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by PiGraham
Tue Jul 16, 2013 2:20 pm
Forum: C/C++
Topic: pThreads and globals var's
Replies: 9
Views: 1055

Re: pThreads and globals var's

thanks PiGrapham, the thread is set running by a threat_create (etc) along with thread_join at the end. Static should not mean the contents can not be changed i think it limits scope. Const does that. The program does a lot more I was just giving a little example. I tried the static as it didn't wo...
by PiGraham
Tue Jul 16, 2013 1:28 pm
Forum: C/C++
Topic: pThreads and globals var's
Replies: 9
Views: 1055

Re: pThreads and globals var's

Ignore this bit, heat induced idiocy :oops: You declared input as static, but it changes. That might have something to do with it. You can declare variables volatile to tell the compiler to always read the current value. A compiler can optimise by putting a variable into a register for some sections...
by PiGraham
Tue Jul 16, 2013 1:21 pm
Forum: Other projects
Topic: How to wifi communicate between RPis
Replies: 18
Views: 15055

Re: How to wifi communicate between RPis

Does that require both being connected to the internet? Both have to be network connected, obviously. That could be the same WiFi router/AP, with or without WAN connection. Alternatively you can configure one Pi to act as an access point that the other connects to. Or it could be over the internet ...
by PiGraham
Tue Jul 16, 2013 11:25 am
Forum: Camera board
Topic: Banding on video but not on Stills
Replies: 9
Views: 1451

Re: Banding on video but not on Stills

My camera hasn't yet arrived (tomorrow? Tuesday?) but what you describe sounds suspiciously like Mains ripple - twice in the mains cycle the 5v is dipping, and that will occur at the same place in the camera frame. So, yes, it could be power You are correct! After determining that there is no way t...
by PiGraham
Tue Jul 16, 2013 10:52 am
Forum: Recommended peripherals
Topic: Voltmeter Recommendations
Replies: 11
Views: 1924

Re: Voltmeter Recommendations

I have an Avometer. It's a bakelite fronted work of art with a really nice scale, but I don't use it. Maybe I should dig it out and put it to work again.
by PiGraham
Tue Jul 16, 2013 10:17 am
Forum: User groups and events
Topic: Portsmouth Jam 27th July?
Replies: 37
Views: 9629

Re: Portsmouth Jam 27th July?

Free tickets for Portsmouth Jam here
http://portsmouthraspberryjam-eorg.eventbrite.com/
by PiGraham
Tue Jul 16, 2013 8:45 am
Forum: Automation, sensing and robotics
Topic: Using a Pi as a Photo Finish Camera
Replies: 17
Views: 5250

Re: Using a Pi as a Photo Finish Camera

You could use IR gate sensors like these to detect when the finish line is crossed. It will be no use for precise timing, but it should do for a video replay of free-running video of the finish. Relay output is easy to connect to the GPIO. I got a couple of these and tried them out triggering my DSL...
by PiGraham
Tue Jul 16, 2013 6:51 am
Forum: Recommended peripherals
Topic: Voltmeter Recommendations
Replies: 11
Views: 1924

Re: Voltmeter Recommendations

Fluke are good, but perhaps over the top for a first meter. They start at £100. What's your budget? There are lots of perfectly adequate cheap multimeter around. Here's one that does a lot for not much dosh (£25): http://uk.farnell.com/tenma/72-7725/multimeter-digital-hand-held-1999/dp/7430582 No pa...
by PiGraham
Tue Jul 16, 2013 6:18 am
Forum: Automation, sensing and robotics
Topic: GPIO input
Replies: 8
Views: 1177

Re: GPIO input

[quote="roboenthus"Amazing! Does that mean when I am going to to sent a '1' to a GPIO pin, I can either use two resistors to divide voltage from 5v or just link the 3.3v VCC to the pin? And it also seems that any outside input and be understand as linking the VCC directly to the signal pin, Is that ...
by PiGraham
Tue Jul 16, 2013 6:00 am
Forum: Python
Topic: Controlling a stepper motor Raspberry Pi Python
Replies: 2
Views: 3154

Re: Controlling a stepper motor Raspberry Pi Python

You want a function that is called regularly, on a timer, that keeps track of a position variable and receives a 'set-point' value. Each time interval this function will compare the set-point (sp) to the current position (cp). If sp-cp >0 step forward 1 if sp-cp <0 step back 1 Now, when you change t...
by PiGraham
Mon Jul 15, 2013 5:03 pm
Forum: Camera board
Topic: Any pictures (maybe even movie) taken with the new camera?
Replies: 4
Views: 883

Re: Any pictures (maybe even movie) taken with the new camer

Search and you will find.

