Re: [beagleboard] Why use C/C++ file I/O to access GPIO pins?

[Tim Cole]

So, I'm guessing it's a case of sacrificing performance for portability and 
robustness. My first reaction is that it seems odd, but then again --- make 
it work before you make it faster.
Thanks!


On Monday, August 18, 2014 1:54:39 PM UTC-4, Jerônimo Lopes wrote:
>
> I think...
>
> It's one of UNIX system base, that everything is a file.
> It is a common way of doing things in different platforms. For example: 
> gpio registers in 8051 are different from PIC, and different from AVR, and 
> so on. On a Linux (at least at user space), there is a common interface to 
> access gpio. Gives you much more portability. You can run the same code in 
> different processors.
>
> Jerônimo Lopes
>
>
>
> 2014-08-17 1:01 GMT-03:00 Tim
>
>> Greetings all,
>> I've been playing with software and hardware for 30+ years, but I'm new 
>> to Linux and embedded Linux systems. The code snippets I've been able to 
>> find for GPIO access all seem use file I/O functions. I've never seen this 
>> approach before -- I'm accustomed to reading and writing processor 
>> registers. The file I/O approach seems strange to me, but I'm new here, and 
>> there's a *lot *that seems strange.
>>
>> So, can someone explain why the file I/O approach is used? Is this a 
>> typical technique for Linux systems, or something particular to ARM 
>> processors? I suppose it doesn't really matter, but I prefer to understand 
>> why things are done as they are.
>>
>> Thanks very much, folks.
>>
>> Yours in newness,
>> Tim
>>
>>  -- 
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>
>

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Re: [beagleboard] Why use C/C++ file I/O to access GPIO pins?

[Tim Cole]

 I *do *tend to think in terms of basic microcontrollers where you 
have to make every clock cycle count. It looks like BBB is going to give me 
the luxury of clock cycles to spare. 

>From what I can gather, though, part of the problem in accessing the 
processor registers directly is that you'd have to run as root. Wouldn't 
you have the same problem with PRU access?


On Monday, August 18, 2014 3:46:44 PM UTC-4, William Hermans wrote:
>
> If you have something that just needs to switch something on / off once in 
> a while( less than 200 Hz ) why would you need to complicate things ? 
>
> If you need fast though, a PRU + mmap can achieve fairly "insane" speeds. 
> 10Mhz or better should not be a problem.
>
>
> On Mon, Aug 18, 2014 at 12:18 PM, Tim Cole  wrote:
>
>> So, I'm guessing it's a case of sacrificing performance for portability 
>> and robustness. My first reaction is that it seems odd, but then again --- 
>> make it work before you make it faster.
>> Thanks!
>>
>>
>>
>> On Monday, August 18, 2014 1:54:39 PM UTC-4, Jerônimo Lopes wrote:
>>
>>> I think...
>>>
>>> It's one of UNIX system base, that everything is a file.
>>> It is a common way of doing things in different platforms. For example: 
>>> gpio registers in 8051 are different from PIC, and different from AVR, and 
>>> so on. On a Linux (at least at user space), there is a common interface to 
>>> access gpio. Gives you much more portability. You can run the same code in 
>>> different processors.
>>>
>>> Jerônimo Lopes
>>>
>>>
>>>
>>> 2014-08-17 1:01 GMT-03:00 Tim
>>>
>>>> Greetings all,
>>>>
>>>> I've been playing with software and hardware for 30+ years, but I'm new 
>>>> to Linux and embedded Linux systems. The code snippets I've been able to 
>>>> find for GPIO access all seem use file I/O functions. I've never seen this 
>>>> approach before -- I'm accustomed to reading and writing processor 
>>>> registers. The file I/O approach seems strange to me, but I'm new here, 
>>>> and 
>>>> there's a *lot *that seems strange.
>>>>
>>>> So, can someone explain why the file I/O approach is used? Is this a 
>>>> typical technique for Linux systems, or something particular to ARM 
>>>> processors? I suppose it doesn't really matter, but I prefer to understand 
>>>> why things are done as they are.
>>>>
>>>> Thanks very much, folks.
>>>>
>>>> Yours in newness,
>>>> Tim
>>>>
>>>>  -- 
>>>> For more options, visit http://beagleboard.org/discuss
>>>> --- 
>>>> You received this message because you are subscribed to the Google 
>>>> Groups "BeagleBoard" group.
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>>>> an email to beagleboard...@googlegroups.com .
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>>>>
>>>
>>>  -- 
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>
>

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[beagleboard] How to determine hard float vs. soft float

[Tim Cole]

Greetings all
As I understand it, the Debian distribution installed on the most recent 
BBBs  is configured for hard float. If I were to install another flavor of 
Linux, or even an updated version of Debian, how would I determine if it's 
been configured to use hard float or soft float? Is there any way other 
than compiling with one option or the other and trying to make sense of the 
errors?

