ADC in STM32F415ZG, how can i reached the Conversion time in the Datasheet ?

[Ed Raab]

Posted on June 27, 2018 at 11:24

hallo,

i am trying to program the ADC in the STM32F415ZG. I use the hal library and have written interface functions and modifications to adapted it to my application. I have tried out the dma and the Interrupt driven adc conversion via SW-Trigger starts in a loop with other procedures. The shortes ADC conversion time of a single value measured to approximately 6 Mikroseconds. I used an ADC clock of 24MHz. According to the data sheet there are Conversion times below 0,5 Mikroseconds reachable. Is there anybody who have a code example for this.

Thanks.

best regards

Ed

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[AvaTar]

Posted on June 27, 2018 at 12:50

By reducing the resolution to 6 bit, for instance.

The reference manual says:

The minimum conversion time for each resolution is then as follows:

• 12 bits: 3 + 12 = 15 ADCCLK cycles

• 10 bits: 3 + 10 = 13 ADCCLK cycles

• 8 bits: 3 + 8 = 11 ADCCLK cycles

• 6 bits: 3 + 6 = 9 ADCCLK cycles

[Ed Raab]

Posted on June 27, 2018 at 16:30

hallo,

i have read this. But with 12Bits resolution with 15 ADCCLK cycles and 24MHz the conversion time is 0,625 mikroseconds. I measure more than 6 mikroseconds. There is a big difference??

best regards

Ed

[AvaTar]

Posted on June 27, 2018 at 16:43

What exactly do you mean with 'conversion time' ?

The quote from the reference manual refers to the conversion alone.

For an ADC value, you have sampling time + conversion time.