ADC 1 channel with circular DMA of 16 bytes: array [0] stay at '0'

[lclor]

Hello,

I have an issue and until now didn't find the solution :

Using ADC2, one channel IN12, triggered by timer every 100µs, using circular DMA sized of 16 half-words, the array [0] value is always 0, the array's index used by DMA is from 1 to 16, not 0 to 15. See below screen shots :

 

code : 

volatile uint16_t _v_Adc2Values [18]; // Define to 18 to see the shift

HAL_ADC_Start_DMA (&hadc2, (uint32_t *) _v_Adc2Values, 16);
HAL_TIM_Base_Start_IT (&htim15);

result :

When I starts my software this morning to make the screen shots, the 1st start, I have not the issue, the values comes from 0 to 15 in array. Then I restarted my software several times, and all these tries the array result was shifted like the screen shot.

Thank for your help.

Best regards,

Laurent

[Ozone]

I think the DMA settings are missing in your description.

> Then I restarted my software several times, and all these tries the array result was shifted like the screen shot.

Does "restart" mean a reset without power cycle ?
Perhaps you inadvertendly change the DMA settings somewhere.
I would check and compare the relevant DMA register contents for both cases, i.e. before and after a restart.

[lclor]

yes restart is without power cycle.

I do again the same test : power off, power on, launch in debug and run, and this time, the array is shifted.

[Ozone]

> ... the array is shifted.

Not exactly. The values have shifted within the array.

Which indicates the DMA target address has changed.

[lclor]

I would like to say that values are written by DMA in array from index 1 to 16 instead of 0 to 15.