This question has been redirected from raspberry pi community. Some of the questions have been answered by @Milliways, so those questions have been edited out.  I'm using this Raspberry Pi High-Precision AD/DA Expansion Board from waveshare. I have some questions regarding its ADC (model name: ADS1256) unable to give out negative value. Specifically, only giving out negative values around -0.1V. Here are details of my problem.  Current situation:   Using the user manual provided with the board, I have managed to read analog input data from on-board potentiometer and LDR (converted to digital data) using their sample code. In order to use the on-board potentiometer and LDR, I've connected jumpers to the appropriate positions as metioned in the manual.  Now, I've connected a function generator, sending out +/-2V amplitude of analog sine wave signal, to the waveshare ADC board. By modifying the sample code provided, I've printed out the converted data and ploted them, which is the figure shown below (y-axis = voltage, x-axis = number of data)      figure 1: sine wave plot   Here are the questions:  1. Is this normal phenomenon for this ADC board?  2. If so, am I correct to assume that this ADC can only receive analog inputs above zero? (I've looked through the ADS1256 datasheet and studied a bit, but had hard time understanding the input range found in the document, shown below.)  3. If above assumption is true, then can the analog input range be changed?   I've been told (As @Milliways had suggested) that there are established techniques to offset input DC. To elaborate, I need to change the input range of the ADC from 0 to 5V to -2.5V to +2.5V.  Can this be done by changing ADC registers or do I need a separate circuit like op amp?       figure 2: datasheet screenshots, page 2 and page 3     Product page:   Manual :   Sample code :   ADC datasheet :
I have a front end module that generates an (ECG) signal that varies from +/-2.5 V. I want to shift this signal to 0 - 5V. What is the best way to do this? Would a summing amplifier like the below circuit good enough? With R1 = R2 and V1 = 2.5V, V2 = my signal, V3 = V4 = GND
Why does LuaTeX plus breqn quadruple output of \text{} when in display-math mode? MWE needs to be compiled with LuaTeX to reproduce the problem:  \documentclass[11pt]{report}% \usepackage{amsmath,mathtools} \usepackage{breqn}                          \begin{document} $J^{\ast} = \text{JFK} \to \text{NO} \to \text{SFO}$ \[ J^{\ast} = \text{JFK} \to \text{NO} \to \text{SFO} \] \end{document}   Gives (no compile error or any warning) the following strange output    I have to use breqn package. If I remove it, then I get the expected output    Is there a way to work around this, so I can use breqn and get correct output?  TL 2015. filelist: (compiled with lualatex)  This is LuaTeX, Version beta-0.80.0.1 (TeX Live 2015) (rev 5863)   *File List*   report.cls    2014/09/29 v1.4h Standard LaTeX document class   size11.clo    2014/09/29 v1.4h Standard LaTeX file (size option)  amsmath.sty    2013/01/14 v2.14 AMS math features  amstext.sty    2000/06/29 v2.01   amsgen.sty    1999/11/30 v2.0   amsbsy.sty    1999/11/29 v1.2d   amsopn.sty    1999/12/14 v2.01 operator names mathtools.sty    2015/11/12 v1.18 mathematical typesetting tools   keyval.sty    2014/10/28 v1.15 key=value parser (DPC)     calc.sty    2014/10/28 v4.3 Infix arithmetic (KKT,FJ)  mhsetup.sty    2010/01/21 v1.2a programming setup (MH)    breqn.sty    2015/08/11 v0.98d Breaking equations    expl3.sty    2015/12/20 v6326 L3 programming layer (loader)  expl3-code.tex    2015/12/20 v6326 L3 programming layer  l3pdfmode.def    2015/11/11 v6250 L3 Experimental driver: PDF mode flexisym.sty    2015/08/11 v0.98d Make math characters macros   cmbase.sym    2007/12/19 v0.92 mathstyle.sty    2015/08/11 v0.98d Tracking mathstyle implicitly graphicx.sty    2014/10/28 v1.0g Enhanced LaTeX Graphics (DPC,SPQR) graphics.sty    2014/10/28 v1.0p Standard LaTeX Graphics (DPC,SPQR)     trig.sty    1999/03/16 v1.09 sin cos tan (DPC) graphics.cfg    2010/04/23 v1.9 graphics configuration of TeX Live   pdftex.def    2011/05/27 v0.06d Graphics/color for pdfTeX infwarerr.sty    2010/04/08 v1.3 Providing info/warning/error messages (HO)  ltxcmds.sty    2011/11/09 v1.22 LaTeX kernel commands for general use (HO) supp-pdf.mkii pdftexcmds.sty    2011/11/29 v0.20 Utility functions of pdfTeX for LuaTeX (HO) ifluatex.sty    2010/03/01 v1.3 Provides the ifluatex switch (HO)    ifpdf.sty    2011/01/30 v2.3 