A RC filter and an NTC are connected to ADC0 and ADC4 respectively. These analog references can be used as input to the ADC. Both analog references can be disconnected by cutting the cut-straps on the bottom side of the board.
The RC filter (1st order low-pass) has an approximate 3dB cut-off frequency of 160Hz. The input to the RC filter is one of the UC3 GPIO pins that can be configured to output a PWM signal to the RC filter. This can be used to generate a DC voltage on the output of the RC filter, which can be measured on the ADC. As this is a 1st order filter, the ripple on the DC voltage is inversly proportional to the input frequency. A higher input frequency will give lower ripple on the output.