Question
Anti-alias IIS2DLPC
I am trying to configure the IIS2DLPC for anti-aliasing as indicated by figure 3 section 3.4 of an5201.
I am seeing frequency folding in the spectrum. I am playing a 300 and 500 Hz sine wave alternately on a sound table to vibrate the sensor. Each tone plays for 1.5s then switches frequency.
I had the IIS2DLPC configured for, High Performance, 1600Hz ODR, and Band Width ORD/4 or 400Hz. I was expecting the 500Hz to be strongly attenuated. Is my understanding of how the anti-aliasing filter works, or my setup incorrect?
Here is the config code
status = iis2dlpc_power_mode_set(&iis2dlpcctx, iis2dlpc_mode_t::IIS2DLPC_HIGH_PERFORMANCE); //IIS2DLPC_HIGH_PERFORMANCE_LOW_NOISE);
report(status);
status = iis2dlpc_data_rate_set(&iis2dlpcctx, iis2dlpc_odr_t::IIS2DLPC_XL_ODR_1k6Hz);//iis2dlpc_odr_t::IIS2DLPC_XL_ODR_12Hz5);//iis2dlpc_odr_t::IIS2DLPC_XL_ODR_1k6Hz);
report(status);
status = iis2dlpc_filter_bandwidth_set(&iis2dlpcctx, iis2dlpc_bw_filt_t::IIS2DLPC_ODR_DIV_4);
report(status);
// Set scale 2g/4g/8g/16g
status = iis2dlpc_full_scale_set(&iis2dlpcctx, iis2dlpc_fs_t::IIS2DLPC_8g);
report(status);