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  • Figuring out the Nyquist performance limitation of an ADC on an example PIC microcontroller

    - by AKE
    I'm spec-ing the suitability of a dsPIC microcontroller for an analog-to-digital application. This would be preferable to using dedicated A/D chips and a separate dedicated DSP chip. To do that, I've had to run through some computations, pulling the relevant parameters from the datasheets. I'm not sure I've got it right -- would appreciate a check! (EDITED NOTE: The PIC10F220 in the example below was selected ONLY to walk through a simple example to check that I'm interpreting Tacq, Fosc, TAD, and divisor correctly in working through this sort of Nyquist analysis. The actual chips I'm considering for the design are the dsPIC33FJ128MC804 (with 16b A/D) or dsPIC30F3014 (with 12b A/D).) A simple example: PIC10F220 is the simplest possible PIC with an ADC Runs at clock speed of 8MHz. Has an instruction cycle of 0.5us (4 clock steps per instruction) So: Taking Tacq = 6.06 us (acquisition time for ADC, assume chip temp. = 50*C) [datasheet p34] Taking Fosc = 8MHz (? clock speed) Taking divisor = 4 (4 clock steps per CPU instruction) This gives TAD = 0.5us (TAD = 1/(Fosc/divisor) ) Conversion time is 13*TAD [datasheet p31] This gives conversion time 6.5us ADC duration is then 12.56 us [? Tacq + 13*TAD] Assuming at least 2 instructions for load/store: This is another 1 us [0.5 us per instruction] Which would give max sampling rate of 73.7 ksps (1/13.56) Supposing 8 more instructions for real-time processing: This is another 4 us Thus, total ADC/handling time = 17.56us (12.56us + 1us + 4us) So expected upper sampling rate is 56.9 ksps. Nyquist frequency for this sampling rate is therefore 28 kHz. If this is right, it suggests the (theoretical) performance suitability of this chip's A/D is for signals that are bandlimited to 28 kHz. Is this a correct interpretation of the information given in the data sheet in obtaining the Nyquist performance limit? Any opinions on the noise susceptibility of ADCs in PIC / dsPIC chips would be much appreciated! AKE

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  • Using Apache Environment Variables to set custom ErrorDocument

    - by Tad
    I've got a set of RewriteCond rules that test for various mobile devices and then set environment variables like "env=device:.iphone" or "env=device:.smartphone" if the useragent matches an iPhone or Android device. I'm trying to now redirect the user to custom-styled 404/500 server error pages for each device, by way of the error pages. Ideally I'd like to be able to test for a variable being there, and then write in a custom ErrorDocument string. But an apache doesn't seem to work in this case. Any ideas how I can construct if/else tests in an apache conf file for environment vars?

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  • Figuring out the performance limitation of an ADC on a PIC microcontroller

    - by AKE
    I'm spec-ing the suitability of a microcontroller like PIC for an analog-to-digital application. This would be preferable to using external A/D chips. To do that, I've had to run through some computations, pulling the relevant parameters from the datasheets. I'm not sure I've got it right -- would appreciate a check! Here's the simplest example: PIC10F220 is the simplest possible PIC with an ADC. Runs at clock speed of 8MHz. Has an instruction cycle of 0.5us (4 clock steps per instruction) So: Taking Tacq = 6.06 us (acquisition time for ADC, assume chip temp. = 50*C) [datasheet p34] Taking Fosc = 8MHz (? clock speed) Taking divisor = 4 (4 clock steps per CPU instruction) This gives TAD = 0.5us (TAD = 1/(Fosc/divisor) ) Conversion time is 13*TAD [datasheet p31] This gives conversion time 6.5us ADC duration is then 12.56 us [? Tacq + 13*TAD] Assuming at least 2 instructions for load/store: This is another 1 us [0.5 us per instruction] Which would give max sampling rate of 73.7 ksps (1/13.56) Supposing 8 more instructions for real-time processing: This is another 4 us Thus, total ADC/handling time = 17.56us (12.56us + 1us + 4us) So expected upper sampling rate is 56.9 ksps. Nyquist frequency for this sampling rate is therefore 28 kHz. If this is right, it suggests the (theoretical) performance suitability of this chip's A/D is for signals that are bandlimited to 28 kHz. Is this a correct interpretation of the information given in the data sheet? Any pointers would be much appreciated! AKE

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  • C++ Problem: Class Promotion using derived class

    - by Michael Fitzpatrick
    I have a class for Float32 that is derived from Float32_base class Float32_base { public: // Constructors Float32_base(float x) : value(x) {}; Float32_base(void) : value(0) {}; operator float32(void) {return value;}; Float32_base operator =(float x) {value = x; return *this;}; Float32_base operator +(float x) const { return value + x;}; protected: float value; } class Float32 : public Float32_base { public: float Tad() { return value + .01; } } int main() { Float32 x, y, z; x = 1; y = 2; // WILL NOT COMPILE! z = (x + y).Tad(); // COMPILES OK z = ((Float32)(x + y)).Tad(); } The issue is that the + operator returns a Float32_base and Tad() is not in that class. But 'x' and 'y' are Float32's. Is there a way that I can get the code in the first line to compile without having to resort to a typecast like I did on the next line?

