BeagleBone RS232 Cape
System Reference Manual
Revision A
Page 18 of 22
5.3
UART
There are four UART ports available on the expansion header of BeagleBone; each of
these ports can be used by the RS232 Cape. The TXD and RXD signals of
SN65C322EPW can be connected to the corresponding signals of UART1, 2, 4, and 5 by
installing jumpers for that signal. The default connection is UART2. This UART port is
also supported by software. If user wishes to use a different UART port, the TX and RX
jumpers for that port are required to be installed. User will also need to rebuild the kernel
to support that UART port in software.
A buffer is used to ensure the UART signals do not conflict with BeagleBone’s booting
process. Figure 4 shows the UART selection circuit on the RS232 Cape.
Figure 4. BeagleBone RS232 Cape UART Selection
5.4
UART to RS232
The BeagleBone RS232 Cape features an SN65C322EPW to translate data from RS232
level to UART level. SN65C322EPW is a single-channel line driver and receiver that can
operate from 3.3V to 5V. RX signal of RS232 interface from the D-Sub 9 serial