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Re: [beagleboard] Yet another newbie "how to get started"

[Tim Cole]

I'm probably going to kick myself for getting into this, but here goes 
nothing.

Getting into *any *new community can be difficult. You're the new kid and 
you don't know who's who. You wonder what's a sensible question, what's a 
naive question, and what's a bloody annoying question. I think most of us 
Linux newbies understand this. I'm trying to avoid asking the "bloody 
annoying" questions, but I imagine I'm going do it -- with luck, not often.

Part of the problem with figuring out how to climb the learning curve is 
that there's so *much *information. Saying its like "drinking from a fire 
hose" is cliched, but it feels like that sometimes. I realize that's a 
problem coming into *any *new area -- learning what's important and what's 
noise. I've decided -- tentatively -- that the Linux arena might be a bit 
worse than most. There's a tremendous amount of activity going on, and with 
that, a bit of anarchy, too. Perhaps that's typical of the entire 
open-source world, which also feels a bit odd to me. ("Hey, no problem, 
dude! There are parts all over this big, old garage, and anyone can build a 
car!") Having said that, I don't care to live in the near dictatorship of 
commercial OS communities. ("No, you can't do that. It takes arcane 
training and access to Secret Things. Now go away, buy the next version, 
and leave everything to the experts.")

It doesn't seem reasonable for anyone to expect all you more experienced 
folks to do a vast quantity of work for no compensation. (Feeling good 
about helping doesn't buy groceries.) On the other hand, being told to RTFM 
is pretty frustrating when you don't know what's a good manual or an 
outdated manual or just the equivalent of a scrawl on a notepad. And yes, I 
realize that knowing the difference comes with experience, too.

Speaking only for myself, I don't expect you to hold my hand and do 
everything for me. If I'm asking for too much, it's because I don't know 
I've done that. So, if this isn't too much to ask for (and I'm not trying 
to be snarky here), if anyone can suggest a newcomer's basic reading list 
and put that on a sticky post, it sure would help.

Cheers, Tim
 

On Thursday, September 4, 2014 1:56:32 PM UTC-4, William Hermans wrote:
>
> Funny thing is Don, If he ( assuming He because of the adversarial stance 
> ) took the time to read a book on the gcc toolchain he'd have figured it 
> out by now. But NOO, we must blame everyone else but ourselves, because 
> "we're" always right. RIGHT ?
>
>
>
>
> On Thu, Sep 4, 2014 at 10:49 AM, Don deJuan  > wrote:
>
>>  On 09/04/2014 09:14 AM, murr...@ameritech.net  wrote:
>>  
>>
>>
>>  So you want to compare a $45 board with a $375 one with a $1500 
>>> development license? Come on you can't be serious. Seems logic of a common 
>>> variety is lacking here.
>>>
>>> It's no ones fault but your own you're behind in the skills required for 
>>> your "homework" project. Step off the fricken high horse and re-evaluate 
>>> your gripes. If you can't hack the time it would take you to learn it give 
>>> up on your "homework" and tell your work to get someone more capable. It's 
>>> no ones job here to hold your little hand through your learning process, 
>>> especially for something it sounds like your work has given you. Everything 
>>> you need is at your finger tips, there are young kids figuring this out, so 
>>> if you've been around since the 80's developing, this should be no major 
>>> task at all to get going, so stop the complaining do some self research 
>>> learn the basics and get up to speed on what you're lacking. Posts like 
>>> these are just ridiculous. 
>>>  
>>
>>  This is the typical attitude of the Linux world, "Your too stupid to 
>> use my baby!" Its like some Masonic ritual, that all initiates must pass 
>> through because that's what the elders had to do.  I'm not asking anyone 
>> here to hold my hand.  I'm asking that you "elders" to organize, package, 
>> and document your work for the benefit of others.  This what any 
>> professional would do.  "Hack" is the key word here.  As long as this 
>> product lacks the proper tools to support it, like Linux, it will remain a 
>> hackers toy.
>>
>>  I agree that this is pointless.  So the final answer is "No" for all 
>> you lurkers out there who have the same frustrations but are afraid to 
>> chime in because you will get your head bit off.  To advance from a Newbie 
>> to a Novice, you must first become and Expert.
>>
>>  -- 
>> For more options, visit http://beagleboard.org/discuss
>> --- 
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>>
>>
>> And your replies and statements are typical of those who ride that 
>> entitled horse and want everything for free including their knowledge.

