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RS-232C Level Converter
Description
The RS-232C Level Converter option connects to a computer through the DB9 connector on the
back of the SWL IR Remote unit. Just plug your computer into the SWL IR Remote and you can
use any software program that can communicate with your receiver. It is possible to use the RS-
232C Level Converter to convert baud rates between your radio and computer. You can use
newer programs on your computer at higher baud rates (9600 or 19200) and radio baud rates of a
different value. This is quite valuable if you want to use newer computer programs to control
older radios. This is a great way to interface an older radio with a newer software program.
Operation
The Level Converter takes in characters from a computer and sends them on to the radio, then
waits for return characters from the radio if the communications gets a response. Most Level
Converters just convert the electrical signals from RS-232C to TTL as required by the radio. The
SWL IR Remote has two serial channels (called a UART). One connects to the radio using TTL
level signals for the radio. The other channel is converted to RS-232C level signals and connects
to a computer. Going through the SWL IR Remote controller permits control over the flow of
traffic to and from the radio. IR commands can be interjected into the time between the computer
commands permitting operation by the computer and the Universal Remote.
Having two independent communications channels allows each channel to communicate at a
different speed (baud rate). ICOM radios respond to all CI-V messages and this then provides a
“pacing” of the commands from the computer. If properly implemented, commands are sent from
the software and the software waits for a response. Because the software waits for a response to
all commands, it should not initiate another command until it gets a response, or enough time has
gone by to be sure a response is not coming. This will synchronize commands to the radio and
the radio will not be overrun.
There is a delay of about one character time when using the Level Converter. This is not enough
of a delay to cause any problems with most computer software. There is a normal turn around
time in the communications and the software, if properly implemented, should handle this delay.
The CI-V interface is a single line, half-duplex mode of communications. The computer sends a
command, and then waits for a response on the same line. Because of the single line of
communications, characters sent to the radio are echoed back to the sender. The Level Converter
mimics this so that software thinks that it is talking directly with a radio, which will echo back all
characters sent.
