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Raspberry Pi + LCDuino system

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Raspberry Pi + LCDuino system

Postby linux-works » September 11th, 2012, 5:58 pm

today, I can happily report that the first demo version of the two systems is working.

the raspberry pi is the ethernet tcp/ip webserver front-end (also means its the android/iphone way in) and it talks 'volume control language' over a serial connection to the lcduino. the pi system has an onboard hardware uart (/dev/ttyAMA0) and the arduino has one, too (2nd and 3rd pins on the 6pin ftdi vertical 'download' header on the lcduino).

here's a simple level converter that works, is super cheap, and btw, did I say that it works? ;)

Image

a simple cd4050 cmos chip that is half a dollar or less. the schematic comes from this link:

http://www.andremiller.net/content/rasp ... -gpio-uart

a 'shield' is made from perf board and a 26pin (strange but buyable) dual row .1" spaced IDC style socket. there is no support for shields, no screw holes or anything, so I did my best to get the one single chip to line-up on an 'available' (lol) riser connector that I'll never use or care about. I put that cmos chip *just* so, and then worried about the rest afterwards.

Image

wire layout is simple:

Image

the Pi board provides 3.3v via pin1 (square index pin on the Pi pcb; on my board, its the only blue wire there. (btw, don't ever cut the blue wire!) ;)

the green wire is the gnd connection.

black and white are tx and rx (check the schematic for which is which).

the red molex connector takes the tx, rx and gnd offboard and onto the arduino system. there, you use the usual colors that the ftdi cable uses (except my green is ground; ftdi 'official' gnd is black/brown).

this assumes you power the lcduino from a nice 5v supply and you have given power to the Pi via its micro-usb connector or some other way.

that's all the hardware hacking needed! just that one cd4050 chip, some wiring and sockets and software. yeah, it needs some software on the 'pc' side ;) more on that, later.
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Re: Raspberry Pi + LCDuino system

Postby MASantos » September 12th, 2012, 8:49 am

Might this be the start of a linux/amb media server? 8-)

Seriously now, how hard would it be to have the pi managing an hard drive and doing media server functions with control of the arduino for volume and I/o?
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Re: Raspberry Pi + LCDuino system

Postby linux-works » September 12th, 2012, 9:18 am

its a lousy NAS. reason: no sata ports!

a future one might have them, but this one is not ready for that.

I have been working on my own NAS codebase, in fact, but pretty informally. I've been calling it bryNAS ;)

it is linux based (voyage), can run from a usb stick (no o/s drive) or a regular ssd and does the usual samba/nfs file export stuff.

one thing I recently found that interests me is the 'filterFS'. in a nutshell, you can use linux FUSE layer to run a process that acts like a filesystem. that filesystem can show ONLY the files that match wildcards that you hand it. so, if you had a mixed directory tree with, say, flac files and mp3 files and you wanted to see only the flac files, you'd select *.flac as the filter, then mount or drag a tree of files to your music player and ONLY those files would appear on the NAS server. the others would just be hidden from the filter output (if you did a DIR or ls, you'd only see the files that fit the wildcard). and you can change it anytime you want.

maybe you save movies in the same NAS. maybe also software installables/kits. with a master wildcard switch, you could hide a lot of the 'junk' so that when you want to select a whole tree or subtree, only the 'right' files play.

I'm thinking of putting that on my bryNAS image. I've tested it and it does seem to work.

if there's enough interest, I could tar up my NAS usb stick image and let people play with it. its mostly just regular linux, but its setup to boot from a simple usb thumbdrive, so it does not take up any valuable sata ports.

for my testing, I'm using fanless atom cpus or amd e350 cpus. for a nas, you still want some power in there (large files can take forever to copy across and backup). I hesitate to go much lower in power than the atom class chips.

another major feature I plan to add to that is smarter spinup/down of drives and smart file replication (NOT raid, as I hate having all drives spin just to access one file on a home system). I'm designing some ways to spin down the drives that aren't needed during a music or movie 'play event' and keep this really low power and low noise. regular NAS boxes don't really do anything smart; they just use the auto spin feature that some drives have. that's often not enough or not even working and so I'm taking a different approach (using mount/unmount commands and relays to literally spin the unused drives down).
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Re: Raspberry Pi + LCDuino system

Postby linux-works » September 15th, 2012, 4:23 pm

here's a really good view of how to do the level conversion:

Image

link:

http://picasaweb.google.com/lh/photo/j- ... dlEXo9TSiA
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