RaspberryPi + LinkMeter blue sky discussion


 
Yeah I saw that too. I don't use Raspbian though, I use a custom OpenWrt build which is already using hardware floating point (although with a softfp-abi). Rasbian needs hard float so bad because they're running a gigantic Debian linux system with a GUI. LinkMeter doesn't get much of a boost to performance because it isn't as taxing on the system.
 
I was busy (in life) and mad at the Pi so I hadn't got around to returning it. I should have because Element14/Newark immediately shipped a new one at the same time they gave me the RMA number.

Glad things are going well besides you frying your board.
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Bad news is the first boards I made aren't going to work without cutting traces because there's no way to keep CE0 asserted between SPI transactions.
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What does this mean exactly?

I am moving back to NC in three weeks so I probably won't be around much but I was thinking of redesigning the board for an SMD version...just for fun. I want to make sure you have a fully working schematic before I do that.
 
Originally posted by Dave S (GeoDave):
What does this mean exactly?

I am moving back to NC in three weeks so I probably won't be around much but I was thinking of redesigning the board for an SMD version...just for fun. I want to make sure you have a fully working schematic before I do that.
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I had wired the Pi's hardware chip select, CE0 to the /RESET pin on the ATmega thinking it would be able to generate the requisite signals to put the AVR into programming mode. However, the SPI kernel driver always de-asserts CE0 at the end of each SPI "message", if there's no other message waiting to be sent. To program the AVR you have to hold the /RESET line low the whole time so CE0 was unsuitable for this application.

The cutting traces I was referring to was on the HeaterMeterPi board though.

Whatever you do don't use the schematic in github labeled "DO NOT BUILD". It has a critical flaw in that the 5V switching regulator's pins are connected backwards (actually they're built backwards) which will connect your Pi up to 12V. I should have the updated version up this week. I've also decided to go with a different board layout which
means the SD card will be inside the enclosure rather than having to cut a slot for it. I would call it nearly the minimal PCB footprint that can enclose the Pi with its SD card as well as have the probe jacks onboard.


The final exterior dimensions will be 4.1" wide x 3.2" deep, versus the 3.3x4.1 of my first design. The board is also 18% smaller so it will only cost $11.62/ea.
 
Originally posted by Bryan Mayland:
The final exterior dimensions will be 4.1" wide x 3.2" deep, versus the 3.3x4.1 of my first design. The board is also 18% smaller so it will only cost $11.62/ea.
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Nice, that looks pretty tidy. Have you put any thought yet into enclosures for this stacked board design? The OCD side of me desperately wants to be able to stack them all vertically. I'm wondering if the board was reversed so that it stacked on top of the Pi, and the LCD was then attached via a ribbon cable or something if you could mount the LCD on the side of a rectangular enclosure (with the button out the top). Know what I mean?

Cutting the LCD hole in my linksys was a pain in the butt, it would be awesome if some enterprising soul did up plans to get an enclosure laser cut or something.
 
I really wanted it all to stack directly on top of the Pi as well. The problem was that there wasn't enough space in the same footprint to fit all the components on the underside. If the components are on the top of the board, then the button isn't tall enough, and the LCD still had to be mounted elsewhere. There was also the issue that the Pi has no mounting holes so it would float inside the case.

Putting the LCD on the front is actually a really smart idea... dangit. You wouldn't even have to use a ribbon cable because you could put the LCD connector on the front edge and use a right angle pinheader to attach it directly. It still doesn't solve the button problem, it would be cooler if it were on the front. EDIT: I'm not sure there's enough edge space available to have the power, blower, and 4 probe jacks if built stacking directly over the Pi.

I don't know what I'm going to do for a case though, the whole shebang is over an inch / inch.5 high, at least 3.2" deep and needs to be exactly 4.1" wide for the connectors to poke through properly.

EDIT: The place I was thinking of that makes custom cases is Ponoko. I've seen some really nice stuff that isn't too expensive ($20 for a small enclosure) and can be made any size. I have no clue how to build something with them though.
 
Originally posted by Bryan Mayland:
Putting the LCD on the front is actually a really smart idea... dangit. You wouldn't even have to use a ribbon cable because you could put the LCD connector on the front edge and use a right angle pinheader to attach it directly. It still doesn't solve the button problem, it would be cooler if it were on the front. EDIT: I'm not sure there's enough edge space available to have the power, blower, and 4 probe jacks if built stacking directly over the Pi.
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Yeah, my ideal design would put the LCD and button on the front, and the probe jacks + power on the back.

I built one of those Icetube clocks that came with a laser cut plexi case that was sort of neat (which I promptly broke putting together.)

I've got friends with CNC mills, vinyl cutters, you name it, but none with cool lasers.
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Personally, a cool case "makes" projects like this, so I'd totally be down with splurging on a snazzy case (within reason).

I'm not planning on using my Pi for stuff other than the HM at this point, but it would be pretty cool if there was some type of "pass through" functionality later on to be able to interface with the LCD on the linux side of things. I can see that being useful.
 
I considered using one of those marine car stereo head unit waterproof cases:

http://www.amazon.com/s/ref=nb...ywords=marine+gimbal

They are pretty cheap, and you could leave it out in the weather. You'd still need a custom panel to mount in the front of it, but there would be plenty of room for probe pigtails and power out the back.

FYI, Newark (Element 14) states 29 day lead time and is accepting rPi orders... I know that was stated above, but they were not taking orders when I tried. I'm a bit angry since I "Registered my interest" with them the day the rPi started accepting orders and I never heard anything about them opening orders back up
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Just use one of those nice lego cases I see people make :)

I was wondering. Do these little Pi units generate much heat? How much ventliation would they need, etc?

