User:EnthusiasticGeek/Keyboard Case

So far, these are my personal observations of the PinePhone Keyboard. The name of that will change -- oops.

This Keyboard Case is a case for the PinePhone and PinePhone Pro. As the name implies, it adds a keyboard to the phones. It also has a 6000 mAh battery that essentially tripples the phone's 3000 mAh battery life.

Connectivity

The Keyboard Case has six pins that connect it to the PinePhone or PinePhone Pro.

INT  SDA  SCL
VBUS VBAT GND

The SDA and SCL pins belong to the I2C Bus.

VBUS connects to the USB +5V line. See Charging Information for more information

The VBAT pin connects to the battery. This powers the keyboard if it is out of power.

INT is a pin that's used for interrupts. In this case, it is used so the phone can request key presses from the keyboard..

Charging Information

In most schematics, including the PinePhone and PinePhone Pro, the usually +5V coming from the usb connector is named VBUS. This voltage is fed into the System-On-a-Chip in the PinePhone (Allwinner A64) or PinePhone Pro (RK3399S). The SOC then manages this voltage and charges the battery.

The VBUS rail is also accessed through one of the pogo pins on the back of the phone. This is what the keyboard uses to charge the phone. The output of the IP5209 chip is connected to the VBUS rail through this pogo pin, which charges the phone. This makes the keyboard act as a USB charger with only +5V and GND connected, which charges the phone.

This breaks the USB-C spec, as even if the phone and connected device negotiates that ths phone shall be the sink, +5V will still be put out by the PinePhone or PinePhone Pro. This means that a charger plugged into the phone while the keyboard is connected may result in some unintended behaviors.

This also means that, although the phone is connected