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by Douglas6
Sat Oct 26, 2013 2:36 pm
Forum: Automation, sensing and robotics
Topic: I2C temperature sensor for beginners help needed
Replies: 6
Views: 7413

Re: I2C temperature sensor for beginners help needed

Someone please correct me if I'm wrong, but I'm pretty sure that you don't need external resistors on the Pi's SDA and SCL lines. The Pi has internal 1k8 pull-ups on these pins. I've hacked a couple i2c circuits, with chained slaves, and never used external pull-ups nor had any problems. http://elin...
by Douglas6
Sat Oct 26, 2013 2:37 am
Forum: Beginners
Topic: Single Webpage
Replies: 5
Views: 874

Re: Single Webpage

Python has a built-in HTTP server class, SImpleHTTPServer (in 2.7) that might be the easiest way to do what you want. See http://docs.python.org/2/library/simplehttpserver.html and Google for some code examples.
by Douglas6
Fri Oct 25, 2013 5:29 pm
Forum: General discussion
Topic: Device which shuts down the Raspberry Pi if Voltage is low
Replies: 23
Views: 12580

Re: Device which shuts down the Raspberry Pi if Voltage is l

That should work to shut down the Pi gracefully. But I think your problem is restarting the Pi. When the Pi is shutdown, it doesn't power off (red light stays on, but the OS is not running) unless power is lost completely. So you still need 'somebody' else to wake it up at the appropriate time (when...
by Douglas6
Fri Oct 25, 2013 4:11 pm
Forum: Other projects
Topic: The Power Cycler
Replies: 10
Views: 1947

Re: The Power Cycler

Glad to hear that I (well, Lady Ada and Mister Savage) could help. And did this fix your wonky satellite modem problem?
by Douglas6
Tue Oct 22, 2013 7:36 pm
Forum: General discussion
Topic: Device which shuts down the Raspberry Pi if Voltage is low
Replies: 23
Views: 12580

Re: Device which shuts down the Raspberry Pi if Voltage is l

Using a ATiny85 chip seems a bit excessive for monitoring the supply voltage but then again why not I suppose. :) I agree. :) Full disclosure; I'm a programmer, not an electronics guy, so setting a threshold by typing in a number comes much more naturally to me than "tweaking the Vdd supply rail" :...
by Douglas6
Tue Oct 22, 2013 5:09 pm
Forum: General discussion
Topic: Device which shuts down the Raspberry Pi if Voltage is low
Replies: 23
Views: 12580

Re: Device which shuts down the Raspberry Pi if Voltage is l

"At 8 MHz the current draw is about 9 milliamps. That number includes the green power LED which draws about 3mA so thats 6mA for the microcontroller itself." Not excessive, I don't think. especially if that power LED can be yanked. But I realize this may be more of a learning experience than a pract...
by Douglas6
Tue Oct 22, 2013 4:25 pm
Forum: General discussion
Topic: Device which shuts down the Raspberry Pi if Voltage is low
Replies: 23
Views: 12580

Re: Device which shuts down the Raspberry Pi if Voltage is l

I'm afraid I'm still in the conceptual phase of this project (and learning EVERYTHING as I go, like, how to use a multimeter). But the idea is simple: Connect the battery+ to an analog pin on the Trinket, connect a digital pin on the Trinket to a GPIO on the Pi through a voltage divider. Connect up ...
by Douglas6
Mon Oct 21, 2013 5:25 pm
Forum: Java
Topic: RPi and Arduino over RXTX Java
Replies: 3
Views: 3447

Re: RPi and Arduino over RXTX Java

Sorry, I have no experience with the RXTX library. The folks at StackOverflow seem to have a low opinion of it, and some suggest jSSC http://code.google.com/p/java-simple-serial-connector/ instead, and that appears to have been tested on the Pi. On the other hand, I think the Arduino IDE uses RXTX, ...
by Douglas6
Mon Oct 21, 2013 12:38 pm
Forum: General discussion
Topic: Device which shuts down the Raspberry Pi if Voltage is low
Replies: 23
Views: 12580

Re: Device which shuts down the Raspberry Pi if Voltage is l

I'm working on using a microcontroller to monitor voltage, drive an LED fuel gauge, and alert the Pi if it's getting low. Seems like overkill, but $8 bucks for a Trinket (an ATiny85 with a bootloader on a breakout board) is cheaper and easier for the electronically challenged (me) than a bunch of di...
by Douglas6
Sun Oct 20, 2013 11:27 pm
Forum: Graphics, sound and multimedia
Topic: Pianobar & LIRC
Replies: 6
Views: 1740

Re: Pianobar & LIRC

[Edit: Grrrr, the code tags aren't working tonight, sorry about that] Ok, you didn't mention at which point you're struggling, so let's make sure the basics are set up correctly. 1. You should be able to type 'pianobar' in a terminal window to start pianobar. It will then ask you to select a station...
by Douglas6
Sun Oct 20, 2013 5:09 pm
Forum: Other projects
Topic: The Power Cycler
Replies: 10
Views: 1947

Re: The Power Cycler

You might consider a different power switching solution that can be controlled from a GPIO pin. Adafruit has this http://www.adafruit.com/products/268 for $26US.
by Douglas6
Sun Oct 20, 2013 2:56 pm
Forum: Automation, sensing and robotics
Topic: Sonic Screwdriver Raspberry Pi?
Replies: 3
Views: 2739

Re: Sonic Screwdriver Raspberry Pi?

