The standard connection for UPDI programming is a 100-mil 6-pin 2x3 header. Even though three pins are sufficient for programming most AVR devices, it is recommended to use a 2x3 header since most programming tools are delivered with 100-mil 6-pin 2x3 connectors.
The following figure shows the recommendation for connecting a UPDI connector to the device.
Figure 1. Recommended UPDI Programming
Circuit Schematic
The decoupling capacitor between VDD and GND must be placed as close to the pin pair as possible. The decoupling capacitor must be included even if the UPDI connector is not included in the circuit.