devices.md

Devices handling

Location

All devices can be found under /dev and they are created by kernel modules. /dev files are virtual, and they are called character devices.

They communicate through /sys virtual filesystem.

RAM

To know the RAM type and size:

sudo dmidecode --type 17

Serial communication

The serial ports start with tty and serial prefixes under /dev directory. Useful tools for serial communication are:

minicom -s # configure service and then launch minicom
minicom
minicom -D /dev/ttyS0 # overwrite device port
minicom -C capture.log -D /dev/ttyS0 # to capture strings from serial port
CTRL + A -> q to exit

cu -l /dev/<device> -s <baud rate speed>
cu -l /dev/ttyS0 -s 921600

screen /dev/<device> <speed>,<packet type>
screen /dev/ttyS0 19200,cs8

To setup a serial port:

stty -F /dev/ttyS0 speed 921600 cs8

Create a serial loopback (/dev/serloop0 echo /dev/serloop1):

socat -d -d pty,raw,echo=0,link=/dev/serloop0 \
            pty,raw,echo=0,link=/dev/serloop1

GPIO communication

The following example is using /sys/class virtual filesystem to communicate with GPIO0:

cd /sys/class/gpio    // enter the gpio class interface
echo 0 > export       // create the gpio0
cd gpio0              // enter the gpio0 class
echo out > direction  // select the gpio0 direction
echo 1 > value        // set gpio0 output value to 1

USB

To get the vendor/product ID:

sudo cat /sys/kernel/debug/usb/devices | grep -E "^([TSPD]:.*|)$"