5.3 How to connect two 3-wire RS232 serial port
In this section is shown how to use the UART1 and UART2 as 3-wire RS232 serial ports.
In the following table are shown the UART1 and UART2 pins numbering.
Number
Name
Primary Function
Description
GPIO
Capable
Voltage
112
UART2_TXD
UART2 TXD signal
Y
+3,3V
113
UART2_RXD
UART2 RXD signal
Y
+3,3V
116
UART1_TXD *
UART1 TXD signal
Y
+3,3V
117
UART1_RXD *
UART1 RXD signal
Y
+3,3V
Table 9
The signal on the module's UART pins are 3.3V logic level, this can not be connected directly to a RS232 device like a PC Serial port,
the use of a transceivers on the base board is mandatory in order to avoid module damage.
Figure 3
In this example an ADM3202ARN IC from Analog Device is used like transceiver for both UART without any control signal. In case RTS
and CTS are need, a transceiver must be used for this signals.
When Linux is installed on a module, UART1 is used like console. The default communications settings is shown in the table below.
Linux console default settings
Baud rate
115200
Data length
8 bit
Parity
none
Stop
1bit
Table 10
*
Note
:
the UART1 is used as Linux Console
D N :
2 3
