SNLS757B June 2024 – November 2024 TUSB2E221
PRODMIX
In I2C mode GPIO0 defaults as an enable control for Carkit UART mode. GPIO0 is an active low signal to enable Carkit UART mode. GPIO0 can be controlled through APU or SoC. When APU or SoC is not powered on or the firmware has not been loaded, GPIO0 is low. When GPIO0 is low, the UART mode allows access to the APU or SoC debug interface through the USB port.
Default Carkit UART direction is DP → eDP (RX) and eDN → DN (TX).
On the rising edge of GPIO0, followed by TMODE_SWITCH, the TUSB2E221 is enabled and enters the default state, ready to accept eUSB2 port reset, configuration or RAP. The repeater mode is configured as host or peripheral depending on the eUSB2-defined configuration received from eUSBr and acknowledged by the repeater.
UART mode enable is controlled through GPIO0 after power up. This can be changed through UART_use_bit1_Px bit in UART-PORTx register, so UART mode enable can be controlled through a register instead of GPIO0.