Provides the ifpdf switch (HO) luatex-loader.sty    2010/03/09 v0.4 Lua module loader (HO) epstopdf-base.sty    2010/02/09 v2.5 Base part for package epstopdf   grfext.sty    2010/08/19 v1.1 Manage graphics extensions (HO) kvdefinekeys.sty    2011/04/07 v1.3 Define keys (HO) kvoptions.sty    2011/06/30 v3.11 Key value format for package options (HO) kvsetkeys.sty    2012/04/25 v1.16 Key value parser (HO) etexcmds.sty    2011/02/16 v1.5 Avoid name clashes with e-TeX commands (HO) epstopdf-sys.cfg    2010/07/13 v1.3 Configuration of (r)epstopdf for TeX Live  ***********   Update  I found another case of duplication when using breqn, which does not involve \text at all. But the solution provided below also fixes this issue. I am adding this second case here for reference just in case it might be useful. Here is MWE  \documentclass[11pt]{article} \usepackage[T1]{fontenc} \usepackage{amsmath,mathtools} \usepackage{breqn} \begin{document} \[ \underset{\mathbf{S}} {\operatorname{arg\,min}}      \sum_{i=1}^{k} \sum_{\mathbf x \in S_i}       \left\| \mathbf x - \boldsymbol\mu_i \right\|^2  \] \end{document}   The output is    After adding the patch in the answer below the correct output is now given, which is Remove rogue app from menu bar I have a rogue item on my menu bar from a terrible piece of printer/scanner software. I long ago removed the app, but the button for the app remains in the menu bar.   Is there any central way for me to remove an item from the menu bar? Any plist I can hack? command line trick, etc?  It's the one to the left of the Facebook icon:    (I tried holding Command and dragging it away, but it doesn't seem to respect that convention.) I am using natbib and agsm for harvard-style referencing. My related code is  \usepackage{natbib} \bibliographystyle{agsm}   Then I am using \citep{} for citations. My problem is that in text I am getting     (Author et al. 2012)   but and I want     (Author et al. 2012)   Does anyone know how to change this and get 'et al' in italics in the text?  I am using TexPad and BibDesk and I have not been able to find the .bst files in Terminal.  I know that it is often correct to have the 'et al.' unitalicised but my university regulations requires italics. I would like to protect myself from unreasonable demands during my work day.  One of those is telling people that I will not respond to any emails before 3pm.  I'd like to set up a rule in outlook that replies to all emails before 3pm with a specific message. I'd like this to be done every day, no matter the date.  How do I set this up?  I've scoured Google best I can so far, and I think, based on a Exchange forum, that a script might be needed for this.  But what I found so far was only server side scripts. I need something on my own machine.  references: How to recover files from dead windows using dos? I am trying to find the correct opposite of a delegate in the context of a person being a representative of someone else that have allowed or chosen them to be their delegate. What would you call that "someone else?" The only word I could find is a delegator (which isn't a real word in English) or assigner, but they are technical words rather than descriptive.    Any other word I could use?    Think of it in a sentence like this:       Here is a list of all the delegates in the company.   But that is the list of their _ _ _ _ _ (what can go here?).   I am trying to avoid fillers such as:  bosses, agents, managers, etc. Canadian visa rules for flight connections I know that in the US foreigners must have a US visa if they have a connection in the US, even if they fly from a different country to a different country. That is because in the US you have to go through passport control regardless of your final destination.  What is the situation in Canada? Does a person who would need a visa to enter Canada need a visa to connect through Canada without exiting the airport? Why are Perl 5's function prototypes bad? Wilson and Fermat's Theorem Proof of one inequality $a+b+c\leq\frac{a^3}{bc}+\frac{b^3}{ca}+\frac{c^3}{ab}$ How to prove this for positive real numbers? $$a+b+c\leq\frac{a^3}{bc}+\frac{b^3}{ca}+\frac{c^3}{ab}$$  I tried AM-GM, CS inequality but all failed. So this is something I just found out about that I find odd:   Opportunity attacks—trigger off of movement that uses the creatures movement (action, move action, bonus action, reaction.)  Sentinel—Whenever a creature within 5 ft of you makes an attack at a creature other than you.   