Example Description

This example describes how to use sleep uart api.

Requirement Components:
    a USB to TTL Adapter

Pin name PA_18 and PA_23 map to GPIOA_18 and GPIOA_23:
 - PA_18 as UART0_RX connect to TX of USB to TTL adapter.
 - PA_23 as UART0_TX connect to RX of USB to TTL adapter.
 - GND connect to GND of USB to TTL adapter.

Open the Trace Tool and set baud rate to 115200,Data Bits 8, no parity,  1 stop bit for mbed device
Open the Trace Tool and set baud rate to 38400, Data Bits 8, no parity,  1 stop bit for Usb to TTL Adapter.

Boot up device, and wait around 5 seconds, device will enter sleep mode.
Then you can press the Enter key or type characters to wakeup system and the characters will be shown in the Trace Tool for Usb to TTL Adapter.

Note: user need to ENABLE the LOW_POWER_RX_ENABLE in array uart_config[] in rtl8710b_intfcfg.c to enable uart low power rx function
      and ON the wakeup event "BIT_SYSON_WEVT_UART0_MSK" in array sleep_wevent_config[] in rtl8710b_sleepcfg.c to enable uart wakeup event before make.