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eschaton posted:In the under $100 category, ARM still rules for overall price/performance, even if the Raspberry Pi isn't very performance for the price. I await my Dragonboard 410c… $100 is just an arbitrary number. For another $20 you hit the price-point of the Liva X. Once you factor in all the crap that comes with the Liva the pricepoint of the Pi2 is at least $60, so the Liva X is about 4x faster at less than 2x the cost. The original Liva is a bit slower but they're getting cleared out for around $100 nowadays. You can even start throwing together a low-end homebuilt system for not too much more than that. Mobo with J1900 or AM1 combo from Fry's - $60, Rosewill RS MI 01 case with PSU - $50, 2GB DDR3 SODIMM - $15, 64GB SSD - $30. So about $150 for something that's ~3x as powerful as the Liva X, and it'll smoke the poo poo out of a Pi2. That's actually more or less what I built to replace the Pi I tried to use as a home server, and it's very decent in this role. The Pi2's main charm is that it hits a $35 price point for nerds who can pull everything they need out of their junk closet. The words "performance" shouldn't be uttered anywhere near the words "Raspberry Pi", because ARM gets absolutely destroyed by even the garbage-tier x86 stuff that's around $100, even if we're charitable and use a price-to-performance metric. Paul MaudDib fucked around with this message at 16:37 on Aug 19, 2015 |
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Aug 19, 2015 16:25
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To be fair, the performance increase I've seen from the Pi1 B to Pi2 B is very real. But you're still right 
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Aug 19, 2015 16:37
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I think what I would like about the computestick and the HP is that they'd run silent, sip on power consumption, and take up next to no space when headless. Those plus cost are what I'd be looking for when graduating from the Pi. Plus probably decent Linux support.
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Aug 19, 2015 18:02
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doctorfrog posted:I think what I would like about the computestick and the HP is that they'd run silent, sip on power consumption, and take up next to no space when headless. Those plus cost are what I'd be looking for when graduating from the Pi. Plus probably decent Linux support. They aren't silent, they've got a 1 inch fan which does make some noise when the get hot (happens fairly quickly). Nowhere near as bad as a desktop PC or laptop though. Agree with the rest.
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Aug 19, 2015 18:05
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Well that HP Stream is getting cheaper. $150 on Woot currently. http://computers.woot.com/offers/hp-stream-mini-intel-dual-core-desktop-1?ref=cnt_wp_5_1 Edit: refurb.
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Aug 19, 2015 18:25
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I think y'all are missing the point I'm making, and vastly overestimating the computer skills of the teachers (and assuming all these primary schools have a dedicated IT team to mess around with setting all this stuff up, or make purchasing decisions based on SATA throughput). It's a little box with pins you can connect stuff to, and it comes with a visual programming language that lets kids (and teachers) get a handle on basic principles and still actually do something interesting on the screen or in the real world. It's small and light enough to stick inside things you build. You can plug it into an old TV if that's all you have. It's cheap enough for kids to take outside the school, and if/when anything goes wrong it's no big loss. It comes with friendly documentation, and projects, and lesson plans, and a community based around using it in an education setting. Fixing 'software problems' or replacing the Pi itself is as simple as swapping out the SD card. For what it is, it can do an incredible amount and has a ton of potential, which is why it's been such a big hit. It's nowhere near perfect, and for technical people (and schools with decent IT support) there may be better options now - which again, really depends on who's going to be using it, the background of the teacher, the available educational material, and what they need to do with it. But all that stuff up there is why they created the Pi, so it's a bit weird to say 'using Pis as school computers never made sense' when that's exactly the situation they were specially designed for. They're not intended to replace all the PCs in the computer lab or anything
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Aug 19, 2015 18:29
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baka kaba posted:I think y'all are missing the point I'm making, and vastly overestimating the computer skills of the teachers (and assuming all these primary schools have a dedicated IT team to mess around with setting all this stuff up, or make purchasing decisions based on SATA throughput). I think you're vastly underestimating the abilities of teachers in schools that have already had computers for at least a decade if not more. Or the difficulty of teaching computer stuff when your district simply shells out for training the teachers instead of buying a bunch of Raspberry Pis and the neccesary equipment to actually use them. Kids can't actually take the devices outside school and use them effectively without also having spare equipment at home, which most of them won't have. And the pins are utterly irrelevant to teaching basic computer stuff. The actual computers your schools have will have plenty of visual programming languages and other such things to use. The Raspberry Pi is in no way easier for your random school teacher to use then the computers they already have access to. They may have tried to design them for that, but they failed.
