USARTS

USART0 of the UC3A is connected to the USART1 of the UC3B in order to form a USART to USB bridge. This bridge can be used by a host (PC) to communicate with the UC3A over USB.

The header J11 can be used to either interface the signals from UC3A or UC3B for custom purposes. This implies that the default firmware must be changed in order to set one of the communication sides into inactive mode (configure the pins as GPIO inputs).

The channel 0 of the ABDAC is multiplexed with the USART0 lines RTC and CTS of the UC3A/UC3B with jumpers. The default configuration is set up for the USART and connects the signal lines to the UC3B device. This is indicated in the image below. In order to use the signal lines with the ABDAC instead set the jumpers as described in the AUDIO.



Pinout

Pin on header UC3A GPIO Name UC3A function UC3B GPIO Name UC3B function
1 -- VCC3V3 -- VCC3V3
2 PA3 RTS PA9 CTS
3 PA4 CTS PA10 RTS
4 PA0 RX PA23 TX
5 PA1 TX PA24 RX
6 -- GND -- GND