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Author Topic: Changing 9 Pin Serial to USB Connection  (Read 573 times)


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Changing 9 Pin Serial to USB Connection
« on: June 29, 2018, 11:12:48 PM »

How would I change a 9 Pin Serial to a USB Connection?

I have a USB-TTL adapter, so it's just a matter of knowing which wire to connect where.

I've chopped off the end and exposed black, red, green and yellow cables.

The USB-TTL adapter has pins labelled GND CTS UCC TXD RXD DTR.

Brian H

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Re: Changing 9 Pin Serial to USB Connection
« Reply #1 on: June 29, 2018, 11:51:16 PM »

You are talking about a standard RS232 Serial connection and not a TTL level serial connection in lets say an Arduino board?
Serial signals are RS232. They swing between a + and - voltage. Between +/- 3 to +/- 25 volts.
TTL is a logic level. +5 and 0 volts. Some newer controllers are 3.3 volts and 0 volts.
So  you can not connect the serial cable to a TTL signal from the board and have it work.

The color of the wires in the cable may have to be rung out with a meter. Not all manufactures use the same color wire for a signal in the cable.

The adapter you are asking about also does not have an RI {Ring Indicate} signal on it. The protocol paper I linked to in your other post. Used the RI signal.

They make USB Serial port adapters. Maybe that would be a better option.
« Last Edit: June 30, 2018, 01:46:38 AM by Brian H »
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