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Aug 19, 2015 18:41
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If you get a compute stick and some sort of bus pirate over USB, aren't you pretty limited on the code that executes direct on the bus pirate board just a few kb of code? I ask because if you're listening for an event over I2C which might be running at 2Mhz and USB only runs at 500mhz, that's a long time comparatively. I guess as long as it's faster than 100hz it's "real time" as far as the human brain is concerned. But if you start stacking things running in the Mhz range, and at the end of your logic chain is being run by an x86 cpu, filtered out with only 500 updates a second you can get some crappy performance hits. Intel CPUs do have I2C, SPi and GPIO, but it's mostly not break-out-able I remember seeing some old blank ISA boards that basically gave you access to the CPU's GPIO via ISA and were just an ISA to breadboard adapter, it would be neat to do something similar with PCIE. Hadlock fucked around with this message at 18:52 on Aug 19, 2015 |
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Aug 19, 2015 18:48
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Nintendo Kid posted:It reminds me of the original OLPC. They decided to make it gimmicky with some custom Linux OS, then when the actual people who would be receiving them finally got a say, they're like "well we would really prefer if it had a normal OS, preferably Windows, so that we can use the same things the rich folks can". I once tried out the OLPC interface in a VM to see what they'd come up with. I couldn't make heads or tails of it. Everything was an overly-abstracted icon and I never did figure out what most of them were. I'll assume it makes sense if you get some instruction in it. But the kids who learn this interface will grow up and be prepared for... what, exactly?
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Aug 19, 2015 19:00
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Nintendo Kid posted:I think you're vastly underestimating the abilities of teachers in schools that have already had computers for at least a decade if not more. Or the difficulty of teaching computer stuff when your district simply shells out for training the teachers instead of buying a bunch of Raspberry Pis and the neccesary equipment to actually use them. Yeah I don't think you exactly get the UK situation here. Teachers (especially in primary school - that's elementary school to you, required to cover all subjects) have been increasingly expected to teach computer science to kids, and now it's mandated as part of the National Curriculum. There's almost no actual support for teachers, never mind organised training to prepare them to teach the material. That's why packages like the Pi (and its associated documentation and teaching materials) are so appealing, and that's the difference between the Pi and some other random small computer And if you think the pins are irrelevant, you have no idea what schools are actually doing with them (and why)
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Aug 19, 2015 19:53
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Hadlock posted:If you get a compute stick and some sort of bus pirate over USB, aren't you pretty limited on the code that executes direct on the bus pirate board just a few kb of code? I ask because if you're listening for an event over I2C which might be running at 2Mhz and USB only runs at 500mhz, that's a long time comparatively. I guess as long as it's faster than 100hz it's "real time" as far as the human brain is concerned. But if you start stacking things running in the Mhz range, and at the end of your logic chain is being run by an x86 cpu, filtered out with only 500 updates a second you can get some crappy performance hits. Can you give a specific example? The Bus Pirate can do frequency counting up to 40 MHz which is vastly more than the 1 MHz a Pi can deliver. It can also do logic analysis at up to 1 MHz on 8 channels with a 4096-sample buffer onboard. That's not super high-end relative to real logic analysers but its easily capable of sniffing I2C traffic and so on (sniffing arbitrary bits is much harder than sending/receiving a known protocol). It can also do PWM for servos, frequency generation, etc. Generally speaking the Bus Pirate is not just a serial adapter, it's a little microcontroller all on its own and works best when used like that. The Pi isn't a good fit for demanding hard-realtime applications anyway. You really want a microcontroller for that. There's two different educational applications that are being conflated here. One is "cheap desktop computer for learning Python" and the other is "cheap micro for embedded