STM32L0 ADC with External Trigger and DMA

[EHarr.1]

Hello,

I am having a bit of a problem with using the ADC on the STM32L072 in combination with the External Trigger and the DMA.

I have just two conversions set not continuous mode and not discontinuous, but the DMA is set to take 32 results.

If I trigger by software, then it neatly converts the two channels and put the results in the buffer. When it hits the End of Sequence ISR the START bit is clear.

If I trigger the ADC start from the timer it keeps going with the conversions, filling the buffer and in the End of Sequence interrupt the START bit is still set.

Faulty setup:

ADC                

  ISR       0x00000000   

  IER       0x00000008   

    ADRDYIE   0       

    EOSMPIE   0       

    EOCIE    0       

    EOSIE    1       

    OVRIE    0       

    AWDIE    0       

    EOCALIE   0       

  CR       0x10000001   

    ADEN    1       

    ADDIS    0       

    ADSTART   0       

    ADSTP    0       

    ADVREGEN  1       

    ADCAL    0       

  CFGR1      0x00000881   

    AWDCH    0x00      

    AWDEN    0       

    AWDSGL   0       

    DISCEN   0       

    AUTOFF   0       

    AUTDLY   0       

    CONT    0       

    OVRMOD   0       

    EXTEN    0x2      

    EXTSEL   0x2      

    ALIGN    0       

    RES     0x0      

    SCANDIR   0       

    DMACFG   0       

    DMAEN    1       

  CFGR2      0x80000000   

    OVSE    0       

    OVSR    0x0      

    OVSS    0x0      

    TOVS    0       

    CKMODE   0x2      

  SMPR      0x00000005   

    SMPR    0x5      

  TR       0x0fff0000   

    HT     0xfff     

    LT     0x000     

  CHSELR     0x00000003   

    CHSEL18   0       

    CHSEL17   0       

    CHSEL16   0       

    CHSEL15   0       

    CHSEL14   0       

    CHSEL13   0       

    CHSEL12   0       

    CHSEL11   0       

    CHSEL10   0       

    CHSEL9   0       

    CHSEL8   0       

    CHSEL7   0       

    CHSEL6   0       

    CHSEL5   0       

    CHSEL4   0       

    CHSEL3   0       

    CHSEL2   0       

    CHSEL1   1       

    CHSEL0   1       

  DR       0x00000041   

  CALFACT     0x00000041   

  CCR       0x00c00000   

    PRESC    0x0      

    VREFEN   1       

    TSEN    1       

    LFMEN    0       

DMA1                

  ISR       0x00000000   

  CCR1      0x000025a1   

    MEM2MEM   0       

    PL     0x2      

    MSIZE    0x1      

    PSIZE    0x1      

    MINC    1       

    PINC    0       

    CIRC    1       

    DIR     0       

    TEIE    0       

    HTIE    0       

    TCIE    0       

    EN     1       

  CNDTR1     0x00000020   

  CPAR1      0x40012440   

  CMAR1      0x200007a0   

If I just clear the EXTEN and EXTSEL in ADC1.CFGR1, then it behaves as I extpect.

Any suggestions why the timer keeps triggering conversions even though it shouldn't?

Cheers,

Ed.

[waclawek.jan]

> Any suggestions why the timer keeps triggering conversions even though it shouldn't?

Why it shouldn't? Is it set to one-pulse mode?

JW

[EHarr.1]

The timer is free running and is synchronised to an external clock.

I only want it to trigger the ADC once. In the setup above both DISCEN and CONT are set to zero so I would expect the ADC to disable itself (clear the START bit) at the end of the conversion sequence.

Cheers,

Ed.

[EHarr.1]

From the current data sheet (DocID025941 Rev 5):

"When hardware trigger is selected in single mode (CONT=0 and EXTEN = 01), ADSTART is not cleared by hardware when the EOS flag is set. This avoids the need for software having to set the ADSTART bit again and ensures the next trigger event is not missed."

Which implies that if CONT = 0 and EXTEN = 10 then the ADSTART will be cleared when EOC flag is set.

Ed.