SioFus

Simple Input Output From USB to Serial adapter is a short code designed to read and write digital signals to/from the real world. Based on the highlighted PINs of the following list, we will be able to setup 4 digital inputs and 2 digital outputs just using a cheap USB2Serial adapter

USB PIN #	Name
1	USB VCC
2	Data -
3	Data +
4	Ground -

Serial (DB9) PIN #	Name
1	DCD (Carrier Detect)
2	RxD (Receive Data)
3	TxD (Transmit Data)
4	DTR (Data Terminal Ready)
5	SG (Signal Ground)
6	DSR (Data Set Ready)
7	RTS (Request To Send)
8	CTS (Clear To Send)
9	RI (Ring Indicator)

Launch the process

./siofus -p /dev/ttyUSB0

Usage as OUTPUT

We will be able to control DTR and RTS PINS on our adapter. The process will be listening (NONBLOCK) for input on the stdin:

• if key "a" is pressed send +5V to PIN4 (DTR)
• if key "s" is pressed send -5V to PIN4 (DTR)
• if key "d" is pressed send +5V to PIN7 (RTS)
• if key "f" is pressed send -5V to PIN7 (RTS)

You would get a current around 0.05A

Usage as INPUT

The idea is being able to tell weather a circuit is open or closed. For this purpouse, we will be using USB PIN 1 as the VCC source. The process will be able to tell when the circuit is closed or opened. These are then PINS used in the Serial conector:

• PIN1 (DCD) : INPUT0
• PIN6 (DSR) : INPUT1
• PIN8 (CTS) : INPUT2
• PIN9 (RNG) : INPUT3

The process will be able to tell to the stdout when a PIN has been closed or opened. For example, when someone connect USB PIN1 to Serail PIN6 (DSR), SioFus will simple write to stdout "#C1#"; when the connection is released, it will write "#O1#".

Compile

gcc -o siofus siofus.c

Version

0.0.1