applications". The Pi isn't particularly good at either of these, but there's a bit more of a case for the latter given the GPIO capabilities. The fact that it lacks onboard WiFi capability, can't deliver enough USB power for many adapters, and had a broken USB stack for a couple years kinda screws it for that use though, especially since its competitors do provide those things. Arduino<->ZigBee<->BT dongle is pretty damned easy to do nowadays too, and is a lot better " real world" approach once we're past Babby's First Blinking LED. And again if you have access to a desktop or laptop then a Bus Pirate is just as easy to use as a standalone SoC computer, much more capable than a Pi, and costs like <$30 a pop. Paul MaudDib fucked around with this message at 20:44 on Aug 19, 2015 |
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Aug 19, 2015 20:01
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baka kaba posted:Yeah I don't think you exactly get the UK situation here. Teachers (especially in primary school - that's elementary school to you, required to cover all subjects) have been increasingly expected to teach computer science to kids, and now it's mandated as part of the National Curriculum. There's almost no actual support for teachers, never mind organised training to prepare them to teach the material. That's why packages like the Pi (and its associated documentation and teaching materials) are so appealing, and that's the difference between the Pi and some other random small computer Ok, and? Having GPIO pins is irrelevant to teaching computer science. Your schools already have computers, the Pi is unnecessary. The Pi foundation should give up thwir quixotic quest to tie the education stuff to the Pi itself, because free open source virtual machines could be used to run the same sorts of things on any modern computer, or even any computer built since 1999. So you wouldn't have a physical LED to flash, big deal! Why do you keep insisting on only comparing the pi to "small computers"? I don't see anything in your national curriculum that dictates computer science must be taught on needlessly small computers instead of the computers your schools already have. Is this just some long standing fetishization of the old school BBC Micro and similar, and assuming that modern students should learn on something similarly limited?
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Aug 19, 2015 20:22
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Nintendo Kid posted:Having GPIO pins is irrelevant to teaching computer science. Wrong. Even more wrong if you're talking about Artificial Intelligence / Robotics in a Computer Science background driven capacity. 
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Aug 19, 2015 20:36
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But CS doesn't even necessitate actually touching a computer. Are you thinking of engineering?
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Aug 19, 2015 20:45
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^ these are 5-year-olds and upNintendo Kid posted:Why do you keep insisting on only comparing the pi to "small computers"? I don't see anything in your national curriculum that dictates computer science must be taught on needlessly small computers instead of the computers your schools already have. Is this just some long standing fetishization of the old school BBC Micro and similar, and assuming that modern students should learn on something similarly limited? Because it's a computer that's small. It can go in things, like all the stuff kids are building in schools, as a programmable embedded controller, etc Funny you mention the BBC and it's limitations, we used Logo on them. It was shite. Kids are doing way more interesting and relevant stuff with the Pi, getting a far broader education, and that's a great thing Nintendo Kid posted:And Java's easy enough by far. Or again, python, logo, and other things. 
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Aug 19, 2015 20:45
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eightysixed posted:Wrong. You have no idea what computer science is about then. Are you confusing it with hardware engineering? You can get a drat Ph.d in the subject without ever doing hardware stuff. eightysixed posted:Even more wrong if you're talking about Artificial Intelligence / Robotics in a Computer Science background driven capacity. baka kaba posted:
You can also just actually buy things that are meant to go into other things, and use your already existing computers for teaching computer science stuff. poo poo you can buy legos with integrated control stuff. What's supposed to be ironic on that? When I was a kid we used it on the same computers we used Word and the internet on.
