Wikipedia:Reference desk/Archives/Computing/2016 July 18

= July 18 =

Another Arduino Problem, kindly help
It has just two or three, or may be one more grounded terminal (for negative D.C. output) but several positive terminals, so many that they need numbers to be told apart. But the project I'm working on needs only one positive output (for a certain anode in the project) and lots of, literally dozens of negatives, for cathodes that had to be fed negative DC. Of course, I can't feed all the cathodes from a single Arduino source, since the whole meaning of using the programmable micro-controller is to provide different cathodes at different times. Any solution, please ? 203.134.197.96 (talk) 00:28, 18 July 2016 (UTC)
 * you tie the anode to Vcc and each of the cathodes (is this a common-anode 7-segment?) to an I/O pin (through a series resistor.) Then pull the pin low to light the segment and high to make it go out. Asmrulz (talk) 08:17, 18 July 2016 (UTC)
 * you can use a single current-limiting resistor at the anode if you make sure only one segment is lit at any instant (multiplexing.) Asmrulz (talk) 08:19, 18 July 2016 (UTC)
 * The OP might also want to consider an open-collector inverter (such as a 7406) between the Arduino output and the load - driving the LEDs (assuming that's what the load is) directly off the outputs may not work if the outputs can't sink enough current. There are dedicated 7-segment display drivers (such as the 7447) that the OP might want to consider as well. Tevildo (talk) 18:56, 18 July 2016 (UTC)
 * There are many approaches. The general concepts you need to wrap your head around here is current source and current sink. This might also be a perfect opportunity to use and learn about transistors. You can buy a handful of little BC338 for literally a few bucks and learn how to use them to source or sink current. Vespine (talk) 00:35, 19 July 2016 (UTC)

On some pages about Head Mounted Displays, you see a list of games suported by some brand of HMD, what does this mean?
On some pages about Head Mounted Displays, you see a list of games suported by some brand of HMD, what does this mean? Can't we just open a game while using HMD?201.79.79.49 (talk) 01:36, 18 July 2016 (UTC)


 * Assuming the general technology hasn't changed much... I used to work on device drivers for an HMD. I also made sure that the HMD worked with whatever version of Doom was released at the time to show it as a compatible game. While you can display the video of any game inside the helmet, translating the movement of the helmet to controls inside the game is not always seamless. So, it is probable that the list of supported games are those that work as expected. Other games might not work as expected. For example, you turn you head, but it doesn't register as a turn in the game. 209.149.113.4 (talk) 12:06, 18 July 2016 (UTC)
 * While you can display the video of any game inside the helmet,  I own a HTC Vive and you can't just display the video of any game inside the HMD, there isn't a native "mirror monitor mode". To mirror your desktop into the HMD you need to buy some extra software. I've bought it and it's cheap but personally I think it's a but of an oversight that there isn't a native mode that supports monitor mirroring. Vespine (talk) 00:16, 19 July 2016 (UTC)

Artifacts of apps
Does installing and uninstalling apps on a smartphone affect the phone's memory? In other words, when an app is uninstalled, does the available memory go back to what it was before it was installed (assuming no other changes, of course)? Or are little artifacts of the app left in the memory permanently, like little bits of debris? → Michael J Ⓣ Ⓒ Ⓜ 14:42, 18 July 2016 (UTC)
 * It probably depends on OS. Ruslik_ Zero 20:35, 18 July 2016 (UTC)
 * And obviously depends on the app. If you are talking strictly about the "app" it self, then theoretically the app "model" is supposed to keep the app like a "self contained" little bubble. The app is not supposed to "interfere" with other parts of the phone except through APIs. Removing the APP should be quite clean, (cleaner than a PC anyway). However any application CAN write things to your storage, for example a camera app can save photos to your photo roll. Those photos might remain after you delete the camera app, that's just an example, there's all sorts of data an app can write out which you might not be able to guarantee is removed when you delete the app. Vespine (talk) 00:12, 19 July 2016 (UTC)
 * Aha! Thank you. So that explains why when you go to the delete screen there are two buttons, "Clear Data" and "Delete App". (For the record, I always clear the data before deleting.) Thanks again.  → Michael J Ⓣ Ⓒ Ⓜ 12:13, 21 July 2016 (UTC)
 * In case there's some confusion, "clear data" simply clears the data that has been stored via the standard APIs for storing data. It's somewhat similar to do a clean install of an app on a PC except that as Vespine mentioned, cleaning install an app on a PC is complicated since uninstall an app may leave more data than you want. "Delete app" will "clear data" and also uninstall the app. Neither of these will remove any extra data the app has stored elsewhere by accessing the storage since the OS doesn't really monitor these properly. Also as a minor clarification to Vespine's point, if we're talking about Android while any app can access the storage, it does need permission. So if your app didn't require permission to access storage, then it shouldn't have been able to store content elsewhere. (If we're talking about iOS, while I haven't paid much attention since iOS6 I'm pretty sure apps still have very limited ability to store data outside where the OS places it unless the device is jailbroken.) Nil Einne (talk) 18:08, 22 July 2016 (UTC)

Availability of security updates for Windows 7
Has Microsoft stated for how long security updates will continue to be available for Windows 7? Thanks. --134.242.92.97 (talk) 22:55, 18 July 2016 (UTC)


 * A Web search for your question gives this page as the first result. --71.110.8.102 (talk) 03:44, 19 July 2016 (UTC)