Simple USB - ICOM bus interface, SM7LCB

Last updated 15 June 2009. Back SM7LCB remote page


On my ICOM bus interface page I show a simple interface between a standard COM-port and the ICOM bus made by Bill, G3MCS. But the normal COM-port is today not so common on new computers and you need to get an USB to COM-port adapter to use the simple interface made by Bill. But I will here show a very simple USB to ICOM bus interface which is very easy to build.

This interface use a ready made USB to serial cable from the company FTDI. There main product chips for USB to COM-port and also USB to LTP-port. But they also sell  the TTL-232R cable which easy can be used to build this interface. 



Below is the simple schematic of this interface!

  • The FTDI TTL-232R 5V version can be find at ELFA. Note that it shall be the 5V version (there is a 3.3V also).
  • The red wire support +5V from the USB and is used to pull-up the ICOM-bus.
  • The yellow (TxD) and Orange (RxD) is the serial data from USB with TTL levels (same as for ICOM-bus).
  • The black wire is 0V.
  • The zener diode is a small ESD protecting but not needed.



It is easy to build. I build it in a small box with two BNC connectors for the ICOM bus connection. Maybe you want other connector.

The picture below show the internal wiring.


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