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Aug 19, 2015 20:47
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It's ironic that you call the Pi limited like the BBC, after advocating kids learning Logo (a BBC staple) instead of all the cool, engaging stuff the Pi and its ecosystem is allowing them to do
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Aug 19, 2015 20:56
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baka kaba posted:It's ironic that you call the Pi limited like the BBC, after advocating kids learning Logo (a BBC staple) instead of all the cool, engaging stuff the Pi and its ecosystem is allowing them to do Logo wasn't invented for the BBC Micro, and it was solely brought up as an example of a computer science thing that even a completely untrained in computers teacher can handle, and use on the existing computers for less money. Normal computers have an even "cooler" and "more engaging" ecosystem of things you can do with them, especially for elementary school students learning computer science, which you appear to be stuck on.
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Aug 19, 2015 21:01
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BattleMaster posted:But CS doesn't even necessitate actually touching a computer. Are you thinking of engineering? No, it doesn't. But Applied Computer Science does. https://en.wikipedia.org/wiki/Outline_of_computer_science That's like saying I don't need a Doctorate Degree to be a Surgeon. 
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Aug 19, 2015 21:11
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The problem with "garbage tier" x86 stuff is that it usually eats a lot more power than something like a Pi, and in many countries (including the one I live in) energy is so expensive that it is a very real consideration for something you want to run 24/7. That's the real reason why it's barely worth it anymore to recycle old computers into homeservers. The computer might have been (almost) free - but the electricity bill they will run up in sometimes, two years (and yeah, I'd like a fire-and-forget sever live longer than that without permanently having to fiddle with it) will get you something newer, better and less wasteful. While ARM computers might be relatively weak for what they cost, you usually won't get that processing power-to-watts ratio with x86. If one isn't enough In doubt it *might* even be cheaper to just run two ARMs instead of one more powerful "conventional" x86. (even for platforms that were meant to be primarily energy saving and have very impressive idle numbers, a computer usually doesn't just sit there and idles all the time, because if it would, you probably wouldn't need it running. Then also you still have to add the peripherals and their various inefficiencies. The real energy consumption recorded over time under real circumstances is often significantly higher from what you'd take from the advertisement blurb, especially because it's easy for mainboard- and power supply manufacturers to skimp on the power infrastructure in hardware revisions without anyone really noticing) I was very wary regarding the Pi 2 after I was disappointed with just how slow and borderline useless the original Pi was doing normal computer stuff, but I'm pretty happy with the Pi 2 as headless server fulfilling several functions for me, including music- and video streaming. The quadcore setup really helps with server roles. The trick to get the most of it is running it as barebones as possible and writing your own stuff instead of relying too much on sometimes bloated solutions for some things. (If you're a newcomer to Linux, don't always believe the widespread and often repeated myth Linux software is inherently "more lightweight". It can be just as bloated and useless as the worst windows-targeted stuff) When my Pi is very busy, it sits around ~1.4-1.6 load average with about maybe 30-40% RAM in use. That's at stock speeds. I can live very well with that. Of course it always depends on what you need. Also whoever thinks something like external wiring and making actual LEDs blink pretty colors is the same than having the same kind of thing abstracted on a computer screen obviously never did anything with bored and testy kids around afternoon after a long school day in any capacity. That being said, you really can do all of this with a normal computer. I've been using parallel ports as GPIO before I even heard the expression "GPIO". Granted, this is probably a mess to do with with modern computers and operating systems but I'm sure you could come up with similar fiddling solutions via USB and some microcontroller. The question is if that'd be cheaper and easier than just buying a Pi and fall back on all the documentation that's there. It's probably easier and a lot less time consuming and demanding for a school to just buy a bunch of Pis. It doesn't even really matter if a computer can do it in that case. Regardless, it is a pity that modern computers are just so closed up black boxes where it's very hard to follow what's going on. I would have a lot of a harder time with "learning computers" (not only clicking on some symbols, actually understanding how it works on a lower level) if my first computer would've been an i5 instead of an Amiga.
