The tty0tty directory tree is divided in:
module - linux kernel module null-modem
pts - null-modem using ptys (without handshake lines)
When run connect two pseudo-ttys and show the connection names:
(/dev/pts/1) <=> (/dev/pts/2)
the connection is:
TX -> RX
RX <- TX
The module is tested in kernel 3.10.2 (debian)
When loaded, create 24*2 ttys interconnected:
/dev/tnt0 <=> /dev/tnt1
/dev/tnt2 <=> /dev/tnt3
...
/dev/tnt[2n] <=> /dev/tnt[2n+1]
...
/dev/tnt24 <=> /dev/tnt25
the connection is:
TX -> RX
RX <- TX
RTS -> CTS
CTS <- RTS
DSR <- DTR
CD <- DTR
DTR -> DSR
DTR -> CD
For building the module kernel-headers or kernel source are necessary.
Installing linux header for raspbian:
https://gist.github.com/garronej/551aa780f6b4f11788b791c6c578a0ed
Download the tty0tty package from one of these sources: Clone the repo https://github.com/garronej/tty0tty
sudo su
cd /usr/src
git clone https://github.com/garronej/tty0tty
Build the kernel module from provided source
cd tty0tty/module
make
Copy the new kernel module into the kernel modules directory
sudo cp tty0tty.ko /lib/modules/$(uname -r)/kernel/drivers/misc/
Load the module
sudo depmod
sudo modprobe tty0tty
You should see new serial ports in /dev/ (ls /dev/tnt*)
Give appropriate permissions to the new serial ports
sudo chmod 666 /dev/tnt*
You can now access the serial ports as /dev/tnt0 (1,2,3,4 etc) Note that the consecutive ports are interconnected. For example, /dev/tnt0 and /dev/tnt1 are connected as if using a direct cable.
Persisting across boot:
edit the file /etc/modules (Debian) or /etc/modules.conf
nano /etc/modules
and add the following line:
tty0tty
Note that this method will not make the module persist over kernel updates so if you ever update your kernel, make sure you build tty0tty again repeat the process.
In order to build the dkms Debian package
sudo apt-get update && sudo apt-get install -y dh-make dkms build-essential
debuild -uc -us
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