I ordered two of these little units today. 6-12 week delivery time :-(
 
Yeah I scratched my head at the Ponoko site for a long time when I first heard of them because I didn't understand their pricing or how things were actually made. I think I've got it figured out now though, you buy a sheet of P1 P2 or P3 sized material, and then pay for how long the laser runs. A sheet of 3mm P1 (181mm x 181mm) matte black acrylic is $4.18 and the laser appears to run a "few minutes" to cut out a basic assembleable cube with an LCD cutout and some holes. So you're looking at about $5 in materials, $6 in laser, and $5 shipping. Not terrible at all but you're limited to a pretty basic design. You can get 3D prints but they say large flat pieces come out warped so I think that's out. I was thinking of making a design in hardboard then sanding it a bit and painting it.

There's some good pictures at at this forum for Mutable Instruments.
 
Originally posted by Dennis C:
I was wondering. Do these little Pi units generate much heat? How much ventliation would they need, etc?
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Not much. They get warm to the touch but less than my Linksys's CPU. I think they can run enclosed no problem. They're cellphone CPUs after all.
 
Not much. They get warm to the touch but less than my Linksys's CPU. I think they can run enclosed no problem. They're cellphone CPUs after all.
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Figured so. I know the iPhone gave me a message that the phone was running hot and I couldn't use it until it cooled off. I had it directly in the Sun when I got this message.
 
ured so. I know the iPhone gave me a message that the phone was running hot and I couldn't use it until it cooled off.
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A bit off topic, but I believe heat issues in phones are typically due to high discharge rates of the battery. That was always the problem on my phone at least. I'd be more worried about the LM7805 LDO Regulators, since they turn excess voltage into heat. Even so, they should be fine in a case.

The rPi is said to be good for at least 0-70c (32-158F).
 
The thought of case fabrication get me intregued so I took a closer look at Ponoko.

Don't know if anyone has seen the following page on how to fabricate 'snug' joints... I could imagine using this type of aproach to build a box. Blog Post

Has anyone started to create a 3d sketch of a case?
 
Originally posted by N Waring:
The thought of case fabrication get me intregued so I took a closer look at Ponoko.

Don't know if anyone has seen the following page on how to fabricate 'snug' joints... I could imagine using this type of aproach to build a box. Blog Post

Has anyone started to create a 3d sketch of a case?
Click to expand...

The icetube case uses a dovetail sort of design I thought was sort of clever (but it's not durable enough for a HM imo).

http://www.ladyada.net/make/icetube/case.html
 
The icetube case uses a dovetail sort of design I thought was sort of clever (but it's not durable enough for a HM imo).
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mmm... I thought that it may be just a bit fiddly to have to use multiple screws and bolts to join it together. I guessed on 20 screws needed to create a 'stable' box:
2 for each of the 4 edges on the top and bottom (16 in total)
4 to join the sides together

My other thought was to use the dovetail approach to join the parts together and then pass a long bolt (60mm?) through from top to bottom on each of the 4 corners.

I did also see the following case which I thought looked nice and simple... but it doesn't look particularly customisable
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Bryan, is there any thought on keeping the two parts (HM & Pi) separate with a some type on 'connection' between two cases?
 
Was just reading about a new case. Just thought I'd post the info here.

not much exact details but here is what I seen on the website.

pibow.com

Expansion

After you've got your Pibow, that's just the start, because we'll be releasing a series of expansion layers that work with the Pibow.

Camera Module?

Want to mount the Official Raspberry Pi Camera Expansion on your Pibow? We'll have a layer for that, that you can buy and use with your existing case. No need to buy a whole new case!

VESA Mount?

Want to stick your Raspberry Pi on a TV, we've planned ahead for that! You'll be able to simply replace the base layer with one that fits on a series of standard VESA mounts (although you won't be able to see the full majesty of your Pibow then)

Tinkering?

Want to work with a breadboard, or other electronics and have them attach to the Pibow? We can do that. More plates will appear offering modular expansion around the Pibow so you can keep projects tidy and easy to understand.

Been Mean to your Pibow?

No problem. The Pibow is made from durable, shatter-proof acrylic, but part of the fun of the Raspberry Pi is doing things that are interesting enough to break bits.

We'll make sure you don't have to buy a whole new case, just replace the broken bit. Much better!
 
Originally posted by N Waring:
Bryan, is there any thought on keeping the two parts (HM & Pi) separate with a some type on 'connection' between two cases?
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Not really. The idea is that you want to have to bring as few parts as possible to the grill. One could theoretically bring the Pi expansion port to the edge of its case and you can use a parallel cable to connect it to the HeaterMeter (at least 9 wires). No Pi cases I've seen have any access to the expansion port though.

I think it is a little early to design a case, other than just general ideas, because I'm not entirely sure what the exterior dimensions are going to be.

The standard sort of dovetail would probably be fine-- the top could be glued to the four sides, and then use that strange nut/bolt thing to hold the bottom on.
 
How about fiberglass a case and bondo for the finishing touches. Fiberglassing is pretty easy.

you could make a case out of foam then fiber over it and then take acetone to melt the foam out and you have a nice little case. Of course there a few more steps involved but its not hard at all.

Edit: Actualy I might as well make a case for my heatermeter build out of fiberglass and I will post the results when its finished. I have some fiberglass from doing a trunk lid cover for car and some foam, I can even fiber in all the mounting hardware into the case for probes ect.....

Just throwing putting my 2 cents in this discussion, lol.

I thinking really hard about getting a PI just want to wait until its little more polished before I get more parts that I can brick
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Rage! The free version of EAGLE only lets me place components up to the 4.0" mark and I just need 4.1" to place the probe jacks close enough to the edge of the board. I've managed to trick it by making a fake component with the pads set back 0.1", placing it, then replacing the component with the right one. As long as I never have to nudge the component it should be ok, right?
 
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