2 UART Usage Overview

The EVM boards of Jacinto 7 series processors all have multiple serial ports, which can be seen from Table 2-1. Normally, during hardware design, at least three serial ports are reserved for log information debugging, and the remaining serial ports can be used for communication with external devices. By default, the software parameters of all serial ports are the same, the baud rate is 115200 bit/s, the start bit is 0, there are 8 data bits, the parity bit is None, and the stop bit is 1.

WKUP_UART0 is reserved for DSMC debugging, which is common when the system accidentally triggers the firewall. For SBL boot, MCU_UART0 is used for the serial port output of MCU1_0. For UART boot, MCU_UART0 is used to print the "C" character to determine whether the processor is working normally and to debug whether the HS key burning is successful. The A72 cores log in DRA821 is printed to MAIN_UARTx. The log of all the cores in TDA4X is printed into MAIN_UARTx, except the MCU1_0 log is printed in to MCU_UART0 in the SBL boot.

Therefore, when designing the board, at least WKUP_UART0, MCU_UART0 and one MAIN_UARTx should be reserved. Moreover, they are suggested to have the same Pin configuration with TI reference design. Especially for MCU_UART0, if the Pin is changed then it cannot use “C” character printing to debug in the early stages of project development, because this feature is implemented in the ROM code with the default Pin setting.

When connecting to external devices, it is required to connect the flow control. It is always recommended to connect hardware flow control lines for UART communication. Also, software should enable hardware flow control explicitly. Otherwise, there will be data loss and data corruption.