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Aug 19, 2015 22:23
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Police Automaton posted:The problem with "garbage tier" x86 stuff is that it usually eats a lot more power than something like a Pi, and in many countries (including the one I live in) energy is so expensive that it is a very real consideration for something you want to run 24/7. That's the real reason why it's barely worth it anymore to recycle old computers into homeservers. The computer might have been (almost) free - but the electricity bill they will run up in sometimes, two years (and yeah, I'd like a fire-and-forget sever live longer than that without permanently having to fiddle with it) will get you something newer, better and less wasteful. My Zotac ZBOX BI320 with a 2957U pulls 5W at idle and 15W at load, measured at the wall. Like OK I guess that's not 3W like the Pi2, but it's pretty damned low and the whole thing is probably eclipsed by my girlfriend's crippling inability to turn off the lights. An Intel J1900 system pulls about 23W idle and 32W at full load with GPU. At my current electricity rates ($0.16/KWh) a constant 15W of electricity works out to $1.73 per month. Even if you pay double that, if you can't afford $3.50 per month in electric you probably shouldn't be buying even a $35 computer. I agree, it's totally worth replacing older servers with newer low-power ones. It's good that the Pi2 worked out for you, I tried a Pi1, it was so useless and I had so many problems that I pretty much burned out on Pis forever. I wasn't even satisfied with it as an OpenELEC system. Went with the low-power x86 systems and haven't looked back.  Police Automaton posted:I was very wary regarding the Pi 2 after I was disappointed with just how slow and borderline useless the original Pi was doing normal computer stuff, but I'm pretty happy with the Pi 2 as headless server fulfilling several functions for me, including music- and video streaming. The quadcore setup really helps with server roles. The trick to get the most of it is running it as barebones as possible and writing your own stuff instead of relying too much on sometimes bloated solutions for some things. (If you're a newcomer to Linux, don't always believe the widespread and often repeated myth Linux software is inherently "more lightweight". It can be just as bloated and useless as the worst windows-targeted stuff) When my Pi is very busy, it sits around ~1.4-1.6 load average with about maybe 30-40% RAM in use. That's at stock speeds. I can live very well with that. Of course it always depends on what you need. In particular you probably want to avoid anything written in Python. It's never a fantastic performer, but it just chugs on the Pi. Unfortunately, everything is written in Python. Paul MaudDib fucked around with this message at 23:54 on Aug 19, 2015 |
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Aug 19, 2015 23:44
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The Raspberry Pi A+ uses 178ma with an Edimax wifi dongle/nub with an active SSH connection  Actually my new two Samsung 18650s just arrived for my robotics project and I picked the Raspberry Pi A+ as the sweet spot between a) reliable linux/hardware support distribution (RPIO ftw) b) price ($20 shipped) c) form factor (barely larger than an Arduino and d) small enough power consumption that you can run it off of a solar panel the size of a playing card in direct sunlight Paul MaudDib posted:Can you give a specific example? Yeah I was curious what the onboard micro controller is capable of. I guess as an example off the top of my head, if you wanted to create a slow scan TV signal from a live webcam video feed at say 2000hz to an SPI device, you would run in to issues, for example 3Ghz PC producing 2000hz signal -> USB Connection @ 500hz -> Bus Pirate @ 40 Mhz -> SPI device @ (ok speed) Either you're going to have to introduce some latency by sending 4 "frames" every USB frame, or you're going to drop 75% of the signal. The PC and the Bus Pirate are totally good, but the mere 500hz bus speed of the USB isn't going to cut it for anything realtime-y Although as I go fact checking my post it sort of sounds like USB polling speed is independent of the USB spec and seems like it's OS and peripheral-device dependent. So maybe you could push USB to 2000 or even 2500-3000mhz. And digging in to the SPI wikipedia page I'm reading things like "100 Mega-samples/second" so maybe that's how you would push a 2000hz signal out to a device over a 500hz bus, you'd just have what, ~.75ms latency?
