Table of Contents
Advertisement
RS232 interface for GT47 embedded apps UART
2.2 3-Wire RS232
In the 3-wire configuration, surface mount strap resistors (ST1 and ST2)
are not mounted. Flow control should be disabled on each communicating
device (AT+ IFC)
As the GT47 general purpose outputs each require a resistor pull-up,
these are provided on the RS232 interface PCB. The internal pull-up on
ST1 makes the CTS signal on the DB9 appear as 'inactive' state. As long
as flow control is disabled at the DTE this will not cause a problem. If flow
control cannot be disabled at the DTE, the 'inactive' state on CTS will
prevent the DTE from communicating. In this case, either solder a single
strap resistor between the pads of both ST1 and ST2 as shown in
or enable flow control from the GT47 and add straps ST1 and ST2 (see
section 2.3).
2.3 5-Wire RS232
In the 5-wire configuration, surface mount strap resistors (ST1 and ST2)
must be mounted. This requires soldering 0603-size zero ohm resistors
into positions ST1 and ST2 as indicated in figure 3.
Adding the surface mount resistors should be performed by a skilled
technician and the PCB must first be disconnected from all communicating
devices.
2.4 DCE to DCE (Null-Modem)
If the GT47 UART is to be used as a DTE, instead of the default DCE
configuration, the following changes will be necessary.
gender-changer should be used to convert the output from a socket to a
plug. The following DB9 pin connections should be swapped
The pin-swapping can be achieved by using a "Null-Modem" cable
between the DB9 plugs of the communication devices.
LZT 123 7698 R1B
•
Pin-2 swapped with pin-3
•
Pin-7 swapped with pin-8.
Figure 4
A 9-way DB9
7
Advertisement
Table of Contents