Booming blade—If the target willingly moves.   Mental Prison spell—if it moves, attacks through it, or reaches any part of body out of it.   So the “willingly” is different than other rulings for how effects related to movement works. However what exactly fits willing?   Cause fear—nope magic is having them move. Dissonant whispers—same thing. They have to immediately move.   So the creature has to want to move completely of its own accord.   Crown of Madness—Humanoid creature you choose must make a wisdom saving throw. On a fail it is charmed by you. (Next is flavor text so skipping.) While charmed in this way the target must make an attack on a creature other than itself that you mentally choose on each of its turns before moving.  It can act normally if you choose no creature or if none are within reach.   Crown of madness isn't making them move but doesnt specifically say willing.  And if the ruling for willing is movement not caused by magic what about magic causing situations where you take damage if you don't move. Would a creature shimmering with evocation energy be spared because he moved out of the magical blender that is cloud of daggers? If no, then what is the go-to rule for willing movement that I should be using?  In short, what movement counts as willing, and where can it be found? Is moving out of obvious danger caused by magic, willing? Is moving away from an ally so you don't hit them, willing?   If there isn't any actual ruling on willing, that's fine; I'll go back to running it with my interpretation, so that it has same wording as AOO. If there is an actual 5e term or explanation for willing (that isn't Sage Advice), please let me know. I just don't see why it was necessary to put a term in the spell that isn't used anywhere else. I understand it could have been overlooked since it was in a splatbook or has just been ignored since most people probably assume that there is "Forced " and "Willing" movement, with the willing being defined as: any movement from an action, move action, bonus action, or reaction. In same way AOO work. How is Dru-Zod/General Zod still alive after this character died? Securing SSH server against bruteforcing I have a little SVN server, old dell optiplex running debian. I don't have that high demands on my server, because its just a little SVN server... but do want it to be secure.  I just renewed my server to a newer and better optiplex, and started looking a bit into the old server. I took it down after experiencing problems. When I check the logs, its full of brute-force attempts and somehow someone has succeeded to enter my machine. This person created some extra volume called "knarkgosse" with two dirs "root" and "swap1" or something.  Don't really know why and what they do, but sure do want to prevent this from happening again. I find this a bit strange though because I change my password ever few months or so, and the passwords are always random letters and numbers put together... not easy to brute-force.  I know I can prevent root from logging in, and use sudoers... and change the SSH port, but what more can I do?  So I have a few questions:   How can I prevent logging in for 5 minutes after X amount of incorrect tries. Or slow tries down after each incorrect try? Is there some kind of central blacklist which a server can connect to? A blacklist that keeps track of IP addresses that are "unsafe" and should never be granted access? What more can I do to apply safety to my server?   Like I said earlier, I am running Debian 5 with Apache (www-data user problem?), svn, mysql, php, phpmyadmin, hudson. It is on a home network with port forwarding on 80, 443, 8080, 8180, 23 and 22. Proving this identity $\sum_k\frac{1}{k}\binom{2k-2}{k-1}\binom{2n-2k+1}{n-k}=\binom{2n}{n-1}$ using lattice paths Need help understanding "getbits()" method in Chapter 2 of K&R C In chapter 2, the section on bitwise operators (section 2.9), I'm having trouble understanding how one of the sample methods works.  Here's the method provided:  unsigned int getbits(unsigned int x, int p, int n) {     return (x &gt;&gt; (p + 1 - n)) &amp; ~(~0 &lt;&lt; n); }   The idea is that, for the given number x, it will return the n bits starting at position p, counting from the right (with the farthest right bit being position 0). Given the following main() method:  int main(void) {     int x = 0xF994, p = 4, n = 3;     int z = getbits(x, p, n);     printf("getbits(%u (%x), %d, %d) = %u (%X)\n", x, x, p, n, z, z);      return 0; }   The output is:     getbits(63892 (f994), 4, 3) = 5 (5)   I get portions of this, but am having trouble with the "big picture," mostly because of the bits (no pun intended) that I don't understand.  