Analog IO

A RC filter, light sensor and a NTC are connected to ADC5, ADC6 and ADC7 respectively. These analog sources can be used as input to the ADC. All of the analog signals can be disconnected by cutting the cut-straps on the bottom side of the board.

The RC filter (1. order low-pass) has an approximate 3dB cut-off frequency of 159 Hz. The input to the RC filter is GPIO5(PD5) on the Atmel ATmega1284P which 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 ADC5 pin. As this is a 1.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.