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FIBOCOM NL668-EAU-MiniPCIe-10 Hardware User Manual
Page 28 of 56
Pin Name
I/O
Pin Num
Description
UART_TXD
O
31
Module transmits data
UART_RXD
I
23
Module receives data
Table 3-12 Main Serial Port
The following table describes the debug serial port pin:
Pin Name
I/O
Pin Num
Description
DBG_UART_RX
I
28
Module receives data
DBG_UART_TX
O
46
Module transmits data
Table 3-13 Debug Serial Port
3.6.2 UART Interface Application
The serial interface level of MiniPCIe module is 1.8V. If the level of the client host system is 3.3V or other,
a level shifter shall be added to the serial interface connection between the module and the host. The
following figure shows the reference circuit design using level shifter chip.
Figure 3-10 UART Signal Connection 1
Another level shift circuit is shown below. The input and output circuit design in the following dashed part
can refer to that in the solid line part, but pay attention to the connection direction.
