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ADC polling of multiple channels

Johannes Hofmann
Associate II

After setting up a 4 channel read with DMA, I ran into the problem, that the value of the internal temperature sensor seemed to not change at all. The values of the read out potentiometer however were plausible.
So I wanted to check all used channels by manually polling them.
But in this case it seems that the EOS flag is set before the loop finishes reading the data, though I have the WAIT bit set in CFGR1.

 if( (this->adcReg->ISR & ADC_ISR_ADRDY) != 0 )
    this->adcReg->CR |= ADC_CR_ADSTART;

 for( uint8_t index = 0; index < this->numOfChannels; index++){
    while( (this->adcReg->ISR & ADC_ISR_EOC) != 1 );
    this->adcData[index] = this->adcReg->DR;

 So here my debugger runs to infinity stuck in the while loop with index = 2 and adcData[0] and [1] having data.

Do you have ideas why this isn't working? I also read in the forum, that multichannel data handling is not recommended for polling, but it must work according to how I understood the timing diagrams in the reference manual.

Thanks for your help in advance.

Senior III

Have you set sequence count to 2 in the ADC initialisation (not the DMA)?

Hi Tobe,
What do you mean with sequence count? Is it inside a register? Because I didn't find anything in the respective register section of the ref manual.

Have you tried searching for a "count" at all? Seems like DMA/ADC is set up for 2 conversions, but you expect 4.

Hey Tobe,
No in this case I don't read with DMA, I poll the 4 channels manually.
I forgot to mention, that the readout with DMA was successful.

But I found a mistake in the code in the meantime here


while( (this->adcReg->ISR & ADC_ISR_EOC) != 1 );


This must be correctly


while( !(this->adcReg->ISR & ADC_ISR_EOC) );