Hardware Reference
In-Depth Information
GPIO Output: Flashing an LED
For the irst example, you'll need to build a simple circuit consisting of an LED and a resistor.
he LED will provide visual conirmation that the Pi's GPIO port is doing what your Python
program tells it to do, and the resistor will limit the current drawn by the LED to protect it
from burning out.
To assemble the circuit, you'll need a breadboard, two jumper wires, an LED and an appropri-
ate current-limiting resistor (as described in the “Calculating Limiting Resistor Values” side-
bar). Although it's possible to assemble the circuit without a breadboard by twisting wires
together, a breadboard is a sound investment and makes assembling and disassembling pro-
totype circuits straightforward.
Assuming the use of a breadboard, assemble the circuit in the following manner to match
Figure 12-3:
Insert the LED into the breadboard so that the long leg (the anode ) is in one row and
the shorter leg (the cathode ) is in another. If you put the LED's legs into the same row,
it won't work.
Insert one leg of the resistor into the same row as the LED's shorter leg, and the other
resistor leg into an empty row. he direction in which the resistor's legs are placed
doesn't matter, as a resistor is a non-polarised (direction-insensitive) device.
Using a jumper wire, connect Pin 11 of the Raspberry Pi's GPIO port (or the corre-
sponding pin on an interface board connected to the GPIO port) to the same row as
the long leg of the LED.
Using another jumper wire, connect Pin 6 of the Raspberry Pi's GPIO port (or the cor-
responding pin on an interface board connected to the GPIO port) to the row that
contains only one leg of the resistor and none of the LED's legs.
Be very careful when connecting wires to the Raspberry Pi's GPIO port. As discussed earlier in
the chapter, you may do serious damage to the Pi if you connect the wrong pins.
WARNING
 
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