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by cnt
Fri Jan 31, 2014 5:27 am
Forum: Troubleshooting
Topic: Headless pi not coming back after update -> upgrade
Replies: 5
Views: 872

Re: Headless pi not coming back after update -> upgrade

Odd. I dug up a keyboard and HDMI cable, rebooted and was presented with the raspi-config screen, which i guess runs after initial install. After exiting the config screen and rebooting everything works as it should. My problem is very reproducible though and this really shouldn't happen. especially...
by cnt
Thu Jan 30, 2014 7:11 am
Forum: Troubleshooting
Topic: Headless pi not coming back after update -> upgrade
Replies: 5
Views: 872

Headless pi not coming back after update -> upgrade

For whatever reason I get a connection timed out (rather than refused) when trying to connect to my raspberry pi after apt-get update; apt-get upgrade. Here's what I'm doing: 1) I have a Raspberry pi B with camera module 2) i'm flashing the latest raspbian (2014-01-07) 3) boot, ssh in, 'apt-get upda...
by cnt
Wed Nov 27, 2013 5:04 am
Forum: Wolfram Language
Topic: Any Tutorial for Wolfram?
Replies: 7
Views: 20723

Re: Any Tutorial for Wolfram?

For those already somewhat familiar with mathematica (and, i guess, by extension the wolfram language) here's the language (as opposed to mathematica) documentation: http://reference.wolfram.com/language/ as well as the raspberry pi specific section http://reference.wolfram.com/language/guide/Raspbe...
by cnt
Sat Mar 02, 2013 6:29 pm
Forum: General discussion
Topic: can the pi do "software serial"?
Replies: 10
Views: 16641

Re: can the pi do "software serial"?

with raspbian or another "standard" linux? no. The problem is that linux is not a real-time operating system. What that means is that you get no guarantees about timing. So, if your program was preempted during serial communication it may miss incoming bits or corrupt outgoing bytes. it is possible ...
by cnt
Sat Feb 23, 2013 7:33 pm
Forum: Advanced users
Topic: using /dev/ttyAMA0 as PTT like normal serial with DTR
Replies: 2
Views: 2825

Re: using /dev/ttyAMA0 as PTT like normal serial with DTR

I don't work with ham modems but i'm going to guess that they take RS-232 levels (-/+12v) not ttl levels. it may be easier to just get a usb to serial dongle. If you've got the logic levels worked out and are dead set on using GPIO you can set GPIO17 on pin 11 to alt function 3, which is RTS. Then y...
by cnt
Fri Feb 15, 2013 11:25 pm
Forum: General discussion
Topic: 2013-02-09-wheezy-raspbian changelog
Replies: 2
Views: 1875

2013-02-09-wheezy-raspbian changelog

I've been having trouble finding whats different with the newest raspbian image.
Is there a changelog? In the past there has been a main page update for new images but I guess they're not doing that anymore.
by cnt
Thu Jan 31, 2013 4:27 am
Forum: General discussion
Topic: update the FAQ
Replies: 0
Views: 336

update the FAQ

Specifically the question: What hardware documentation will be available? Broadcom don’t release a full datasheet for the BCM2835, which is the chip at the heart of the Raspberry Pi. We will release a datasheet for the SoC which will cover the hardware exposed on the Raspi board e.g. the GPIOs. We w...
by cnt
Mon Jan 21, 2013 8:12 am
Forum: General discussion
Topic: powering USB peripherals
Replies: 5
Views: 980

Re: powering USB peripherals

I actually have three of those same regulators (from another seller i think) and they work surprisingly well but they do get hot when you run up against 2A. Adding a heatsink may be a good idea.
by cnt
Mon Jan 21, 2013 8:08 am
Forum: Beginners
Topic: startup script in the fat partition
Replies: 9
Views: 1577

Re: startup script in the fat partition

Sorry. I think people are misinterpreting my posts. For some reason it got moved from suggestions to basic setup, which is the wrong place. I am /completely/ aware of my other options. Imaging 20 pi's is actually slower than logging into 20 pies over serial and changing scripts. Our institution does...
by cnt
Sat Jan 19, 2013 7:30 pm
Forum: Beginners
Topic: startup script in the fat partition
Replies: 9
Views: 1577

Re: startup script in the fat partition

yes. I really don't have access to any partition but /boot without asking a bunch of students to hassle with weird 3rd party software on windows. I also don't want to write a set of instructions for every OS being used by students. Just being able to say "here's a 1kb file, put it on yours SD card b...
by cnt
Wed Jan 16, 2013 9:03 pm
Forum: Beginners
Topic: startup script in the fat partition
Replies: 9
Views: 1577

startup script in the fat partition

I recall that an earlier Rasbian image had a startup script that was easily changeable because it was in the fat (/boot) partition. I recently had to go around a class room and login over serial to a dozen rpis to change the wifi config file so students could connect to the wifi and log into their h...
by cnt
Tue Jan 15, 2013 7:05 am
Forum: General discussion
Topic: Close up of the Raspberry Pi
Replies: 2
Views: 624

Re: Close up of the Raspberry Pi

flagstone78 wrote:Just a question. Does anyone know what the small holes by the p2/p3 are for?
Nice photo by the way. Definitely is going to be my background.
do you mean the 100mil space through holes? Those are for headers; I think for JTAG IIRC.
by cnt
Tue Jan 15, 2013 7:03 am
Forum: General discussion
Topic: Clockspeed question
Replies: 2
Views: 567

