Function sdm_channel_set_pulse_density 

pub unsafe extern "C" fn sdm_channel_set_pulse_density(
    chan: *mut sdm_channel_t,
    density: i8,
) -> i32

@brief Set the pulse density of the PDM output signal.

@note The raw output signal requires a low-pass filter to restore it into analog voltage, the restored analog output voltage could be Vout = VDD_IO / 256 * density + VDD_IO / 2 @note This function is allowed to run within ISR context @note This function will be placed into IRAM if CONFIG_SDM_CTRL_FUNC_IN_IRAM is on, so that it’s allowed to be executed when Cache is disabled

@param[in] chan SDM channel created by sdm_new_channel @param[in] density Quantized pulse density of the PDM output signal, ranges from -128 to 127. But the range of [-90, 90] can provide a better randomness. @return - ESP_OK: Set pulse density successfully - ESP_ERR_INVALID_ARG: Set pulse density failed because of invalid argument - ESP_FAIL: Set pulse density failed because of other error