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  • Python base classes share attributes?

    - by tad
    Code in test.py: class Base(object): def __init__(self, l=[]): self.l = l def add(self, num): self.l.append(num) def remove(self, num): self.l.remove(num) class Derived(Base): def __init__(self, l=[]): super(Derived, self).__init__(l) Python shell session: Python 2.6.5 (r265:79063, Apr 1 2010, 05:22:20) [GCC 4.4.3 20100316 (prerelease)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import test >>> a = test.Derived() >>> b = test.Derived() >>> a.l [] >>> b.l [] >>> a.add(1) >>> a.l [1] >>> b.l [1] >>> c = test.Derived() >>> c.l [1] I was expecting "C++-like" behavior, in which each derived object contains its own instance of the base class. Is this still the case? Why does each object appear to share the same list instance?

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  • Memories about Tadeusz Golonka

    - by Damian
    Today at 10:55 AM, Tadeusz Golonka - my greatest  Mentor and Teacher  passed away. I had te opportunity to met Tadek in person several times last years. It was always a great experience to see how he shared his energy and passion. I was always impressed and had a lot of new ideas after such meeting or lecture. I can remember the meeting  in early 2009 and his briliant speech he did for us, the MVP community in Poland. We spent two days together and he talked to us all the time. He gave us examples how to share IT passion to other people and how to be better person for others. He was the greates Mentor I have ever met - I realized this during that meeting. My greates dream was and still is to be "like Tadek". Many Times I just went to events to see / hear him on stage ("in action"). I always wanted to have his energy, empathy and passion. Now I have to live without his good words and advices....Let me put here the words that Adam Cogan wrote on Tadek's profile on Facebook. I just can't write about that fatal accident. "The circumstances of Tadeusz Golonka death are too tragic. Tad stood up to offer his seat to an elderly lady, he lost his balance and then he slipped and hit the tram door hard. He then fell out of the tram and hit the metal barriers that separate the tram rails from the street. It was a severe accident...... So horrible.  At first it was a miracle is that he survived... he fought for several days.  My thoughts are with his lovely family. The family have asked for blood donations as a symbolic gift. Tad received a lot of blood.  Thank you Tad, you were a wonderful person. I will remember you as a kind man, a gentleman. "RIP Tadeusz- You will never ever be forgotten. You are with us all the time  

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  • Handling packet impersonating in client-server model online game

    - by TheDespite
    I am designing a server-client model game library/engine. How do I, and should I even bother to handle frequent update packet possible impersonating? In my current design anyone could copy a packet from someone else and modify it to execute any non-critical action for another client. I am currently compressing all datagrams so that adds just a tad of security. Edit: One way I thought about was to send a unique "key" to the verified client every x_time and then the client has to add that to all of it's update packets until a new key is sent. Edit2: I should have mentioned that I am not concerned about whether the actions described in the packet are available to the client at the time, this is all checked by the server which I thought was obvious. I am only concerned about someone sending packets for another client.

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  • Elegant ways to handle if(if else) else

    - by Benjol
    This is a minor niggle, but every time I have to code something like this, the repetition bothers me, but I'm not sure that any of the solutions aren't worse. if(FileExists(file)) { contents = OpenFile(file); // <-- prevents inclusion in if if(SomeTest(contents)) { DoSomething(contents); } else { DefaultAction(); } } else { DefaultAction(); } Is there a name for this kind of logic? Am I a tad too OCD? I'm open to evil code suggestions, if only for curiosity's sake...

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  • How do I calculate a SWAP partition?

    - by Dean Howell
    Since the late 90s I've always understood that it is best practice to allocate twice the amount of physical RAM as swap space. I just received my new laptop in the mail and it came with 6GB of RAM. In a separate order I had 16GB of RAM to replace the preinstalled. I didn't have the right torx driver to get to the RAM in this machine, so I installed Ubuntu and manually set a 16GB partition for swap. 32GB seemed a tad excessive... Did I make the right choice? Would my machine perform better if there was no SWAP at all?

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  • Is PluralSight worth the cost [closed]

    - by B Woods
    I am an looking at a few different supplemental learning courses to help me beef up my skills but unsure which one to use. I am interested in PluralSight because I work for the government and they use all Microsoft technologies for the most part. I like the courses on PluralSight but the price tag is pretty hefty. I am not sure how good the courses are because I cannot view the ones I want so I am a tad bit skeptical. I am sure some of you have PluralSight, do you think its a good investment for your learning or should I just stick with books/internet? Any suggestions?