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Aug 20, 2015 01:14
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Paul MaudDib posted:In particular you probably want to avoid anything written in Python. It's never a fantastic performer, but it just chugs on the Pi. At least if you're writing new code it can be in C. One of the benefits of using Linux, every distro will have gcc and make. BattleMaster fucked around with this message at 02:28 on Aug 20, 2015 |
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Aug 20, 2015 02:25
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Raspberry Pi running Seafile report:
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Aug 20, 2015 22:00
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What's the advantage over using something like Google drive or whatever?
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Aug 21, 2015 05:34
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Skarsnik posted:What's the advantage over using something like Google drive or whatever? Privacy.
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Aug 21, 2015 15:12
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Skarsnik posted:What's the advantage over using something like Google drive or whatever? Generally, or personally? If generally, what eightysixed said, privacy, personal control over your data, a secondary or tertiary means of file duplication and access. Personally, it's fun, an entree into basic Linux server management, and I can use the knowledge gained to set up a HIPAA compliant file server for the company I work for (not with Pis, of course). Similar reasons to why you'd build your own PC or change your own oil rather than pay a company do it for you.
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Aug 21, 2015 22:30
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What software could I use to stream videos and whatnot to a Roku through the Roku's media streaming app? I guess I can study up on how to use minidlna? Mind you, I don't want to use the Pi itself to output the video, just stream it to the Roku. I figure that's a lower impact task that's more suited to the Pi, and it's on all day anyhow, may as well get some extra use out of it.
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Aug 21, 2015 22:58
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Installing complex products in Linux is great fun (for me, at least) and you learn a TON about the inner workings of the OS, command line, install prices and more. It took me almost a week but I got Ox App Suite (new name for open exchange, it's like open source gmail with a Seafile drive thing) installed along with the dovecot, MySQL and apache stuff, along with making it play nice in a seperate subdomian with the other web based apps. And then all the crazy domain stuff, mx records and not getting flagged as spam by gmail (which is way harder than it sounds). As they say in IT, you learn the most when things go wrong. Getting everything working happy together can sometimes feel like a goddamn miracle.
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Aug 21, 2015 23:06
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Hadlock posted:Installing complex products in Linux is great fun (for me, at least) and you learn a TON about the inner workings of the OS, command line, install prices and more. A while back I installed Lubuntu on a bottom-tier craptop (Compaq CQ56-115DX with an AMD V140 single-core CPU), and I had a blast doing that too. It was totally useless as configured and on Windows, but after I swapped in an SSD and installed Lubuntu it was very acceptable for web browsing, office, programming, etc. One of the nice things about Linux is there's no inexplicable behavior, there's a very straightforward mechanism for how the system implements every piece of its functionality and when it's not working right you can start tracing through it and find the problem. Often there are more problems than I would prefer, but that's the nature of the beast. I also learned to stay the gently caress away from x.10 releases and to be wary of even doing dist-upgrade to another LTS release. It was about a 50/50 whether at least one major subsystem would need to be debugged after a dist-upgrade. I'd probably rather use etckeeper and reinstall. According to a Whetstone benchmark that V140 was about 4x as powerful as a Raspberry Pi 1. I hadn't compared them directly before but it's kind of an interesting datapoint that I found that laptop OK even driving a (lightweight) window manager but ragequit the Pi even on basic server stuff. I think the use of USB as a system bus probably significantly impairs the user experience - there's no way a SD card can compete with the throughput or latency of a SSD, and the USB bus has to be crippling that even further. I actually bet a Pi with a real SATA channel on it (eg Jetson TK1 or Banana Pi) would be pretty OK as a lightweight desktop PC. It would certainly be a lot more stable without the SD card burnout crap. Paul MaudDib fucked around with this message at 00:07 on Aug 22, 2015 |
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Aug 21, 2015 23:35