Re: Clockspeed question

yah. try

Code: Select all

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
by cnt
Mon Jan 07, 2013 5:36 am
Forum: Beginners
Topic: Problems setting up Pi
Replies: 11
Views: 1108

Re: Problems setting up Pi

sounds like its rebooting in a loop. I'd make sure you're not dropping too much voltage across your cable or the polyfuse. Sadly 99% of problems come from power. Maybe try with just power and HDMI plugged in and see if it boots all the way.
by cnt
Mon Jan 07, 2013 5:32 am
Forum: Beginners
Topic: connecting RPI to internet via USB port
Replies: 1
Views: 483

Re: connecting RPI to internet via USB port

In general it's a good idea to keep your topics to ONE forum at a time.
by cnt
Mon Jan 07, 2013 5:20 am
Forum: General discussion
Topic: RasPi Bramble Cluster
Replies: 1
Views: 742

Re: RasPi Bramble Cluster

Very much an amateur but i am interested to know if running 2-4 RasPi's in a cluster to run a minecraft server would work and if it would be worth it, looking to replace my current server computer, not very energy efficient, its not only a minecraft server but minecraft being the most intensove ser...
by cnt
Fri Jan 04, 2013 7:41 am
Forum: Beginners
Topic: 16th Dec Wheezy
Replies: 2
Views: 558

Re: 16th Dec Wheezy

I think the only change was they added the raspberry pi store. I'm sure you have the most recent version.
by cnt
Fri Jan 04, 2013 7:39 am
Forum: Beginners
Topic: Python Libraries, Hardware I/O map or schematic
Replies: 2
Views: 910

Re: Python Libraries, Hardware I/O map or schematic

there are some terse examples here along with a pinout: http://elinux.org/RPi_Low-level_peripherals I'm not sure what you mean by schematic of io pins. They're all broken out SoC pins; nothing special except the I2C pins have 1.8k pull ups. IIRC you can get something like 7mA out of each gpio pin so...
by cnt
Fri Jan 04, 2013 7:29 am
Forum: General discussion
Topic: best wifi dongle
Replies: 18
Views: 8284

Re: best wifi dongle

I use this one AirLink101 AWLL5088 : http://www.amazon.com/dp/B003X26PMO It's tiny, doesn't block the other usb port, uses <100mA (according to my bench top PSU the whole pi with wifi usses < 500mA) and has drivers included with the current raspbian. oh yah and 12$ will amazon prime shipping is nice...
by cnt
Sun Dec 23, 2012 6:43 am
Forum: Advanced users
Topic: Preferred USB > RS232 dongles and drivers?
Replies: 5
Views: 2585

Re: Preferred USB > RS232 dongles and drivers?

I was thinking about that but I'm not sure if one can directly access the CPU's I/O in PHP? sure it can. Its under /dev/ttyAMA0 and can be used like any serial port on any other linux computer (from the software point of view, not electrically of course.) If you want more than one serial port a USB...
by cnt
Sun Dec 23, 2012 6:33 am
Forum: General discussion
Topic: Building a 5v UPS using LM317 IC. Help needed.
Replies: 33
Views: 13818

Re: Building a 5v UPS using LM317 IC. Help needed.

as others suggested you can't really use a linear regulator unless you use one with an extremely low dropout. What I would suggest is using a 12v battery and getting a 5v DC out switching power supply. If you're willing to wait on shipping from china you can get them for as low as 2-3$ each.
by cnt
Sat Dec 22, 2012 9:02 pm
Forum: Troubleshooting
Topic: Raspberry Pi not booting wierd voltage reading
Replies: 11
Views: 1575

Re: Raspberry Pi not booting wierd voltage reading

the only thing that could cause that is a bad power supply. I have no idea how tolerant the rpi is to over voltage but that is not a good sign :(
by cnt
Sat Dec 22, 2012 8:40 pm
Forum: General discussion
Topic: Hardware: Crystal Oscillator - Accuracy?
Replies: 3
Views: 5506

Re: Hardware: Crystal Oscillator - Accuracy?

according to the schematic ( http://www.raspberrypi.org/wp-content/uploads/2012/10/Raspberry-Pi-R2.0-Schematics-Issue2.2_027.pdf) ) the oscilator is 19.2Mhz not 25. I think your looking at the crystal for the ethernet. A cheap crystal (which the rpi probably has to keep costs down) has a typical err...
by cnt
Sat Dec 22, 2012 9:04 am
Forum: Troubleshooting
Topic: wifi AirLink101 AWLL5088 (RTL8188CUS) not working
Replies: 1
Views: 625

Re: wifi AirLink101 AWLL5088 (RTL8188CUS) not working

never mind. it works when run wpa_gui as root.
by cnt
Sat Dec 22, 2012 8:20 am
Forum: Troubleshooting
Topic: wifi AirLink101 AWLL5088 (RTL8188CUS) not working
Replies: 1
Views: 625

wifi AirLink101 AWLL5088 (RTL8188CUS) not working

I bought the AirLink101 AWLL5088 because I had read threads that it works with the raspberry pi right out of the box. Unfortunately i'm having trouble with it. when I run wpa_gui I get nothing under the adapter drop down, so obviously I can't find any networks. If anyone has any ideas that would be ...

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