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  • Handling & processing credit card payments

    - by Bob Jansen
    I'm working on program that charges customers on a pay as you go per month modal. This means that instead of the customers paying their invoices at the start of the month, they will have to pay at the end of the month. In order to secure the payments I want my customers credit card information stored so that they can be charged automatically at the end of the month. I do not have the resources, time, or risk to handle and store my customers credit card information on my servers and am looking for a third party solution. I'm a tad overwhelmed by all the different options and services that are out there and was wondering if anyone with experience have any recommendations and tips. I'm having difficulty finding services that allow me to to store my customers credit card information and charge them automatically. Most of them seem to offer an invoice styled approach.

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  • PHP error log does not display script names nor does it display the errors' line numbers [migrated]

    - by gnxtech3
    I think the title is self-explanatory, and my Google-fu isn't bringing up anything useful. I'm working on a new host, and my php error log only displays the error itself, not which script is the offender, nor which line number the error is occurring on. Makes it a tad difficult to debug, especially since there's only 1 error in the script. More info: I'm not using a custom error handler that I'm aware of. This is a standard Wordpress install. The error was [27-Aug-2012 19:22:36 UTC] PHP NOTICE: Trying to get property of non-object. Just no script name or line number in the error I found that Wordpress' error logging contained the information to debug the problem, but that doesn't explain why the log didn't contain line number or script.

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  • What production-ready SaaS (recurring billing) solutions are available for Rails?

    - by Benjamin Manns
    I am working on a software-as-a-service (SaaS) application and I am looking for a billing plugin of some sort that will manage my subscriptions, customers, and recurring billing. There is the RailsKits SaaS kit ($249.00), but I prefer to use open source software. I have also found maccman's saasy, but the phrase "At the moment this is alpha code - use at your own risk" makes me a tad bit nervous.

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  • VS2010 Using SQL Server 2000

    - by Chris M
    Is there a way to use the SQL Model (dbml) builder in VS2010 using SQLServer2000? It works fine in VSExpress2008 + VS2008 but throws an "Upgrade SQL to 2005" error in VS2010 which seems a tad unreasonable.

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  • scite editor and gcc setting up?.

    - by sil3nt
    Hey there, In class we're using the Scite editor with gcc and its a tad outdated. I was wondering how you would "attach"(For lack of a better term) gcc to scite so that it would compile the code when I hit the compile icon?. Also would this process be the same when using other text editors like notepad++. -cheers.

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  • Is it possible to make WebLogic check REDEPLOY file more often?

    - by doublep
    [sorry for apparent shouting in the title, it's just that the file is named in all uppercase] Given advice in http://stackoverflow.com/questions/2695124 I successfully implemented and have been using autodeployment in WebLogic. This works great, but a tad too slow to my tastes, it seems like about 10 seconds pass between touching REDEPLOY file and WebLogic's start of redeployment. Is there any way I can instruct WebLogic to test timestamp on that file more often?

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  • The Best Way to Parse Dates from an Email

    - by John
    Im currently developing an app that can parse dates from an email - i.e extract the time and dates from an email (similar to gmail). Currently I do this in php but this is a tad clunky. Whats the best language to do this in and are there any existing open source solutions?

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  • Including SQL Server Express with Application

    - by Echilon
    I'm bundling an application for distribution and SQL Server is a prequisite so we're including SQL Server Express. What's the easiest way to include SQL server in a point and click installer? In the past I've used NSIS, but it was always flaky when installing the .NET Framework, so .NET, SQL Server and our app seems like an impossible task. It needs to be free, which probably cuts back my options a tad. Any suggestions or recommendations?

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  • Useful Qt Plugins

    - by Cenoc
    I'm a tad new to qt and so far I really only added qwt; but I was wondering, what are some other useful qt plugins? And is there a list somewhere? Thanks in advance.

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  • JQUERY, scrollTo, after scrolling down, the page won't let me scroll up for a second... Y?

    - by nobosh
    I'm using the following JQUERY to attach an even to a link in the header, which essentially scrolls to the bottom of the page: $('#comment-count-btn').click(function(){ $('html,body').scrollTo('#comment-wrapper', 500); }); Problem is, that it scrolls all the way to the bottom of the page (which is correct), but then when I try to scroll up a tad, the scroll bar jumps, as if it's locked for a little bit. Any ideas?

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  • What's making my page extend slightly beyond the viewport? [CSS]

    - by Jack W-H
    Basically I'm a tad confused. You'll see at http://furnace.howcode.com , in the second column, the bottom scrollbar button is extended slightly beyond the end of the viewport. I'm pretty confused as I've been examining the CSS and can't find anything that's causing this. Can you have a look? It's probably something simple that I've just missed! :) Screenshot:

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  • What production-ready SaaS (recurring billing) solutions are available for Rails?

    - by Benjamin Manns
    I am working on a software-as-a-service (SaaS) application and I am looking for a billing plugin of some sort that will manage my subscriptions, customers, and recurring billing. There is the RailsKits SaaS kit ($249.00), but I prefer to use open source software. I have also found maccman's saasy, but the phrase "At the moment this is alpha code - use at your own risk" makes me a tad bit nervous.

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