Murata Electronics Corporation 27 6/2/2021
6. WIT2420 DEVELOPER’S KIT
The WIT2420 Developer’s Kit contains two self-contained wireless modems (HN-510s) built
around the WIT2420M OEM module. In addition, two WIT2420M OEM modules are
included in the kit. The self-contained units allow developers to get up and running quickly
using standard RS-232 interfaces without having to build a CMOS level serial interface. In
addition, the self-contained modems include status LEDs to provide modem status
information visually. The built-in battery pack allows the developer to use the modems
without being tethered to a power source. This provides a simple way to test the range of the
radios. Other than the true RS-232 signals of the serial interface, the self-contained modems
operate exactly as the OEM modules.
Connection is made to the HN-510s through a standard DB-9 connector. The HN-510s are
set up as DCE devices requiring the use of a straight-through cable to connect to DTE
devices. The pinout is provided in Section 7.3. The modems can be used with just a three
wire connection. Transmit data, receive data and ground are the three required connections.
Note that in this configuration, no flow control is available as the WIT2420 does not support
software flow control.
When the developer’s kit is shipped from the factory, one HN-510 is set up as a base station
and the other is set up as a remote. The interface rate for both modems is set at 9600 bps.
The default setting for the network key allows the modems to communicate without changing
any settings. As a quick test, separate the two modems by about 5 feet, plug in the power and
turn the modems on. Do not connect the modems to any device. The Carrier Detect (CD)
LED on the base station will come on immediately. After a few seconds, the CD LED on the
remote will come on. This indicates that the modems have synchronized and have
established a communications link.
An important point to remember is that if the base station is in Sleep mode, no
communications can take place until (1) the base station is taken out of sleep mode and (2)
the remote has synchronized with the base station. As the Sleep signal is brought out on the
pin usually occupied by DTR, connecting the base station to a PC serial port with DTR de-
asserted will put the modem into sleep mode. Some communications programs will attempt
to communicate immediately after asserting DTR. The base station will transmit this data,
but the remote will not be synchronized with the base station and will not receive the
transmission. In this instance, do not connect the Sleep signal to DTR of the serial port.
6.1. COM24/WinCOM24
Provided with the developer’s kit are two simple communications programs designed
especially for the WIT2420.
COM24. This program provides a simple command interface to the modems along with
function key control for manipulating the serial port control lines and baud rates. This
program is designed to run under DOS.
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