Re: [beagleboard] Re: How to determine hard float vs. soft float

[Tim Cole]

I have no idea why, but I've got both an arm-linux-gnueabihf directory and 
an arm-linux-gnueabi (i.e no "hf') directory. From what you've said, I'd 
guess I've installed something I shouldn't have installed. Presumably, if I 
check immediately after installing a new OS, I wouldn't have the problem.

Much obliged, folks.



On Thursday, September 4, 2014 3:58:08 PM UTC-4, William Hermans wrote:
>
> Heh, another way I just figured out ( never noticed it before ) is to just 
> do . . 
>
> $ ls /lib/
>
> there is a arm-linux-gnueabihf directory and a ld-linux-armhf.so.3 file. 
> Both of these should make it painfully obvious.
>
>

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Re: [beagleboard] Using cape .dts with latest kernel 3.15.10.

[Tim Cole]

This is probably a very naive question, but I'm leery of mucking about with 
installing a new kernel until I know for sure. Can the 3.15.10 kernel (or 
any other, for that matter) be installed without wiping out the rest of the 
OS?

Cheers, Tim


On Wednesday, September 3, 2014 11:29:50 AM UTC-4, RobertCNelson wrote:
>
> On Tue, Sep 2, 2014 at 10:15 PM, Randy Graham  > wrote: 
> > Hello, 
> > 
> > I have a custom cape that worked with Cape Manager and the 3.8 kernel 
> and 
> > would like to move to Robert Nelson's latest kernel, 3.15.10. 
> > 
> > Since there is no Cape Manager for the later kernels, what is the proper 
> > method for adding my cape .dts file to the build? 
> > 
> > Can I simply include my .dts file at the end of am335x-bone.dts ? 
> > 
> > Do I need to modify my cape .dts file at all ? 
>
> So I've been spending some time cleaning up things for cape users: 
>
> http://elinux.org/Beagleboard:Capes_3.8_to_3.14 
>
> Once you install that kernel, you can then clone the "dtb-rebuilder" 
>
> http://elinux.org/Beagleboard:Capes_3.8_to_3.14#Custom_dtb 
>
> make your changes to either (depending on what board you have): 
>
> src/arm/am335x-bone.dts 
> src/arm/am335x-boneblack.dts 
>
> Then just: 
>
> make 
> sudo make install 
>
> (reboot) 
>
> Note it's tied to newer file system: 
>
>
> http://elinux.org/Beagleboard:BeagleBoneBlack_Debian#Debian_Image_Testing_Snapshots
>  
>
> for, these two features: 
> (kernel): sudo apt-get install linux-image-xyz 
> (dtb-rebuilder): sudo make install 
>
> Regards, 
>
> -- 
> Robert Nelson 
> http://www.rcn-ee.com/ 
>

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Re: [beagleboard] Using cape .dts with latest kernel 3.15.10.

[Tim Cole]

Much obliged, Robert!


On Thursday, September 4, 2014 5:57:06 PM UTC-4, RobertCNelson wrote:
>
> On Thu, Sep 4, 2014 at 4:54 PM, Tim Cole > 
> wrote: 
> > This is probably a very naive question, but I'm leery of mucking about 
> with 
> > installing a new kernel until I know for sure. Can the 3.15.10 kernel 
> (or 
> > any other, for that matter) be installed without wiping out the rest of 
> the 
> > OS? 
>
> Correct.. As long as it atleast boots with the new kernel you can 
> change it back.. 
>
> I'm setting up things, so all you have to do is: 
>
> sudo apt-get install linux-image-$version 
> sudo reboot 
>
> later edit /boot/uEnv.txt (uname_r variable) and then boot any 
> $version installed.. 
>
> Regards, 
>
> -- 
> Robert Nelson 
> http://www.rcn-ee.com/ 
>

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Re: [beagleboard] Yet another newbie "how to get started"

[Tim Cole]

Agreed -- you can't learn a damned thing without putting in your own skull 
time. Perhaps I'm too distrustful of internet search engines -- I like a 
good reference handbook. If there isn't one available, I'll just have to 
make do.


