Hardware Reference
In-Depth Information
Each option in
config.tx
t should be on its own line, with the option name followed by an
equals sign (
=
) and then the required value. For example, to tell the Pi to use a PAL-format
analogue TV with a 4:3 aspect ratio and a 20-pixel overscan on all sides, put the following
lines into
config.txt
:
sdtv_mode=2
sdtv_aspect=1
overscan_left=20
overscan_right=20
overscan_top=20
overscan_bottom=20
To tell the Pi to use a DVI display through the HDMI port in the 720p60 format with no
overscan at all, use the following values instead:
hdmi_group=1
hdmi_mode=4
hdmi_drive=1
disable_overscan=1
For the changes to take efect, the Pi must be restarted. If you ind that your changes have
disabled the Pi's video output on your monitor, simply insert the SD card into another com-
puter and either modify the
config.txt
ile with new settings or delete it altogether to
restore the defaults.
Boot Options
he
config.txt
ile can also be used to control how Linux is loaded on the Raspberry Pi.
Although the most common method for controlling the loading of the Linux kernel is to use
a separate ile called
cmdline.txt
(which you'll learn about later in this chapter), it is pos-
sible to use just
config.txt
. he following options control the boot process:
❍
disable_commandline_tags
—his tells the
start.elf
module (discussed later in
this chapter) to skip illing in memory locations past 0x100 before loading the Linux
kernel. his option should not be disabled, as doing so can cause Linux to load incor-
rectly and crash.
❍
cmdline
—he command line parameters to be passed to the Linux kernel. his can be
used in place of the
cmdline.txt
ile, usually found in the
/boot
directory.