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I've been reading up on implementing GPIO on the Pi and apparently doing very simple tasks like creating a square wave, it's capable of up to nearly 60mhz on a single pin in non-realtime Linux. SATA supports a mode at 37.5mhz so I wonder if you could implement native SATA on the Pi over GPIO in C, thus bypassing the shared USB on chip logic. poo poo, someone's probably already done it, USB drive read write speed is the biggest real world flaw on the device and that seems like a fairly easy solution. You would need a custom cable though. You could probably write out the data to an SD card issuing I2C mode on the dedicated I2C bus, buffering in memory, all but removing the system SD card from the loop. Hadlock fucked around with this message at 00:46 on Aug 22, 2015 |
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Aug 22, 2015 00:42
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Hadlock posted:I've been reading up on implementing GPIO on the Pi and apparently doing very simple tasks like creating a square wave, it's capable of up to nearly 60mhz on a single pin in non-realtime Linux. SATA supports a mode at 37.5mhz so I wonder if you could implement native SATA on the Pi over GPIO in C, thus bypassing the shared USB on chip logic. poo poo, someone's probably already done it, USB drive read write speed is the biggest real world flaw on the device and that seems like a fairly easy solution. You would need a custom cable though. How stable is the waveform under load? I'd imagine a CPU implementation of SATA could be limited by that especially if it is writing during any kind of processor intensive task. Though there is that one hack for doing PWM for servos using DMA that seems pretty stable so someone clever enough could make it happen.
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Aug 22, 2015 03:42
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doctorfrog posted:Generally, or personally? That's fair enough, I'm always looking for new stuff to try out on mine, so I might give it a go The privacy stuff isn't really a draw for me, but a new project always is
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Aug 22, 2015 07:01
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Hadlock posted:Intel CPUs do have I2C, SPi and GPIO, but it's mostly not break-out-able That's pretty much what the Intel Edison is. The Intel IoT folks have their mraa library for GPIO/I2C/etc. configured for use on Edison, Gallileo, and Raspberry Pi, and I think other boards are picking it up too. (I filed a bunch of bugs a few months back about making it more modular…)
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Aug 22, 2015 08:58
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I got my Pi talking with my PS3 controller and set up a sort of slolem course for it in my living room. All this python crap is super simple it all just goes together like legos and there's just some glue code involved. The script that runs this thing is barely 170 lines and a full 30 of those are elif statements handling nonessential button presses. https://www.youtube.com/watch?v=hzreSw6Uyds I have better voltage step down and motor controllers on the way. Going full forward to full reverse is enough to cause a big enough voltage drop to the Pi to knock it out. I have 2x18650 2500mAh samsung batteries which have powered this thing for a couple of hours, a couple of laps around the house and chasing the cats to and fro with about 50% useful charge left. Next step(s) are to mount the webcam, get streaming video running, and further down the road computer vision and linking that up with the nav system and proximity (wall) detector. Hadlock posted:Does anyone know how/why GPIO 5 would be HIGH on boot but GPIO12 is LOW? Kind of annoying that my robot likes to spin in clockwise circles (takes the whole "loading" icon to a whole 'nother level...) until the initial python script boots and apparently starting the python prompt resets that pin. It would be nice if I could force the GPIO LOW to start... If anyone else runs in to this issue, the reason is because Broadcom starts some pins HIGH and some LOW by default. This is detailed on page 106 or so here https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2835/BCM2835-ARM-Peripherals.pdf ickna posted:How stable is the waveform under load? I'd imagine a CPU implementation of SATA could be limited by that especially if it is writing during any kind of processor intensive task. Though there is that one hack for doing PWM for servos using DMA that seems pretty stable so someone clever enough could make it happen. It's probably crap. I wouldn't trust my data with one, that's for sure. It would be an interesting experiment though. The Pi foundation does distribute a RISC OS with it, which is a real time OS and probably would be totally acceptable for that sort of thing. But yeah you're right it's not really suited for the task at hand in Linux. I am doing software PWM for 2x200hz pins, but it's just for DC motor control so it can be super sloppy and not impact anything for me. lossless data on the other hand is not so forgiving.