On Thursday, September 4, 2014 6:24:04 PM UTC-4, William Hermans wrote:
>
> Tim, what you need to do is figure out what you want to do, and then start 
> googling / reading. There is no "easy reading list" because no one thinks 
> just like you ( or me / anyone else for that matter ).
>
> I understand this is not very optimal, especially if you have a deadline. 
> But that is how it works. Just be glad that today there is far more 
> information out there than there was at the initial launch last year.
>
> For instance, I spent 2-3 weeks reading how uEnv.txt and uboot worked well 
> enough to make custom changes of my own. *Before* I knew enough to ask 
> Robert a specific enough question to get a good answer. Also, this answer 
> was not a hold my hand step by step answer, it was a link to the uboot 
> config header file for the beaglebone/ beaglebone black.
>
> Anyway, the moral of the story is this. Teach yourself to teach yourself. 
> Or, in other words, learn how to think for yourself. I understand learning 
> by example all to well myself ( I hate walls of text, when a proper example 
> can explain all ). However and example does not necessarily teach you 
> anything. The ole give a man a fish versus teach a man to fish analogy . . .
>
>
>
>

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Re: [beagleboard] Yet another newbie "how to get started"

[Tim Cole]

Thanks, John --- just the sort of thing I've been looking for. As far as 
kernel development goes, I think I'll stick to popcorn for quite some time. 
;-)
Cheers, Tim


On Friday, September 5, 2014 12:38:22 AM UTC-4, john3909 wrote:
>
>
> From: Tim Cole >
> Reply-To: "beagl...@googlegroups.com " <
> beagl...@googlegroups.com >
> Date: Thursday, September 4, 2014 at 2:41 PM
> To: "beagl...@googlegroups.com "  >
> Subject: Re: [beagleboard] Yet another newbie "how to get started"
>
> I'm probably going to kick myself for getting into this, but here goes 
> nothing.
>
> Getting into *any *new community can be difficult. You're the new kid and 
> you don't know who's who. You wonder what's a sensible question, what's a 
> naive question, and what's a bloody annoying question. I think most of us 
> Linux newbies understand this. I'm trying to avoid asking the "bloody 
> annoying" questions, but I imagine I'm going do it -- with luck, not often.
>
> Part of the problem with figuring out how to climb the learning curve is 
> that there's so *much *information. Saying its like "drinking from a fire 
> hose" is cliched, but it feels like that sometimes. I realize that's a 
> problem coming into *any *new area -- learning what's important and 
> what's noise. I've decided -- tentatively -- that the Linux arena might be 
> a bit worse than most. There's a tremendous amount of activity going on, 
> and with that, a bit of anarchy, too. Perhaps that's typical of the entire 
> open-source world, which also feels a bit odd to me. ("Hey, no problem, 
> dude! There are parts all over this big, old garage, and anyone can build a 
> car!") Having said that, I don't care to live in the near dictatorship of 
> commercial OS communities. ("No, you can't do that. It takes arcane 
> training and access to Secret Things. Now go away, buy the next version, 
> and leave everything to the experts.")
>
> It doesn't seem reasonable for anyone to expect all you more experienced 
> folks to do a vast quantity of work for no compensation. (Feeling good 
> about helping doesn't buy groceries.) On the other hand, being told to RTFM 
> is pretty frustrating when you don't know what's a good manual or an 
> outdated manual or just the equivalent of a scrawl on a notepad. And yes, I 
> realize that knowing the difference comes with experience, too.
>
> Speaking only for myself, I don't expect you to hold my hand and do 
> everything for me. If I'm asking for too much, it's because I don't know 
> I've done that. So, if this isn't too much to ask for (and I'm not trying 
> to be snarky here), if anyone can suggest a newcomer's basic reading list 
> and put that on a sticky post, it sure would help.
>
> Start by reading a few good books on the topic. Here are a few that I have 
> found helpful:
>
> Linux System Programming: Talking Directly to the Kernel and C Library by 
> Robert Love
> The Linux Programming Interface: A Linux and UNIX System Programming 
> Handbook by Michael Kerrisk
> Linux Kernel Development (3rd Edition) by Robert Love
>
> Once you have read these books, you will be in pretty good shape. If you 
> want to do kernel driver development, there are no good solutions as they 
> all tend to be somewhat outdated but they do give you the basics:
>
> Essential Linux Device Drivers by Sreekrishnan Venkateswaran
> Linux Device Drivers (3rd Edition) by Jonathan Corbet, Alessandro Rubini 
> and Greg Kroah-Hartman
>
> An updated version of the last book is in the work, but it was original 
> scheduled for late 2014, but it has now scheduled for sometime in 2015.
>
> Regards,
> John
>
>
>

