GPIOFLICKER(8)

NAME
gpioflicker - link GPIO pin state to network input

SYNOPSIS

gpioflicker [ -frP ] [ -d device ] [ -p pin ] [ -i interface ] [ -t milliseconds ] [ -B basename ] [ -I initial_state ]

DESCRIPTION

gpioflicker changes the state of a GPIO pin on startup, on reception of a signal, or whenever a packet arrives on a network interface. A popular application is to flash GPIO-connected LEDs on firewall systems when packets are blocked.

The default values are suitable for a Soekris Net4501.

The -f (foreground) option keeps gpioflicker from daemonizing itself. Without this option, it will silently detach itself from the controlling terminal and run in the background.

The -r (reverse) option inverts the GPIO pin behavior. Use this on systems where enabling a GPIO pin disables the connected LED (and disabling the pin enables it).

When the -P (pidfile) option is used, gpioflicker will write its process ID to /var/run/gpioflicker.pid. The gpioflicker part of that filename may be set by using the -B (basename) option (which implies -P).

The -d and -p options allow for selecting GPIO device (default: /dev/gpio0) and pin (default: 9).

The -t option sets the number of milliseconds the GPIO pin should be kept active. This defaults to 100.

The -I option sets the initial pin state. A value of 0 deactivates the pin, a value of 1 activates it.

SIGNALS

USR1 activates the GPIO pin, USR2 deacticates it.

SEE ALSO

gpioctl(8).