Basic led control using simple commands.
GPIO is manage using python scripts

piget-core

Type this command in your terminal

/pi/install led

By default, the green led (ACT led) light up when data is read or write on the SD card. Here is how to control it :

• Turn on LED: /pi/ledOn
• Turn off LED: /pi/ledOff
• Blink LED: /pi/ledBlink
• Return LED to normal state: /pi/ledReset

Here is how to plug a led on GPIO 21

• Wire the LED + (the longest leg) on pin 21
• Wire the LED - on a (at least 100 ohms) resistor
• Wire the resistor to the ground, next to pin 21.

If you want to plug a led on another pin, there is a list on http://pinout.xyz

You can find which resistor you need for your led on : http://led.linear1.org/1led.wiz

Here is a list of commands

• Turn on LED: /do/led/on 21
• Turn off LED: /do/led/off 21
• Blink LED: /do/led/blink 21
• Change led intensity: /do/led/pulse 21
• Display state of led (0:off 1:on): /do/led/state 21
• Display gpio: /show/gpio

You can use additional arguments on some commands.
/do/led/blink

/do/led/blink   pin    number_of_blink
/do/led/blink 21 5

/do/led/blink   pin    number_of_blink    speed (in seconds)
/do/led/blink 21 5 0.05

/do/led/pulse

/do/led/pulse   pin    speed
/do/led/pulse 21 0.3