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[beagleboard] Re: Welcome the Fall 2014 Beagle Class to the group

[Tim Cole]

This course *does* look interesting. Is there any way to audit the course 
-- uStream archives or something like that?
Cheers, Tim



On Friday, September 5, 2014 11:13:58 AM UTC-4, Mark A. Yoder wrote:
>
> The purpose of this posting is to announce that I'm once again teaching 
> an Embedded Linux class based on the BeagleBone Black [1].  I'm 
> teaching as open-source as I can and have have posted many of course 
> materials on eLinux.org [2] and github[3].
>
> I'm always open to ideas on what topics to include in the class and 
> suggestions for interesting course projects.  For example we are starting
> BoneScript today and hope to be writing simple kernel module 5 weeks from 
> now.
>
> Class, please respond to this posting.  Others, please welcome my class.
>
> --Mark 
>
> --Prof. Mark A. Yoder 
>   Rose-Hulman Institute of Technology [4] 
>
> [1] http://elinux.org/Embedded_Linux,_Rose-Hulman 
> [2] http://elinux.org/index.php?title=Category:ECE597 
> [3] https://github.com/MarkAYoder/BeagleBoard-exercises 
> [4]  http://www.rose-hulman.edu 
>

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Re: [beagleboard] Re: Yet another newbie "how to get started"

[Tim Cole]

Once again --- thanks, folks. It's always useful to have some "trail 
markers" from explorers who've gone before. It certainly seems odd to have 
open resources that aren't just thinly veiled ads, but it seems that's not 
unusual in the Land of Linux. Who'd have guessed? :-)

(If you'll pardon the digression, I'm reminded of a joke that makes more 
sense to me now. A Windows user says, "Oh, crap! Windows is downloading 
another update!" A Linux user says, "Oh, just the usual updates." A Mac 
user says, "Oh, wow! An update! And it's only a hundred dollars!")

Cheers, Tim


On Friday, September 5, 2014 12:56:21 PM UTC-4, William Hermans wrote:
>
> You can find free legitimate reading material easily on the web. LDD ( 
> Linux Device Drivers is one example ). 
>
> Not to mention sites like 
>
> http://www.debianhelp.co.uk/ddcommand.htm and 
> https://wiki.debian.org/NetworkConfiguration
>
> Note that both those came up off of a google search, so yeah google is 
> probably the most important resource.
>
>
>
>
> On Fri, Sep 5, 2014 at 7:11 AM, Joshua Datko  > wrote:
>
>>
>>
>> Tim Cole > 
>> writes:
>>
>> > Agreed -- you can't learn a damned thing without putting in your own
>> > skull time. Perhaps I'm too distrustful of internet search engines --
>> > I like a good reference handbook. If there isn't one available, I'll
>> > just have to make do.
>>
>> By far, the number one reference on the BeagleBone Black is the System
>> Reference Manual:
>>
>> https://github.com/CircuitCo/BeagleBone-Black/blob/master/BBB_SRM.pdf?raw=true
>>
>> It's impressively complete.
>>
>> However, that mainly covers the hardware. Since hardware doesn't change
>> as often as software (although it's becoming more that way) any other
>> reference is a snapshot in time, especially for Linux resources.
>>
>> In increasing specificity, one would need (supplied with links to books
>> I like):
>>
>> - A good Linux reference
>> http://www.nostarch.com/howlinuxworks.htm
>>
>> - A good Debian reference
>> http://www.nostarch.com/debian.htm
>>
>> - A good embedded Linux reference
>> http://www.amazon.com/Linux-Embedded-Systems-Experts-Voice/dp/1430272279
>>
>> - A good Linux programming reference
>> http://www.nostarch.com/tlpi
>>
>> The difficulty in writing books on the BeagleBone is that the community
>> moves incredibly fast. This is the sign of a healthy and vibrant
>> community.
>>
>> Josh
>>
>> p.s. There are, of course, great *free* resources too. One would have to
>> use a distrustful search engine to find them :p
>>
>> --
>> For more options, visit http://beagleboard.org/discuss
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>
>

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[beagleboard] Re: Start QT Application on bootup on Beaglebone Black

[Tim Cole]

You've accomplished more than I've managed to do. Could you suggest some 
references I could check so I can figure out what silly mistakes I'm making?

