Adil Malik made a low cost FFT LCR meter with an STM32 MCU:
The approach I took was a mixed signal one where a capable analog front end would be paired up with a beefy DSP processor to compute the Impedance. Most importantly, in this scheme, the DSP is responsible for discriminating the phase between the sampled voltage and current waveforms; this approach is preferred because it leads to good accuracy and calibration stability.
See the full post on his blog.
from Dangerous Prototypes https://ift.tt/2N8Sq7t