Figure 44: External RTC Reference Schematic
2.14.3 Unused I
2
C Signal Termination
All unused I
2
C can be left unconnected if the according I
2
C port is switched off in software.
Otherwise, it is recommended to keep the pull-up resistors available. Unused I
2
C signals can be
configured to be GPIO.
2.15 UART
The Apalis module form factor features up to four UART interfaces. Even though, the UART1 is
specified as a full-featured UART. Some modules might not provide all the control signals. Please
read the relevant datasheet of the modules carefully. The UART1 is the standard console output
interface for the Linux and Windows Embedded Compact operating system. It is desirable to keep
at least the RX and TX signals of this port accessible for system debugging.
UART2 features RTS and CTS signals for hardware flow control while UART3 and UART4 do not
feature any flow control signals. Some modules might provide additional flow control signals on
non-standard pins.
2.15.1 UART Signals
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