Cheers, Tim


On Tuesday, September 9, 2014 3:57:58 AM UTC-4, Mickae1 wrote:
>
> you should switch to debian, you will have more help from the Debian 
> community . I've a BBB under debian which start QT at bootup !
>
> Micka,
>
> Le dimanche 7 septembre 2014 14:03:35 UTC+2, Mahendra Gunawardena a écrit :
>>
>>
>> Below is picture of the display on bootup. Expected display output is 
>> overwritten by Angstrom screen 
>>
>>
>> 
>> Expected Display output
>>
>>
>> 
>> The expected display output briefly appears but is overwritten by the 
>> Angstrom text based image. But occasionally the expected display 
>> appears. Then the dynamic widgets update the screen but the static 
>> information is not visible. The issues appears to be timing, and if the 
>> BBB can be forced to start the QT application after complete bootup of BBB 
>> that would suffices the current needs.
>>  
>> Application is been started as a service. Below is the content of the 
>> service file
>>
>> [Unit]
>> Description=QTAccelerometer GUI
>> After=systemd-user-sessions.service
>>
>> [Service]
>> WorkingDirectory=/home/root/projects/qt-projects
>> ExecStart=/home/root/projects/qt-projects/QTAccelerometer -qws
>> SyslogIdentifier=QTAccelerometer
>> Restart=on-failure
>> RestartSec=5
>>
>> [Install]
>> Alias=display-manager.service
>>
>>
>> Below are the other options tried without success
>>
>> [Install]
>> WantedBy=multi-user.target
>> WantedBy=graphical.target
>>
>>
>> *References*
>>
>>- Creating Ångström System Services on BeagleBone Black 
>>
>>
>> I have also posted this question on Stackoverflow 
>> 
>> .
>>
>> Thank you in advance
>>
>> Mahen
>>
>

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Re: [beagleboard] Re: Start QT Application on bootup on Beaglebone Black

[Tim Cole]

