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by rpdom
Fri Jan 19, 2018 5:56 am
Forum: Teaching and learning resources
Topic: Super-cheap Computing Cluster for Learning
Replies: 21
Views: 1331

Re: Super-cheap Computing Cluster for Learning

I believe a non-powered hub may be used instead of a powered hub. It would be great if someone on this forum could confirm that the following setup works. First, power the Pi B+, 2B or 3B directly from a sufficient power supply. Enable max_usb_current=1 in /boot/config.txt and then connect the Zero...
by rpdom
Thu Jan 18, 2018 9:24 pm
Forum: General discussion
Topic: Pi zero video output
Replies: 2
Views: 66

Re: Pi zero video output

How about bare wires connected to the TV pin holes on the Zero -> RCA

That cable is unlikely to work. The TV connections already provide composite video output which should be compatible with RCA video inputs.
by rpdom
Thu Jan 18, 2018 9:14 pm
Forum: Beginners
Topic: Understanding Micro SD Cards, NOOBS, Booting, Saving
Replies: 3
Views: 55

Re: Understanding Micro SD Cards, NOOBS, Booting, Saving

1. Some people seem to have more than one Micro SD Card. Does Noobs have to be on each one? No. If you only have one OS on a card you don't need NOOBS on it at all. The installation procedure is different and it will use a bit less space without NOOBS. 2.Presumably the cards can't be interchanged w...
by rpdom
Thu Jan 18, 2018 8:27 pm
Forum: Advanced users
Topic: SSD drive boot experience ??
Replies: 3
Views: 77

Re: SSD drive boot experience ??

I have also updated internal fw of Pi to latest one, same for raspbian (I have one on a SD card) and have setup fw to boot in USB mode. There is no internal firmware on the Pi. It is all held on the SD card or USB/network storage (for the Pi 3B/2Bv2). I presume you have set the one-time option to e...
by rpdom
Thu Jan 18, 2018 6:47 am
Forum: Bare metal
Topic: GPIO pull up resisance
Replies: 15
Views: 18304

Re: GPIO pull up resisance

I'm pretty certain that the 50mA recommendation was based on the old 3v3 linear regulator on the original Pi. The newer ones (B+ and later) use a more efficient switching regulator and can supply much more current. I haven't seen an actual recommended maximum, but I believe it can supply over 100mA ...
by rpdom
Wed Jan 17, 2018 6:56 pm
Forum: Troubleshooting
Topic: Reading GPIO states via web interface - php
Replies: 2
Views: 70

Re: Reading GPIO states via web interface - php

You can get the current value like this

Code: Select all

$status = shell_exec("/usr/local/bin/gpio -g read 17");
$status will now contain 1 (on) or 0 (off).
by rpdom
Tue Jan 16, 2018 6:46 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 1-wire DS18B20 disappears
Replies: 41
Views: 2750

Re: 1-wire DS18B20 disappears

The recommended pull-up on the datasheet for the DS18B20 is 5K. The closest common resistor to that is the 4K7. Best to stick with that (although I have used two 10K resistors in parallel when I didn't have a 4K7 to hand).
by rpdom
Tue Jan 16, 2018 9:02 am
Forum: Beginners
Topic: Connecting many sensors, and some advice might help :)
Replies: 3
Views: 103

Re: Connecting many sensors, and some advice might help :)

that page said "Also make sure your Raspberry Pi is running the latest Raspbian Jessie operating system (either the full or lite version) before starting the guide." it only work with raspi Jessie OS? instead of other OS like 10 IoT ? That guide is a bit out of date. You should use the latest Raspb...
by rpdom
Tue Jan 16, 2018 8:09 am
Forum: Beginners
Topic: rp 0 sudo apt-get upgrade results in an error
Replies: 1
Views: 90

Re: rp 0 sudo apt-get upgrade results in an error

Seek and ye shall find... it is a problem that others have encountered. Try the fix mentioned here viewtopic.php?f=28&t=202523
by rpdom
Mon Jan 15, 2018 9:50 pm
Forum: General discussion
Topic: Most advisable lightweight Web server
Replies: 7
Views: 266

Re: Most advisable lightweight Web server

Nginx is good for reverse proxy. I don't thing lighttpd can do that.
by rpdom
Mon Jan 15, 2018 9:40 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 1-wire DS18B20 disappears
Replies: 41
Views: 2750

Re: 1-wire DS18B20 disappears

What kind of divider resistor. how big are your resistors. You know that a resistor divider could be reduce by thevenin theorem. You will get 3.3V but you add a resistor in series and this could be your problem. Is the resistor divider only on the power pin or you have the same thing on the data pi...
by rpdom
Mon Jan 15, 2018 9:12 pm
Forum: Troubleshooting
Topic: cannot ssh into my raspberry pi zero W
Replies: 22
Views: 355

