Compared to existing ATmega324 variants, the following enhancements or additional features are available in ATmega324PB:
PTC - Peripheral Touch Controller
CFD - Clock Failure Detection mechanism
OCM1C2 - Output Compare Modulator
USART start frame detection is available in all sleep modes
Analog Comparator output is available on a pin. This pin is multiplexed with PC5
Unique device ID to identify the device
Additional SPI
Additional TWI
Additional Timer/Counters