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Hi, I'm trying to sampling a sinusoidal wave with frequency of 60Khz, put the ADC tooks about 7us to do one conversion. (using fadc = 24Mhz, continuos mode and only one channel enabled).
My question is: What's the minimum time between samples on ADC of STR912F?
you'll have to check the data sheet (maybe on ST's site?) but if I am currect in my calculation, a sample (hence: the conversion + a delay between samples) must not be longer than 8.33 us, otherwise you will be subjected to aliasing.
8.33us / sample is the Nyquist limit, i.e. 120kHz sampling rate for a 60kHz input signal.
But that is the limit for measuring the amplitude and frequency of the input, i.e. to be able to recreate a 60kHz sinus signal with the same amplitude and phase. It will not be enough if you need to measure the waveform of a 60kHz signal (which implies that the signal is formed out of higher-frequency components).
I'm thinking to use ADC DMA to transfer the data faster to an int array. Will this reduce the time below 7us/8,33us?
Without reading your datasheet, I would guess that the answer is no.
The advantage of DMA is normally just a lower the CPU load. In this case, I'm pretty sure that the limiting factor is the ADC - the number of clock cycles/conversion when run in continuous mode.