Difference between revisions of "Hardware: Raspberry Pi"

Revision as of 23:19, 30 October 2013

Just few notes about Raspberry Pi ...

Power

According to details from RPi project voltage between 4.75 and 5.25 volts is fine. I personally preffer voltage between 4.80 and 5.00 volts. Voltage below 4.8 volts, can lead to instability of 3v3 regulator (RG2) (e.g. CPU power source) and connected equipment. Voltage above 5.00 (5.25) can shorten life of board and lead to problems with connected equipment. Voltage above 5.6V trip D17 over voltage protection diode. Make sure that connected USB hub (if any) is not back feeding power. It can cause serious problems as there is no protection on USB output ports.

If you are experiencing random USB device disconnects, repeating keys from keyboard or random reboots (hung) of board then there is something wrong with power source. I think USB charger as source was not so good decision as most of the chargers drop voltage up on power demand. This can lead to under voltage and cause stability problems. If you hit some of them, then try to measure voltage between test points or change power source.

My Raspberry Pi is running pretty stable with following power sources:

• RASPBERRY PI PSU is only 1A PSU, so no "hungry" devices. I Have ADATA N005 64GB USB flash disk + receiver for air mouse connected and it is just fine.
• Powerocks Stone 3 bílá this can act as UPS, but there is still question what is impact of this usage on battery. Only this device provide power at almost exactly 5.00 volts also under load
• Gembird the name state "Gembird" but it is "energenie". This source is also fine, but without load it is providing approximately 5.20 V which is so close to upper limit. Additionally it is noisy without load. It is working but i don't recommend it.

Boot configuration

Raspberry Pi don't have so called "BIOS" and it's configuration interface. Configuration of CPU, GPU and board is stored in /boot/config.txt. If you have problem with overscan or screen resolution then You can resolve it by modification of this file. For example I have one RPi connected to old television and this television don't use overscan only if output of RPi is in DMT / PC mode. My boot config for Raspbmc is:

# default Raspbmc config
arm_freq=800
force_turbo=1
gpu_mem=128
disable_overscan=1
start_file=start_x.elf
fixup_file=fixup_x.dat
# My configuration:
# Set stdv mode to PAL (as used in Europe)
sdtv_mode=2
# Force the monitor to HDMI mode so that sound will be sent over HDMI cable
hdmi_drive=2
# Set monitor mode to DMT
hdmi_group=2
# Set monitor resolution to 1360x768  60Hz
hdmi_mode=39

More details can be found on elinux.org in section RPi_config.

nfs

TODO: ... mount options

ro,bg,hard,rsize=32768,wsize=32768,vers=3,tcp

Temperature

I was trying to get clear answer "what is safe temperature" for Raspberry Pi and apparently there is no clear statement. From my findings safe temperature is up to 60C and shutdown temperature should be 70C. Although it looks like RPi can run up to 80C running close to this temperature can reduce board lifetime. Current temperature measured by CPU itself can be displayed by vcgencmd command or by direct read from /proc file system.

$ vcgencmd measure_temp
temp=54.1'C

FYI 1: original plastic case with ventilation opening in RPi logo is concentrating heat. If i open this case temperature drop for more that 10C.

FYI 2: small "ram" heatsink don't change temperature too much especially if adhesive side is cheaper with significant thermal resistance. I tried several heatsinks and result was only 2 to 5 degree Celsius temperature drop.