Thanks! That's more grist for my slowly grinding mental mill


On Thursday, September 11, 2014 3:29:15 PM UTC-4, Mahendra Gunawardena 
wrote:
>
> Tim,
>
> Please look the this stackoverflow questions and response
>
> Start QT Application on bootup on an Embedded Linux Device (Beaglebone 
> Black) 
> <http://stackoverflow.com/questions/25701662/start-qt-application-on-bootup-on-an-embedded-linux-device-beaglebone-black>
>
> Based on this input I was able to resolve the issue. I will post my end 
> solution in due course.
>
>
>
> *
>
> Mickae1 and Maxim
>
> I do understand Angstrom distribution is something in the past. Have a 
> come across a good source to configure QT development for BBB/Debian on a 
> Host Ubuntu. 
>
> I used Derek Molloy suggestions and it worked well for QT development for 
> BBB/Angstrom on Host Ubuntu. 
>
> I do understand that I need to make the change BBB/Debian.
>
> Thank you for all the great input.
>  
>
>
> On Wed, Sep 10, 2014 at 8:52 PM, Tim Cole 
> > wrote:
>
>> You've accomplished more than I've managed to do. Could you suggest some 
>> references I could check so I can figure out what silly mistakes I'm making?
>>
>> Cheers, Tim
>>
>>
>>
>> On Tuesday, September 9, 2014 3:57:58 AM UTC-4, Mickae1 wrote:
>>>
>>> you should switch to debian, you will have more help from the Debian 
>>> community . I've a BBB under debian which start QT at bootup !
>>>
>>> Micka,
>>>
>>> Le dimanche 7 septembre 2014 14:03:35 UTC+2, Mahendra Gunawardena a 
>>> écrit :
>>>>
>>>>
>>>> Below is picture of the display on bootup. Expected display output is 
>>>> overwritten by Angstrom screen 
>>>>
>>>>
>>>> <https://lh6.googleusercontent.com/-0ZA2QPRpNi8/VAxGxNd11yI/ABs/lvJbktseYgY/s1600/IMG_3852.JPG>
>>>> Expected Display output
>>>>
>>>>
>>>> <https://lh4.googleusercontent.com/-6jEzdpYTOQ0/VAxG86ZQFzI/AB0/LcFlyIPkwfE/s1600/IMG_3853.JPG>
>>>> The expected display output briefly appears but is overwritten by the 
>>>> Angstrom text based image. But occasionally the expected display 
>>>> appears. Then the dynamic widgets update the screen but the static 
>>>> information is not visible. The issues appears to be timing, and if 
>>>> the BBB can be forced to start the QT application after complete bootup of 
>>>> BBB that would suffices the current needs.
>>>>  
>>>> Application is been started as a service. Below is the content of the 
>>>> service file
>>>>
>>>> [Unit]
>>>> Description=QTAccelerometer GUI
>>>> After=systemd-user-sessions.service
>>>>
>>>> [Service]
>>>> WorkingDirectory=/home/root/projects/qt-projects
>>>> ExecStart=/home/root/projects/qt-projects/QTAccelerometer -qws
>>>> SyslogIdentifier=QTAccelerometer
>>>> Restart=on-failure
>>>> RestartSec=5
>>>>
>>>> [Install]
>>>> Alias=display-manager.service
>>>>
>>>>
>>>> Below are the other options tried without success
>>>>
>>>> [Install]
>>>> WantedBy=multi-user.target
>>>> WantedBy=graphical.target
>>>>
>>>>
>>>> *References*
>>>>
>>>>- Creating Ångström System Services on BeagleBone Black 
>>>><http://mattrichardson.com/BeagleBone-System-Services/>
>>>>
>>>> I have also posted this question on Stackoverflow 
>>>> <http://stackoverflow.com/questions/25701662/start-qt-application-on-bootup-on-an-embedded-linux-device-beaglebone-black>
>>>> .
>>>>
>>>> Thank you in advance
>>>>
>>>> Mahen
>>>>
>>>  -- 
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[beagleboard] Re: Issue getting DS18B20 temperature sensor working

[Tim Cole]

You can use either powered or parasitic modes for One-Wire devices -- there 
isn't a distinct device for one mode or the other. The data sheet shows the 
DS18B20 can operate down to 3V.

I'm not greatly versed in embedded Linux, nor in the BBB, but I've used 
One-Wire devices (including DS18S20s) a fair bit. I avoid parasitic mode 
whenever I can. Running a power line makes One-Wire systems much easier to 
debug, and multi-wire cables aren't all that expensive.

