2: Functional Description
xPico® Embedded Device Server Integration Guide
23
Figure 2-7 Ethernet Connection Example (xPico wired unit only)
Serial Interface
The xPico and xPico Wi-Fi embedded device servers have two external serial interfaces.
The signal levels on the serial interface are 3.3V logic level with 5V tolerant inputs. The
serial interfaces require an external transceiver in order to connect to external RS232,
RS485, or RS422 networks. The signals of Serial Port 1 may be connected as shown in
the reference schematic,
Figure 2-8
serial port example, below. The transceiver shown
in the reference schematic is of type Exar, part number SP336. This transceiver is a
multiprotocol RS232, RS485, RS422 transceiver. Single protocol transceivers may be
used as required. The xPico interface may
also be directly connected to the UART
interface of an external CPU. Serial Port 2 is a three wire interface only. It operates like
Serial Port 1, except it does not support hardware Flow Control (i.e. no RTS/CTS) and
modem control (i.e. no DTR/DCD). It is highly recommended to connect RTS and CTS
for serial port 1.
Table 2-8 xPico and xPico Wi-Fi Serial Port Signals
Signal
Pin
Description
Reset State
TXD1
10
Serial Transmit Data output
Output
RTS1
5
Serial Ready-to-Send / Serial Transmit enable
Output
RXD1
7
Serial Receive Data input
Input
CTS1
16
Serial Clear-to-Send
Input
TXD2
25
Serial Transmit Data output 2
Output
RXD2
23
Serial Receive Data input 2
Input