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by Hoagie
Sun Nov 05, 2017 8:47 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 38kHz modulation with GPIO output??
Replies: 6
Views: 2781

Re: 38kHz modulation with GPIO output??

i’ll probably regret trying to post this from an ipad, but here goes. /* gcc -o play playcode.c */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <errno.h> #include <stdarg.h> #include <stdint.h> #include <signal.h> #include <time.h> #include <sys/time.h> #in...
by Hoagie
Sat Oct 14, 2017 9:05 pm
Forum: Automation, sensing and robotics
Topic: Buffered Sound Detector
Replies: 3
Views: 335

Re: Buffered Sound Detector

apparently wiringPi does interrupt based GPIO. check this page out
http://wiringpi.com/reference/priority- ... d-threads/
It looks like you will be able to setup an interrupt to trigger when the pin changes state, even for,an extremely short time.
by Hoagie
Thu Oct 12, 2017 6:48 pm
Forum: Automation, sensing and robotics
Topic: 2 x RS232 in -> 1 x RS232 out + web interface
Replies: 2
Views: 369

Re: 2 x RS232 in -> 1 x RS232 out + web interface

Though the Pi does have multiple RS232 capability, one is done in software and isn't very good. Also, if the RS232 input on the lighting system is standard RS232 voltage, you'll need adaptors. It may be best to just get three USB to RS232 adaptors so you can use two for the inputs and one for the ou...
by Hoagie
Tue Oct 03, 2017 8:58 pm
Forum: Automation, sensing and robotics
Topic: Mario "?"-box punch sensor
Replies: 1
Views: 318

Re: Mario "?"-box punch sensor

It sounds simple enough. The one thing that may catch you out is the time the switches make contact for. It could be pretty short, so you'll need quite a high sampling rate. Personally, I'd go for the vibration sensor and probably just keep reading the GPIO pins as quickly as possible while it's not...
by Hoagie
Tue Oct 03, 2017 8:44 pm
Forum: Automation, sensing and robotics
Topic: Halloween, pir sensor, scary video
Replies: 13
Views: 1187

Re: Halloween, pir sensor, scary video

I'm don't really know python but here's my best guess. Change this line in the second file scareFile = "3secondScare.mp4" to something like this scareFile = ["3secondScare1.mp4","3secondScare2.mp4","3secondScare3.mp4","3secondScare4.mp4","3secondScare5.mp4"] Where the filenames are the names of your...
by Hoagie
Tue Oct 03, 2017 8:29 pm
Forum: Automation, sensing and robotics
Topic: IoT best gui interface option
Replies: 5
Views: 532

Re: IoT best gui interface option

For things like this, I prefer a HTML interface. Mainly because you effectively get a mobile app for free.
by Hoagie
Sun Sep 24, 2017 9:38 am
Forum: Automation, sensing and robotics
Topic: 433 MHz rx stops working when tx is connected
Replies: 1
Views: 273

Re: 433 MHz rx stops working when tx is connected

Are you sure you have the transmitter off when it should be idle? If the Pi is outputting the signal to transmit, the transmitter is likely to be swamping the receiver and blocking the signal. It could be that the transmitter expects an inverted signal where a 0 means transmit and a 1 means don't tr...
by Hoagie
Sun Sep 24, 2017 9:31 am
Forum: Automation, sensing and robotics
Topic: Laser dust sensor
Replies: 6
Views: 506

Re: Laser dust sensor

I'm not a python person, but something like a loop through the data where a variable (x for instance) is the index. If the data at x t x is 42 and the data at (x+1) is 4d (there must be some notation for hex in python) then you know the start of the data. You can read the values you need by adding t...
by Hoagie
Fri Sep 22, 2017 7:17 pm
Forum: Automation, sensing and robotics
Topic: Solution for water pump control, RPi suitable?
Replies: 7
Views: 837

Re: Solution for water pump control, RPi suitable?

You don't mention much about the pressure sensors, but as you mention you have a monitor on the Pi, I guess you have that covered anyway. Look on eBay for ADC modules to do the analogue outputs. I'm sure there will be something that can give 0-5V. As mentioned earlier, the Pi isn't really intended f...
by Hoagie
Fri Sep 22, 2017 6:59 pm
Forum: Automation, sensing and robotics
Topic: Need a solution for Tracking Main Power Availability Status
Replies: 5
Views: 431

Re: Need a solution for Tracking Main Power Availability Status

As someone pointed out, you'd be best using a relay That makes sure you don't give dangerous voltages to the Pi GPIO pins. Using the wiringPi library makes it easy to set a GPIO pin to an input with a pullup. Connect the relay contacts between this pin and Gnd. The software could detect the pin stat...
by Hoagie
Fri Sep 22, 2017 6:48 pm
Forum: Automation, sensing and robotics
Topic: Laser dust sensor
Replies: 6
Views: 506

Re: Laser dust sensor

If it just pumps the packets out continuously, you could read twice the length and then throw out all the data up to the 424d. The remainder will be at least one full reading.
by Hoagie
Fri Sep 22, 2017 6:29 pm
Forum: Automation, sensing and robotics
Topic: My crazy quadcopter / Pi Drone experiment
Replies: 7
Views: 653

Re: My crazy quadcopter / Pi Drone experiment

Hi, I've played with the HC-SR04 module. it runs from 5V, but the trigger input works fine on the 3.3 from the Pi. The sensor output can be translated to 3.3 with a simple potential divider. They "see" in a cone 15 degrees wide and their distance sensitivity depends on the object they're pointed at....
by Hoagie
Sat Sep 16, 2017 5:42 pm
Forum: Automation, sensing and robotics
Topic: how to set up multitasking
Replies: 18
Views: 1104

