Hardware Reference
In-Depth Information
Figure 1-3.
The “rainbow” screen (uploaded to
http://elinux.org/File:Debug-screen.jpg
by user Popcorn-
mix and shared under the terms of the Creative Commons Attribution-ShareAlike 3.0 Unpor-
ted License)
Some optional versions exist for some of the Raspberry Pi firmware files. It is possible
to configure the Raspberry Pi to dedicate the minimum amount of memory to the GPU
(16 MB). When this is done, the Raspberry Pi Second Stage Bootloader looks for
start_cd.elf
and
fixup_cd.dat
instead of
start.elf
and
fixup.dat
.
Hack #24
provides
a longer discussion on GPU/CPU memory splitting.
Monitor the Raspberry Pi Hardware
HACK 05
Worried that your Pi is throwing wild parties while you're out of the house?
Here's how to point a webcam at it and stream the video to the Internet.
Just kidding! These tools can monitor the physical state of your tiny
hardware.
A “normal” Linux computer would likely include onboard health monitoring sensors.
Quite a few monitoring chips and components are used in various systems, but on the
Raspberry Pi, all of that hardware is entirely hidden inside the Broadcom system-on-
chip, so you can't access it with those usual methods.
To reach those components to monitor your Pi's health, you need to use the
vcgencmd
utility. It should be preinstalled with any of the general-purpose Raspberry Pi Linux
distributions available, but if it's not, you can get a copy from the firmware tree at
https://github.com/raspberrypi
. If your distribution is compiled for ARM hardware
floating point, look in the
hardfp/
subdirectory; otherwise, look in the
opt/
subdirec-
tory.
Checking for Hard Float
At the time of this writing, most Linux distributions (including Pidora, Rasp-
bian, Occidentalis, OpenELEC, and RaspBMC) are built for the ARMv6 hard-
float architecture, because that gives the best possible performance on the
Raspberry Pi. However, some older releases of these targets (and other OS
platforms) were built with optimization for ARMv6 soft-float. These two op-