I found it rather easy to use an IR remote to make the Pi do my bidding, using irexec and an lircrc configuration file to run my own scripts responding to remote keypresses. There's a basic write-up at http://www.dkographicdetails.com/myPi/?p=20
by Douglas6
Fri Oct 18, 2013 1:53 pm
Forum: Beginners
Topic: Retrieving current servo position
Replies: 3
Views: 756

Re: Retrieving current servo position

Also, Adafruit sells these http://www.adafruit.com/products/1449, which do allow for feedback of the current position via the internal potentiometer.
by Douglas6
Wed Oct 16, 2013 8:42 pm
Forum: Other projects
Topic: Safely discharge a LiPo cell
Replies: 3
Views: 980

Re: Safely discharge a LiPo cell

Thank you for the sanity check, I will proceed with caution. The cell has protection circuitry built in, and the boost converter I'll be using has Under Voltage Lock Out also, so I should be good there, but that's one of the things I want to test with a dummy load. And yes, I'll be keeping an eye (w...
by Douglas6
Wed Oct 16, 2013 8:02 pm
Forum: Java
Topic: Java NetBeans or Eclipse on Raspberry Pi
Replies: 16
Views: 13685

Re: Java NetBeans or Eclipse on Raspberry Pi

I gotta agree with Simon; the "right" way would be to have some mock classes and maybe an IOC framework like Spring, and do as much building and testing off of the Pi as possible. I mean, this IS Java, after all. My current project makes heavy use of an LCD and input buttons, and I just haven't gott...
by Douglas6
Tue Oct 15, 2013 5:47 pm
Forum: Java
Topic: Java NetBeans or Eclipse on Raspberry Pi
Replies: 16
Views: 13685

Re: Java NetBeans or Eclipse on Raspberry Pi

An alternative that I use is to run Eclipse on the PC, and access my project code on the Pi's SD card via a Samba share. Advantage, no need to build a jar and copy it on each cycle (Eclipse happily builds the project in-place, on the Pi). Disadvantage, Eclipse gets very confused if the project is op...
by Douglas6
Mon Oct 14, 2013 4:52 pm
Forum: Other projects
Topic: Safely discharge a LiPo cell
Replies: 3
Views: 980

Safely discharge a LiPo cell

I'm looking to power my Pi with a LiPo cell, so forgive me if this is not directly a Pi question. For testing, I want to safely discharge a 1200mAh cell to about 50%. If my calculations are correct, I can safely hook up the cell to a 10 ohm/10 Watt wire-wound resistor, which should put a roughly 370...
by Douglas6
Mon Oct 07, 2013 12:50 pm
Forum: Graphics, sound and multimedia
Topic: Pianobar & LIRC
Replies: 6
Views: 1740

Re: Pianobar & LIRC

I haven't tried this, but I believe you are correct: mkfifo, and then you can echo the pianobar characters to it using irexec and a lircrc config file. Check the docs for lircrc on the official LIRC website.
by Douglas6
Tue Oct 01, 2013 5:00 pm
Forum: General discussion
Topic: How to tell if model A or B
Replies: 10
Views: 8314

Re: How to tell if model A or B

[Edit: As AndrewS points out, this gives the revision, not the model. <Best Emily Littela voice> Neeeevvveeer mind!</> For what it's worth, the quick2wire python module, and the Adafruit I2C module use this: def revision(): try: with open('/proc/cpuinfo','r') as f: for line in f: if line.startswith(...
by Douglas6
Tue Oct 01, 2013 5:54 am
Forum: General discussion
Topic: COBOL Forum
Replies: 24
Views: 3677

Re: COBOL Forum

Basically anywhere where you don't want hipsters, fauxhemians and brogrammers touching your code
Now that made me smile, thank you
by Douglas6
Tue Oct 01, 2013 5:29 am
Forum: Troubleshooting
Topic: Help with understanding transistor data sheet
Replies: 10
Views: 1915

Re: Help with understanding transistor data sheet

Nicely explained guys, thanks. There oughta be a book this clear (liberal arts major)
by Douglas6
Tue Oct 01, 2013 3:30 am
Forum: Advanced users
Topic: GPIO - Circuit Monitoring
Replies: 13
Views: 6056

Re: GPIO - Circuit Monitoring

Looking forward to following along. As Gordon noted, the physical wiring alone for this project will be epic. :)
As to the programming, I'll try and help if called upon.
by Douglas6
Tue Oct 01, 2013 12:57 am
Forum: Troubleshooting
Topic: Using i2c
Replies: 9
Views: 2027

Re: Using i2c

As far as I can tell, you're ok: set all the MCP23017 port B pins as output using the IODIRB register (0x01), and then write to the OLATB register. Double and triple check your wiring against the pin outs in the datasheets. As far as I know, the MCP23017 powers up with the same config for both A and...
by Douglas6
Mon Sep 30, 2013 10:43 pm
Forum: General discussion
Topic: COBOL Forum
Replies: 24
Views: 3677

Re: COBOL Forum

Heater, glad to meetchya. COBOL paid my bills (and then some) for many years back when IBM made and sold computers. From Wall Street to LaSalle street, COBOL owned the financial systems of the Eighties. But I think to do a proper COBOL forum, we should be magnanimous and allow RPG III programmers in...
by Douglas6
Mon Sep 30, 2013 8:47 pm
Forum: General discussion
Topic: Language threads?
Replies: 24
Views: 2937

Re: Language threads?

Seems that Java is so repulsive that more people would rather program in assembler, bare metal! Or at least "other".
Or perhaps Java is so easy and intuitive, there are just no questions and no help needed :)

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