He also added a low-pass filter and a comparator to clean up the signal into a nice square wave, which was fed into the Arduino to parse the Differential Manchester-encoded data.

With a handful of low-leakage passive components and two high-impedance op amps, you can build a sine/square-wave generator with output period of a minute and more.

With DIV_SEL_1 tied low and DIV_SEL_2 tied high, the 100:1 divider is selected. The MSFS5 is a pin-selectable, seventh-order, low-pass/six-pole bandpass switched-capacitor filter.