The part I'm specifically having issues with is the complements piece: ~(~0 &lt;&lt; n). I think I get the first part, dealing with x; it's this part (and then the mask) that I'm struggling with -- and how it all comes together to actually retrieve those bits. (Which I've verified it is doing, both with code and checking my results using calc.exe -- thank God it has a binary view!)  Any help? I upgraded to Chrome 61.0.3163 via ppa on Ubuntu 16.04 but it won't launch because NSS out of date. Launching Chrome in terminal gives:  NSS &gt;= 3.26 is required. Please upgrade to the latest NSS, and if you still get this error, contact your distribution maintainer.   Running   sudo apt-get install libnss3   gives  libnss3 is already the newest version (2:3.21-1ubuntu4)   Should I try to get a newer version of libnss that's not in the repository? I downgraded my version of Chrome for now.  Edit:  apt-cache policy libnss3 libnss3:   Installed: 2:3.21-1ubuntu4   Candidate: 2:3.21-1ubuntu4   Version table:  *** 2:3.21-1ubuntu4 500         500 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 Packages         100 /var/lib/dpkg/status  cat /etc/apt/sources.list # deb cdrom:[Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)]/ xenial main restricted  # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://us.archive.ubuntu.com/ubuntu/ xenial main restricted # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial main restricted  ## Major bug fix updates produced after the final release of the ## distribution. # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-updates main restricted  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team, and may not be under a free licence. Please satisfy yourself as to ## your rights to use the software. Also, please note that software in ## universe WILL NOT receive any review or updates from the Ubuntu security ## team. deb http://us.archive.ubuntu.com/ubuntu/ xenial universe # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial universe # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-updates universe  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu  ## team, and may not be under a free licence. Please satisfy yourself as to  ## your rights to use the software. Also, please note that software in  ## multiverse WILL NOT receive any review or updates from the Ubuntu ## security team. deb http://us.archive.ubuntu.com/ubuntu/ xenial multiverse # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial multiverse # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-updates multiverse  ## N.B. software from this repository may not have been tested as ## extensively as that contained in the main release, although it includes ## newer versions of some applications which may provide useful features. ## Also, please note that software in backports WILL NOT receive any review ## or updates from the Ubuntu security team. # deb-src http://us.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse  ## Uncomment the following two lines to add software from Canonical's ## 'partner' repository. ## This software is not part of Ubuntu, but is offered by Canonical and the ## respective vendors as a service to Ubuntu users. deb http://archive.canonical.com/ubuntu xenial partner deb-src http://archive.canonical.com/ubuntu xenial partner  # deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted # deb-src http://security.ubuntu.com/ubuntu xenial-security universe # deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse Destructive interference and energy conservation In case of interference, we know, energy is neither destroyed, nor created; but only redistributed. But in the case of an extremely thin film, due to a reflection and hence a phase difference of $\pi$, the film always appears dark due to destructive interference. So, where does the energy go? Please help me to find elements $a,b$ in a ring $R$ such that $a\mid b$ and $b\mid a$, but there does not exist any unit $u$ in $R$ such that $a=ub$. I am currently using 19.04 and I got "No new release found for 19.10" If I have a Type C visa from the Norwegian embassy valid for February 9-28, and my Type D national visa from the German embassy valid from March 1 - August 31, 2017, do I need to leave/fly out of the Schengen area on the 28th and fly back on the 1st day of March?