Cheers, Tim


On Sunday, September 28, 2014 5:48:11 AM UTC-4, Michaël Vaes wrote:
>
> I was able to get the sensor showing up (switched + and -... Yeah to 
> quick), however I'm not able to get correct temperature readings with a new 
> sensor.
> I need to mention that I have the Parasitic version DS18B20+, does that 
> work with 3.3VDC or do I need to connect it to 5VDC (which the BBB does not 
> support I believe, 5VDC inputs..)
>
> root@bbb:~# for i in `find /sys/devices/w1_bus_master1/ -type d -iname 
> "28-*"`; do echo -n $i' '; grep -oE "t=[0-9]+$" "$i/w1_slave"; done;
> /sys/devices/w1_bus_master1/28-057ee219 t=85000
> /sys/devices/w1_bus_master1/28-057efe1e t=85000
>
> Thanks,
> *Michaël*
>
>
> On Saturday, August 30, 2014 1:01:18 PM UTC+2, Michaël Vaes wrote:
>>
>> Hi -
>>
>> I'm stuck getting my DS18B20 temperature sensor working on my Beaglebone 
>> Black.  I installed and loaded the DTC overlay but Im not getting the '28-*'
>> files in my '/sys/devices/w1_bus_master1/' directory.
>>
>> *Wiring*
>>
>> https://dl.dropboxusercontent.com/u/97513059/ds18b20-temperature-sensor.pdf
>>
>> *Software*
>> Debian 7.6
>> Kernel: 3.8.13-bone50
>>
>> *My sensor:* http://www.mouser.com/ds/2/256/DS18B20-28978.pdf
>> *My DTS file:* http://pastebin.com/ma7qd6HK
>>
>> *Latest version of dtc: *https://raw.githubusercontent.com/RobertCNelson/
>> tools/master/pkgs/dtc .sh 
>>
>> *Install*
>> root@bbb:~# cat one-wire-temp-sensor_p8-11.sh
>> #!/bin/bash
>> #
>> # BBB One Wire Temperature sensor (DS18B20)
>> #
>>
>> sName='w1';
>> sInput=$sName'.dts';
>> sOutput=${sName:0:16}'-00A0.dtbo';
>>
>>
>> # Build
>> /usr/local/bin/dtc -O dtb -o "$sOutput" -b 0 -@ "$sInput";
>> cp $sOutput /lib/firmware/;
>> echo "$sName" > /sys/devices/bone_capemgr.9/slots;
>>
>> *GPIO's*
>> Pin P8.11 gets high, when I test the voltage it's 3.3VDC.
>> root@bbb:~# cat /sys/kernel/debug/gpio
>> GPIOs 0-31, gpio:
>>  gpio-6   (mmc_cd  ) in  lo
>>
>> GPIOs 32-63, gpio:
>>  gpio-45  (w1  ) in  hi
>>  gpio-52  (eMMC_RSTn   ) out lo
>>  gpio-53  (beaglebone:green:usr) out lo
>>  gpio-54  (beaglebone:green:usr) out lo
>>  gpio-55  (beaglebone:green:usr) out hi
>>  gpio-56  (beaglebone:green:usr) out lo
>>
>> GPIOs 64-95, gpio:
>>
>> GPIOs 96-127, gpio:
>>
>> *Overlays*
>> HDMI disabled, w1 overlay loaded
>> root@bbb:~# cat /sys/devices/bone_capemgr.9/slots
>>  0: 54:PF---
>>  1: 55:PF---
>>  2: 56:PF---
>>  3: 57:PF---
>>  4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
>>  5: ff:P-O-- Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
>>  6: ff:P-O-- Bone-Black-HDMIN,00A0,Texas Instrument,BB-BONELT-HDMIN
>>  7: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-UART1
>>  8: ff:P-O-L Override Board Name,00A0,Override Manuf,w1
>>
>> *dmesg*
>> root@bbb:~# dmesg | tail -n11
>> [  167.078501] bone-capemgr bone_capemgr.9: part_number 'w1', version 
>> 'N/A'
>> [  167.078681] bone-capemgr bone_capemgr.9: slot #8: generic override
>> [  167.078726] bone-capemgr bone_capemgr.9: bone: Using override eeprom 
>> data at slot 8
>> [  167.078775] bone-capemgr bone_capemgr.9: slot #8: 'Override Board 
>> Name,00A0,Override Manuf,w1'
>> [  167.079020] bone-capemgr bone_capemgr.9: slot #8: Requesting part 
>> number/version based 'w1-00A0.dtbo
>> [  167.079067] bone-capemgr bone_capemgr.9: slot #8: Requesting firmware 
>> 'w1-00A0.dtbo' for board-name 'Override Board Name', version '00A0'
>> [  167.082029] bone-capemgr bone_capemgr.9: slot #8: dtbo 'w1-00A0.dtbo' 
>> loaded; converting to live tree
>> [  167.082504] bone-capemgr bone_capemgr.9: slot #8: #2 overlays
>> [  167.089775] of_get_named_gpio_flags exited with status 45
>> [  167.089820] of_get_named_gpio_flags: can't parse gpios property
>> [  167.097793] bone-capemgr bone_capemgr.9: slot #8: Applied #2 overlays.
>>
>> *Tryouts without success*
>>
>>- Reboots :o)
>>- Using another temperature sensor
>>- Updating the OS
>>- Changing the DTS file to use another pin like 'P9.22'
>>   - 
>>   
>> http://hipstercircuits.com/dallas-one-wire-temperature-reading-on-beaglebone-black-with-dto/
>>   - Changing 'gpios = <&gpio2 13 0>;' to 'gpios = <&gpio1 13 0>;'
>>
>> *What concerns me and where I cannot seem to get rid of in dmesg> ...
>
>

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[beagleboard] Re: Beagle Bone Black Dog Standoff Dog Feet

[Tim Cole]

Now there's a great visual pun!

On Sunday, September 28, 2014 10:37:16 PM UTC-4, John Kollman wrote:
>
>
> https://www.shapeways.com/model/2670740/dogfeet11.html?materialId=6
>
> I created some dog feet standoffs for my beagle board black. Made them 
> available at shapeways if anyone wants a set. I think they are cute. 
>
> Thanks
>

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