STM32F103 Dual ADC with DMA skips channel

[Jeroen3]

Posted on November 03, 2016 at 14:38

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[Jeroen3]

Posted on November 03, 2016 at 16:18

Well. What a bit of rubber duck debugging can't fix, heh...

1. The skipped channel was caused since the ADC was written to while  ADC_CR2_CAL was on.

Fix:

  /* Power ON */

  ADC1->CR2 = ADC_CR2_ADON | ADC_CR2_CAL;

  ADC2->CR2 = ADC_CR2_ADON | ADC_CR2_CAL;

  /* Wait 4 ADC cycles, 24 cpu cycles */

  timeout = 24;

  while(timeout--);

  /* Auto Calibrate */

  ADC1->CR2 |= ADC_CR2_CAL;

  ADC2->CR2 |= ADC_CR2_CAL;

  while(ADC1->CR2 & ADC_CR2_CAL);

  while(ADC2->CR2 & ADC_CR2_CAL);

  // Clear all flags

  ADC1->SR = 0;

  ADC2->SR = 0;

2. After this, an address misalignment occurred using the DMA. This was caused by setting ADC_CR2_DMA before turning on the DMA channel. This causes an inevitable DMA operation (with CAL results) when turning the DMA channel on.

So many little things aren't in the manual...

[Tesla DeLorean]

Posted on November 03, 2016 at 16:53

So many little things aren't in the manual...

 

Somehow I suspect a manual that covered all the minutiae of the implementation would be impenetrable, and it is not as if most people read it now anyway..