+ #if CPU_AVR_ATMEGA8 || CPU_AVR_ATMEGA328P || CPU_AVR_ATMEGA168
+ ADMUX &= ~(BV(MUX3) | BV(MUX2) | BV(MUX1) | BV(MUX0));
+ #elif CPU_AVR_ATMEGA32 || CPU_AVR_ATMEGA64 || CPU_AVR_ATMEGA128 || CPU_AVR_ATMEGA1281
+ ADMUX &= ~(BV(MUX4) | BV(MUX3) | BV(MUX2) | BV(MUX1) | BV(MUX0));
+ #else
+ #error Unknown CPU
+ #endif