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Aug 22, 2015 09:00
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Nintendo Kid posted:Logo wasn't invented for the BBC Micro, and it was solely brought up as an example of a computer science thing that even a completely untrained in computers teacher can handle, and use on the existing computers for less money. Also, Logo actually has a pretty good track record when it comes to teaching the basic concepts of computer science in ways that elementary students find interesting and that will lead to better learning outcomes in their subsequent education. Seymour Papert is required reading for anyone interested in computing in education.
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Aug 22, 2015 09:06
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doctorfrog posted:What software could I use to stream videos and whatnot to a Roku through the Roku's media streaming app? I guess I can study up on how to use minidlna? As a first step (perhaps a bigger one than necessary), I installed OSMC, and it's pretty slick for what it is. It has a pretty smart installer that asks for your wireless config up front, and gives you the option to boot from an SD and then run from a USB drive (dual-boot OSMC and RetroPie, maybe?). It'll play SD media just grand and streams to a Roku handily enough for the HD stuff. Runs the Pi pretty hot, though. The USB drives (which it detects automatically and allows you to play media on there with no problem) were like touching the side of a cup of coffee about 20 minutes old. It's weird, with seemingly well-crafted OS distributions like this it seems that people want the Pi to be something that it clearly isn't designed for as a long-term solution, and I wonder if/when the Pi group is going to respond. Or even if they can. If the board were $60-100, would there even be this kind of community energy behind it?
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Aug 25, 2015 02:18
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doctorfrog posted:What software could I use to stream videos and whatnot to a Roku through the Roku's media streaming app? I guess I can study up on how to use minidlna? My Roku HDMI stick saw it and played stuff off of it no problem. The only issue I've had is that miniDLNA won't start up if I have to power cycle my Pi, but I've chalked that up to my own Linux incompetence. Fortunately it stays running once you manually start the service so I haven't spent all that much time figuring out what I did wrong.
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Aug 25, 2015 04:18
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Karthe posted:This is the guide I used to get minidlna up and running on my Pi 1 B+: http://bbrks.me/rpi-minidlna-media-server/ Thanks, this should be a bit less overkill and hopefully will fit just fine with RetroPie (which uses Arch instead of Debian?). I'm starting to like the get-your-hands-dirty approach to getting these things to work, because when the GUI stuff stops working, you're just helpless. The more command-line stuff I do, the easier it is to puzzle things out when they don't work. edit: works perfectly. doctorfrog fucked around with this message at 05:45 on Aug 25, 2015 |
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Aug 25, 2015 04:58
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I'm trying to cook up some sort of alarm system for my garage, which has no power (and is infeasible to run power to). I was thinking of some sort of light beam or maybe magnetic sensor on the door, hooked up to a Raspberry Pi which also controls a siren of some kind. The reason I'm looking at a Pi for this is because of the ease of using a usb wifi/bluetooth dongle to connect to the Pi to enable/disable the alarm. The only experience I've had with electronics was some soldering to install a new PCB in an arcade stick, so I'm really out of my depth here. I do have experience writing software though. The first problem is power, how feasible is a battery powered Model A+? Could I run the Pi, the sensor and the wifi/bluetooth dongle off of rechargable batteries for at least say, 10 hours? Second problem is the siren, and it's related to the first I guess. The sort of sirens I'm after are 12v, the Pi takes 5v. With my lack of knowledge I don't know how I can run these off of a single power source. The siren itself won't need to run for long. Lastly, is the Pi even the best option for this? Would an Arduino with bluetooth or wifi be more suited? I didn't see any general electronics thread in the first 5 pages so I hope I'm in the right place.
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Aug 29, 2015 14:45
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