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ADC operating above max speed?

Question asked by Trip Richert on Jul 18, 2014
Latest reply on Jul 22, 2014 by Robin_Shen

Using a timer, I measured my sample rate of my ADC at ~3Msps.

I am using a k60f120 board, which according to k60P144M120SF3, has a max ADC sampling rate of only ~800ksps.

 

Is it plausible that my ADC is reading that much faster than the rated speed, or am I doing something wrong?

 

I set my ADC to sample continuously and trigger DMA with the DMAEN flag.  I am sampling with 12 bit resolution.  The DMA just reads the ADC1_RA and writes to a buffer.

 

To time, I am using the MQX _time_get_ticks and _time_diff_microseconds by triggering a DMA major loop interrupt after 256 samples.  I measure 85 microseconds for 256 samples ~= 3Msps.  I am running in debug mode, not release mode, but I am not setting breakpoints.

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