Hardware Reference
In-Depth Information
Chapter 3
Header Strips, LEDs,
and Reset
In this chapter, an inventory of the Raspberry Pi header strips, LEDs, and reset button
connections is covered. These are important interfaces from the Pi to the outside world.
You may want to use a bookmark for Table 3-3 , which outlines the general purpose input/
output (GPIO) pins on header strip P1.
Status LEDs
The Model A Raspberry Pi has a subset of the Model B LED indicators because it lacks the
Ethernet port. The Model B has three additional LEDs, each showing the network status.
Table 3-1 provides a list of LED statuses.
Table 3-1. Status LEDs
LED
Color
Model A
Model B
Comment
ACT
Green
OK
ACT
SD card access activity
PWR
Red
Yes
Yes
Power supply
FDX
Green
N/A
Yes
LAN: Full duplex
LNK
Green
N/A
Yes
LAN: Link
100
Yellow
N/A
100
Labeled incorrectly on Rev 1.0 as
10M: 10/100 Mbit link
OK or ACT LED
This green LED indicates SD card I/O activity. This active low LED is internally driven by
the kernel on GPIO 16 (see the kernel source file bcm2708.c in arm/mach-bcm2708).
 
 
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