Nominal Animal
Senior Member

I agree: taylor(1073741824) returns = -2147483522. When lines 84-88 of https://github.com/PaulStoffregen/Audio/synth_sine.cpp are changed to if (ph >= 0xC0000000 || ph < 0x40000000) { //...

KD5RXT's suggestion is what came to my mind first as well. Other options do exist. One is to use a dual supply voltage level shifter IC like TI TXU0202 (UART RX+TX), TXU0204 (UART RX+TX+CTS+RTS), or TXU0304 (SPI),...