The Apple MacBook (Early 2015) and Apple 29W USB-C Power Adapter were one of the first products into the market supporting USB Power Delivery over the new USB Type-C interface. Ever wanted to know how the Apple MacBook (Early 2015) communicates to the Apple 29W USB-C Power Adapter?
To see what's going on we use software from Granite River Labs to capture the USB Power Delivery Protocol transactions.
The Apple 29W USB-C Power Adapter supports 12 watts (5 volts @ 2.4 amps) and 29.6 watts (14.8 volts @ 2 amps).
The Apple MacBook (Early 2015) requests 29.6 watts (14.8 volts @ 2 amps) to be provided by the charger.
Eventually, we see that the Apple MacBook (Early 2015) charges at 14.8 watts (14.8 volts @ 1 amps) when the MacBook's charge level is at 80%.