Hardware Reference
In-Depth Information
Option measure_clock
This firmware access option provides the user with clock rate information, according
to the argument appearing after
measure_clock
. Valid values for
<clock>
are listed in
Table
4-2
.
vcgencmd measure_clock <clock>
Table 4-2.
Valid Arguments for the
measure_clock
Option
Clock
Description
arm
ARM CPU
core
Core
dpi
Display Pixel Interface
emmc
External MMC device
h264
h.264 encoder
hdmi
HDMI clock
isp
Image Sensor Pipeline
pixel
Pixel clock
pwm
Pulse Width Modulation
uart
UART clock
v3d
Video 3D
vec
The following shell script is often used to list all available clocks:
$ for src in arm core h264 isp v3d uart pwm emmc pixel vec hdmi dpi ; do
echo −e "$src : $(vcgencmd measure_clock $src)" ;
done
Here is the example output:
arm : frequency (45)=700074000
core : frequency (1)=250000000
h264 : frequency (28)=250000000
isp : frequency (42)=250000000
v3d : frequency (43)=250000000
uart : frequency (22)=3000000
pwm : frequency (25)=0
emmc : frequency (47)=100000000
