USB to Serial Port Converters

Nils Kassube kassube at
Sun Feb 28 21:07:45 UTC 2010

Karl F. Larsen wrote:
> 	A year or two ago I bought one of these, with CE  FC as the
> maker of this device. It does not work well at all.

Can you tell us the USB ID so we know which part doesn't work? You can 
find it with the lsusb command while the device is connected compared to 
the output with the device disconnected.

> 	I need one that reliably puts 5 volts from the USB onto the
> proper serial port pin.

There is no pin designated for 5V on a serial port [1], therefore I 
don't think you will find such a thing.

> I also need to use the serial port
> XON/XOF flow control.

XON/XOFF flow control is available with every such part because it works 
over the RX/TX signal lines. It is more a question if the software on 
both ends supports XON/XOFF.

> 	Can anyone give me a clue as to what to buy? My old one
> provides the 5 volts for about 15 seconds and quits.

Do you want to misuse a signal pin as a supply pin for the equipment 
connected to the serial port? Then the device might detect your load as 
a short circuit and shuts down the output. The problem is that the 
available current is very limited on the signal lines. Maybe you should 
consider an external power supply, e.g. directly from another USB port.


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