Cinterion
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Java Terminals Hardware Interface Overview
3.6 GPIO Interface
39
EHSxT_BGS5T_HIO_v03
2016-05-26
Confidential / Released
Page 27 of 50
EHS5T‘s RS-485 interface is based on the TIA/EIA-485 standard defining electrical character-
istics of drivers and receivers for use in balanced multidrop communication systems. RS-485
is used in a lot of different fieldbus systems like Profibus, Interbus, Modbus and P-net.
RS-485 uses a shielded twisted pair cable where the inner pairs are used for balanced com-
munication. The two conductors in each pair are called A and B. RS-485 is usually half-duplex.
Data transmission speed depends on the length of the RS-485 bus cable and may be up to
115kbps.
Note:
If employing EHS5T‘s RS-485 interface be sure not to switch off the EHS5 module, e.g.,
by calling AT^SMSO, to put the module into Power Down mode. This completely occupies and
therefore blocks the RS-485 bus, and may thus lead to a higher current consumption.
Also, be sure not to activate SLEEP mode, e.g., by setting AT^SPOW with <mode>=2, for the
EHS5 module, as the module may no longer be able to wake up from SLEEP mode, and will
then have to be reset.
3.6.1
Serial Interface ASC1
With EHS5T and EHS6T Java Terminals two respectively four pins at the GPIO connector can
be configured as ASC1 interface signals to provide a 2- or 4-wire serial modem interface ASC1.
The following pins at the GPIO connector can be configured as ASC1 interface signals: RXD1,
TXD1, RTS1 and CTS1 (see also
). The configuration is done by AT command
AT^SCFG - see
. It is non-volatile and becomes active after a Java Terminal restart.
Java Terminals are designed for use as a DCE. Based on the conventions for DCE-DTE con-
nections they communicate with the customer application (DTE) using the following signals:
•
Port TXD @ application sends data to Java Terminal’s TXD1 signal line
•
Port RXD @ application receives data from the Java Terminal’s RXD1 signal line
Hardware handshake using the RTS1 and CTS1 signals is only supported for EHS6T.
