bit in the used DMA stream, and to reinitialize

both the DMA and the ADC to have the wanted converted channel data transferred

to the right memory location. Only then can the conversion be resumed and the data

transfer, enabled again. Injected channel conversions are not impacted by overrun errors.

When OVR = 1 in DMA mode, the DMA requests are blocked after the last valid data have

been transferred, which means that all the data transferred to the RAM can be considered

as valid.

At the end of the last DMA transfer (number of transfers configured in the DMA controller’s

DMA_SxNDTR register):

• No new DMA request is issued to the DMA controller if the DDS bit is cleared to 0 in the

ADC_CR2 register (this avoids generating an overrun error). However the DMA bit is

not cleared by hardware. It must be written to 0, then to 1 to start a new transfer.

• Requests can continue to be generated if the DDS bit is set to 1. This allows

configuring the DMA in double-buffer circular mode.

To recover the ADC from OVR state when the DMA is used, follow the steps below:

1. Reinitialize the DMA (adjust destination address and NDTR counter)

2. Clear the ADC OVR bit in ADC_SR register

3. Trigger the ADC to start the conversion.

 ...

I am debugging that ADC1->CR2.DDS register but it appears to be set to 0 the whole time

> DMA would need to be in circular mode, so it restarts after TC

it already is

>Avoid blocking code in the interrupt. Toggle a GPIO, it is far less invasive and time consuming, especially with short buffers.

the error was there before i placed the uart print code, but i took it out again just in case.

>Check none of the call-back code stops the DMA/ADC

So far all callbacks are default generated by cubeMX, ill check

im trying different triggers ,even continuous mode (triggerless)

NVIC interrupts for the triggers are not enabled in any of my tests.

So note taken but it must be something else

• ADC_DMAError() is never reached

• following void HAL_DMA_IRQHandler(DMA_HandleTypeDef *hdma)

...

       /* Disable the half transfer interrupt if the DMA mode is not CIRCULAR */

       if((hdma->Instance->CR & DMA_SxCR_CIRC) == RESET)

       {

         /* Disable the half transfer interrupt */

         hdma->Instance->CR &= ~(DMA_IT_HT);//this code is reached but my DMA mode IS CIRCULAR

       }

....

... ...

     /* Disable the transfer complete interrupt if the DMA mode is not CIRCULAR */

     else

     {

       if((hdma->Instance->CR & DMA_SxCR_CIRC) == RESET)

       {

         /* Disable the transfer complete interrupt */

         hdma->Instance->CR &= ~(DMA_IT_TC);//this code is also reached but my DMA mode IS CIRCULAR

.....

• inside void HAL_ADC_MspInit(ADC_HandleTypeDef* hadc)

/* ADC1 DMA Init */
 /* ADC1 Init */
 hdma_adc1.Instance = DMA2_Stream0;
 hdma_adc1.Init.Channel = DMA_CHANNEL_0;
 hdma_adc1.Init.Direction = DMA_PERIPH_TO_MEMORY;
 hdma_adc1.Init.PeriphInc = DMA_PINC_DISABLE;
 hdma_adc1.Init.MemInc = DMA_MINC_ENABLE;
 hdma_adc1.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD;
 hdma_adc1.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;
 hdma_adc1.Init.Mode = DMA_CIRCULAR;//<----------------------------------------------------:D
 hdma_adc1.Init.Priority = DMA_PRIORITY_LOW;
 hdma_adc1.Init.FIFOMode = DMA_FIFOMODE_DISABLE;

• Inside HAL_DMA_Init

/* Write to DMA Stream CR register */
 hdma->Instance->CR = tmp;// <---- hdma->Instance->CR doesnt get tmp value for some reason, it remains 0

 I cannot change the value manually in the Debugger Expressions window.......

Something is preventing this memory to being written, something is preventing the init code to write the configurations in the DMA2 Stream0 registers.That memory addr 0x40026410 happens to be where DMA2 Stream 0 peripheral is mapped, as expected in my cubeMX configuration.

I just opened a question about this https://community.st.com/s/question/0D53W00001B0menSAB/why-cant-i-write-into-mem-0x40026410