Some here http://www.flickr.com/groups/1884120@N23/

http://www.raspberrypi.org/archives/4290

http://www.raspberrypi.org/archives/4279

Google

There are lots more photos of Pi Cam than by Pi Cam, but look around, they are out there.
by PiGraham
Mon Jul 15, 2013 4:30 pm
Forum: Graphics, sound and multimedia
Topic: Will this monitor work well for gaming?
Replies: 3
Views: 548

Re: Will this monitor work well for gaming?

I have a very similar device and it works perfectly well with the Pi. It is too small to read console text, but you can just about guess what it says. It's a video monitor, so it runs at video rate, fine for games you might play on a Pi. Your problem, if any, will be making out details on a small lo...
by PiGraham
Mon Jul 15, 2013 12:27 pm
Forum: Camera board
Topic: Farnell Still using inadequate packaging
Replies: 6
Views: 1079

Re: Farnell Still using inadequate packaging

I had the same thing - creased cable.
by PiGraham
Mon Jul 15, 2013 11:35 am
Forum: Automation, sensing and robotics
Topic: Avoiding using Voltage Divider
Replies: 29
Views: 8750

Re: Avoiding using Voltage Divider

a series resistor limits the current that will flow through the "upper" protection diode into the 3V3 supply, thereby protecting the transistors in the GPIO for voltages higher than what they are rated for, or negative voltages. The "upped diode" being the one who's cathode is connected to 3V3, (VC...
by PiGraham
Mon Jul 15, 2013 8:49 am
Forum: Beginners
Topic: Use RPi.GPIO without root
Replies: 6
Views: 6032

Re: Use RPi.GPIO without root

PIGPIO is a 'c' library that includes a daemon that you can communicate over a pipe. I haven't tried it in this mode, but I think you should be able to use the gpio without root by setting the daemon (pigpiod) to run at boot and sending IO commands to it over a pipe or network socket. You should be...
by PiGraham
Sun Jul 14, 2013 7:26 pm
Forum: Camera board
Topic: Banding on video but not on Stills
Replies: 9
Views: 1451

Re: Banding on video but not on Stills

Do the bands move?
by PiGraham
Sat Jul 13, 2013 5:07 pm
Forum: C/C++
Topic: Coin Toss Simulator
Replies: 17
Views: 2543

Re: Coin Toss Simulator

As for PiGraham's hardware rng, I don't understand what it is saying at all! It was just something Google threw up. The idea is to use electronic noise as the source of randomness. To use it with a Pi you could sample the output once for each bit of a random number. If you want a 32 bit random numb...
by PiGraham
Sat Jul 13, 2013 11:45 am
Forum: General discussion
Topic: Camera boards back in stock at element14
Replies: 27
Views: 2069

Re: Camera boards back in stock at element14

Picam_sm.jpg
Picam_sm.jpg (56.51 KiB) Viewed 1467 times
Woohoo, delivery!
Nice new boxes too.
by PiGraham
Sat Jul 13, 2013 11:08 am
Forum: Add-ons
Topic: Remove solder from within Humble Pi holes
Replies: 12
Views: 2088

Re: Remove solder from within Humble Pi holes

... a 0.5mm drill bit and a pin vice... The trouble with that is that you risk destroying the through-hole plating. If it's only double-sided, and what you're putting in the hole can be soldered both sides, then you're alright, but if there are layers in the middle that should also be connected, yo...
by PiGraham
Sat Jul 13, 2013 7:32 am
Forum: Add-ons
Topic: SD card sticking out ? Use RSMMC
Replies: 56
Views: 24932

Re: SD card sticking out ? Use RSMMC

podly wrote:
wolfgangmob wrote:Another option is a combo adapter for micro SD to SD/USB then just cut off the USB side of the adapter.
What do you mean? Any links to this kind adapter?

cheers,
http://rolandsoft.blogspot.co.uk/2012/1 ... crosd.html
by PiGraham
Fri Jul 12, 2013 11:14 am
Forum: Beginners
Topic: Can Raspberry Pi do this?
Replies: 8
Views: 1383

Re: Can Raspberry Pi do this?

Thanks Mahjong.
by PiGraham
Fri Jul 12, 2013 10:07 am
Forum: Beginners
Topic: Can Raspberry Pi do this?
Replies: 8
Views: 1383

Re: Can Raspberry Pi do this?

Did i read somewhere that the pi has full OTG USB hardware? It may one day work as a USB slave memory device, like a smart phone.
Probably requires clever low level code to do that though.
by PiGraham
Fri Jul 12, 2013 9:28 am
Forum: General discussion
Topic: Camera lucida
Replies: 2
Views: 487

Re: Camera lucida

There are pico projectors for a little under a hundred GBP, even as cheap as 45 (don't expect good image quality for that) That would be compact and simple to implement. If you don't mind bulk you could arrange an inclined sheet of glass so that it reflects your monitor, so that looking from above y...

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