Re: cannot ssh into my raspberry pi zero W

robjak wrote:
Mon Jan 15, 2018 7:16 pm
~ $ sudo apt-get install --reinstall openssh-server

my bad, thought it was just openssh.
Mine too. I didn't bother to check. I thought there was an openssh meta-package that installed the openssh-server and openssh-client packages.
by rpdom
Mon Jan 15, 2018 8:58 pm
Forum: General discussion
Topic: Failing USB hard drive
Replies: 40
Views: 864

Re: Failing USB hard drive

Try sticking the failed drive in a freezer for a few hours, then see if it works. It may get it going for long enough for you to get some data off it. I've done this with some failed drives in the past and have had some success.
by rpdom
Mon Jan 15, 2018 8:31 am
Forum: Troubleshooting
Topic: cannot ssh into my raspberry pi zero W
Replies: 22
Views: 355

Re: cannot ssh into my raspberry pi zero W

The package is called openssh, not openshh.
by rpdom
Sun Jan 14, 2018 5:30 pm
Forum: Beginners
Topic: In which order does a Python Program run
Replies: 18
Views: 458

Re: In which order does a Python Program run

However, the mention of BBC BASIC reminds me of an important difference in the way DEF works. You define procedures outside your normal flow, such as after END, and the PROC statement magically finds them: 10 PROChello 20 END 30 : 40 DEF PROChello 50 PRINT "hello" 60 ENDPROC If you try to define a ...
by rpdom
Sun Jan 14, 2018 4:38 pm
Forum: Graphics, sound and multimedia
Topic: HDMI and Composite simultaneous video
Replies: 3
Views: 132

Re: HDMI and Composite simultaneous video

No. It is not possible. It is a hardware limitation.
by rpdom
Sun Jan 14, 2018 4:29 pm
Forum: Python
Topic: Can't run a script on startup with /etc/rc.local
Replies: 3
Views: 3229

Re: Can't run a script on startup with /etc/rc.local

Are you replying to a four year old post just to publicise your you tube video?
by rpdom
Sun Jan 14, 2018 3:34 pm
Forum: General programming discussion
Topic: Is there anything wrong with this bash script (timelapse)?
Replies: 6
Views: 131

Re: Is there anything wrong with this bash script (timelapse)?

sbaratheon wrote:
Sun Jan 14, 2018 2:47 pm
I was under the impression that $SECONDS was an internal variable (http://tldp.org/LDP/abs/html/internalvariables.html)
It is. But you might want to set it to zero at the start.
by rpdom
Sun Jan 14, 2018 2:09 am
Forum: General programming discussion
Topic: ls question (I'm so embarassed..)
Replies: 2
Views: 134

Re: ls question (I'm so embarassed..)

In that particular instance you are looking at a device file, not a normal file. Device files are identified by a Major and Minor device number. The first number 250 is the major number, the second number 0 is the minor number. One example of this is your SD card, where on a standard (non-NOOBS) Ras...
by rpdom
Sat Jan 13, 2018 8:09 pm
Forum: Advanced users
Topic: [SOLVED] RPi 3 MPG2 code not activating
Replies: 6
Views: 138

Re: RPi 3 MPG2 code not activating

How much memory is allocated to the GPU? vcgencmd get_mem gpu
It needs to be about 64MB or higher for the codec to activate.
by rpdom
Sat Jan 13, 2018 8:29 am
Forum: Raspbian
Topic: Tutorial: Compile VLC with HW acceleration - Stretch, RPi 2/3
Replies: 50
Views: 8590

Re: Tutorial: Compile VLC with HW acceleration - Stretch, RPi 2/3

For this sort of thing I would use omxplayer with h264 video and the --loop option. I've had a video of that form running continuously for a few months on a Pi (I'd switched the screen off and forgotten it was running) with no problems at all. (It was a 4 hour long video of a log fire that I downloa...
by rpdom
Fri Jan 12, 2018 8:47 pm
Forum: Off topic discussion
Topic: theft mode
Replies: 3
Views: 298

Re: theft mode

Translation error, perhaps.

What was the exact full wording of the message?
by rpdom
Fri Jan 12, 2018 8:10 pm
Forum: General discussion
Topic: entertainment
Replies: 5
Views: 212

Re: entertainment

But, we did have a metal shop kitted out with a couple of industrial sized lathes, a milling machine, a shaper, a forge and all kind of other tools. We could even make aluminium castings. Then there was the wood shop. It was worth the incarceration to be able to use those facilities for some hours ...
by rpdom
Fri Jan 12, 2018 7:19 pm
Forum: Troubleshooting
Topic: Extremely hot SD card/reader
Replies: 4
Views: 133

Re: Extremely hot SD card/reader

There have been a few reports over the years of SD cards overheating or melting. In PCs as well as Pi.
by rpdom
Fri Jan 12, 2018 6:47 am
Forum: Troubleshooting
Topic: raspi-config options missing
Replies: 5
Views: 2035

Re: raspi-config options missing

Just FYI I was looking for the same items as OP, i see the answer must have been correct as at Feb 2017, I have just installed Raspian Stretch and I cannot find the option to enable Device Tree.. has this had a name change? There is no option to enable Device Tree. It is always enabled now. sorry f...

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