Pi Pico & Arduino Nano Function Generator

Using DDS and an R2R resistor ladder the pi pico can generate Analog Signals just like any microcontroller.
In order to get individual GPIO to act as individual binary bits for each value being output to the R2R ladder to make full waves, i had to create a function to convert decimal values in a C array to binary GPIO values.
I have wanted to get my pico to communicate with an atmega for a while so i achieved that using UART.
The arduino through UART tells the pico to increase or decrease the speed of the wave. But the button that changes the waveforms shape is read by the pico. It was just less code to manage by leaving that to the pico.