Sunday, September 25, 2011

USB <=> TTL <=> RS232C(Serial, COM)

While I was thinking about homebrewing PC control cables for various TRXs, I became quite confused so I made a schimatic to help me understand the issue.
In today's serial communications, there are three 'states' which are 'USB', 'TTL(UART)' and 'RS232C'. The source of the confusion comes from the fact that each maker employs a different method to hook up their TRXs to a PC.

ICOM's CI-V certainly is a nice idea, but it requires a rather proprietary adapter (CT-17). Kenwood/Yaesu fixed TRXs are more handy as they have a DB9 port so can be hooked up with a generic cable (plus a USB-Serial adapter).

It is known that CI-V and FT-817/857/897 cables are easily homebrewed using a USB-UART conversion IC such as FT232R or even utilizing an old mobile phone cable.

As to the GPS sported VX-8G, direct RS232C level signals apparently come out at the data jack. Yaesu sells CT-143 cable for connecting it with a PC, which perhaps is merely a direct wiring to a DB9 connector, not like the CT-62 level converter cable.

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