Re: how to set up multitasking

I skip read the last few posts after reading that it wouldn't shut down anymore. This sounds like you have left the other thread running. I don't know how you can send values between threads in Python, but if your main one can set a flag in the background thread it can use this flag to exit its own ...
by Hoagie
Sun Dec 18, 2016 6:13 pm
Forum: Other projects
Topic: Festive wallboard
Replies: 0
Views: 243

Festive wallboard

Hi, In my office we have a build monitor running on a big TV so we can all see whether our software is broken. It's just running a full screen browser pointing to an internal web server. We decided to make it a bit festive and after many iterations came up with the html and images in the attached zi...
by Hoagie
Thu Nov 03, 2016 8:23 pm
Forum: Other projects
Topic: Raspberry pi to Oculus Rift
Replies: 3
Views: 913

Re: Raspberry pi to Oculus Rift

The older Rifts had HDMI connectors. If this one has, I can't see any reason that the Pi wouldn't show something on it.
by Hoagie
Thu Nov 03, 2016 8:19 pm
Forum: Other projects
Topic: Nextion screen as input for pi?
Replies: 4
Views: 815

Re: Nextion screen as input for pi?

Can you give more information on it. A link or model number etc.
by Hoagie
Thu Nov 03, 2016 8:03 pm
Forum: Other projects
Topic: Pi Zero gadget + Wi-Fi
Replies: 3
Views: 689

Re: Pi Zero gadget + Wi-Fi

I have a Pi zero setup with a WiFi dongle acting as a hotspot. Nothing special, you just need to use a micro to full size usb adaptor. Mine came with one. The wifi is the only way in to mine, nothing elseo is connected. I just tell my laptop, phone or whatever to connect to it's hotspot and access i...
by Hoagie
Sun Oct 23, 2016 12:43 pm
Forum: Other projects
Topic: [Help][First Project] Modify/replace Electric candle melter
Replies: 2
Views: 377

Re: [Help][First Project] Modify/replace Electric candle mel

Hi, I can't think of anything that would limit the temperature for you, but maybe the Pi could sense it and control the heater. You can do all kinds of control algorithms in software and keep it much more stable than a simple on off thermostat too. Some kind of mug warmer maybe the right size. I'd t...
by Hoagie
Sun Oct 23, 2016 7:28 am
Forum: General discussion
Topic: nanosecond
Replies: 30
Views: 4106

Re: nanosecond

I know this is an old thread, but if anyone is still reading it, they may be interested to see that it is actually possible.

http://www.ceirogstudios.co.uk/sol/sol.html
by Hoagie
Sat Oct 22, 2016 6:11 pm
Forum: Other projects
Topic: The Speed of Light
Replies: 6
Views: 1005

Re: The Speed of Light

You might find this interesting http://codeandlife.com/2012/07/03/benchmarking-raspberry-pi-gpio-speed/ though not up to date and doesn't include pigpio http://abyz.co.uk/rpi/pigpio/index.html you might find piscope shows you some things too. Also not that the R^2 value is pretty much zero, that if...
by Hoagie
Sat Oct 22, 2016 5:51 pm
Forum: Other projects
Topic: The Speed of Light
Replies: 6
Views: 1005

Re: The Speed of Light

Burngate wrote:ok, since time goes faster at the top of a mountain than at the bottom, with that result you should be able to work out your altitude.
My estimate is that you're on top of a high mountain. Very high.
I'd expect most people wouldn't try this unless they were high.
by Hoagie
Sat Oct 22, 2016 3:54 pm
Forum: Other projects
Topic: The Speed of Light
Replies: 6
Views: 1005

The Speed of Light

Hi,

I recently decided to try and measure the speed of light directly using a Raspberry Pi. Here's a writeup of the project, including circuit diagrams and source code.
http://www.ceirogstudios.co.uk/sol/sol.html

Hope some of you find it interesting.

Thanks,
Geoff.
by Hoagie
Sat Oct 08, 2016 3:52 pm
Forum: Troubleshooting
Topic: WiFi ONLY works if Ethernet is plugged in
Replies: 45
Views: 19497

Re: WiFi ONLY works if Ethernet is plugged in

Thanks.

Putting the wlan0 section before eth0 sorted this for me too.
by Hoagie
Tue Oct 20, 2015 5:50 am
Forum: Recommended peripherals
Topic: wireless AP with hostapd and realtek chipset (works)
Replies: 40
Views: 90164

Re: wireless AP with hostapd and realtek chipset (works)

Hi,

Has anyone managed to get this working with Rasbian Jessie? I had no problem on Wheezy, but keep getting this on Jessie when starting hostapd.

Code: Select all

nl80211: Could not configure driver mode
nl80211 driver initialization failed.
hostapd_free_hapd_data: Interface wlan0 wasn't started
Thanks.
by Hoagie
Sat Jan 03, 2015 4:05 pm
Forum: Advanced users
Topic: make backup dd image while pi is live
Replies: 8
Views: 13314

Re: make backup dd image while pi is live

An interesting (well I like it) side effect of saving an image to a network location, is that you can mount it and read files from it, almost as if it was a real card plugged into the pi. It's easier to do if you only image the partitions and not the whole card, but it's still possible with a card i...

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