F446RE ADC with DMA for 1000 samples. (a hack for now, need to get ADC channel from pin name, for asynch operation would need callback)
For 1000 samples with loop adc.read_u16(), sample rate is 2.2us/sample
For DMA, 0.34us/sample.
This matches expected rate: ADC clock at 45MHz, ADC configured for 3CYCLES/sample, cycles = 12+3, rate = 15/45 =0.33us/sample