Fanless "embeded" linux computers.

[owenhamburg]

I have a wireless router (wgt634u) running Debian (A form of Linux), and a USB sound card (Creative sound blaster) which with a USB hub and USB hard drive I used to use as a NFS server for sound control I used a mpd server. With this I could play music, in the bedroom and no fans. It was not quiet able to cope with my NAS requirements so it got replaced. My router was seriously underpowered compared to a PC, but could still upscale sound to 48Khz (Sound balaster required this) without dropping with only this CPU

cpu model : Broadcom BCM3302 V0.7
BogoMIPS : 198.65

For comparison my low power AMD Athlon(tm) Dual Core Processor 4850e has

bogomips : 2009.13

In each core, and that's a 40 Euro CPU!

As an interface I had an old USB based palm computer which I wrote a simple MDP UI, but since the palm development kits for OS4 (my palm) where no longer supported in later Debian releases I gave up on this project. (Some one else made one for Palm > OS5)

If I was to do the project today, and to provide a media HUB (unfortunately this came out after I had bought an Intel atom box I failed to completely silence) I would use a new ARM embedded board to replace the hacking with an old wireless router.

Marvell: Kirkwood Developer Resources

This looks like it could do all my NAS requirements and be a good HiFi Source.

I must admit I am tempted but I replaced my wireless router solution with a MythTV box (with a fan) and a Internet radio, but the idea still appeals and I thought I would mention some thing I found that might appeal to some one wanting to do this today as people seem to talk a lot about AMD/Intel solutions. Radio 4 (and the BBC's use of real audio) was the main reason to start the project but since realaudio is proprietary format I could not wake up to BBC radio 4 in Germany so all in all the Internet radio is irreplaceable, though the Intel atom box may well be replaced when chips like the kirkwood start appearing in Netbooks.

Thought you guys might be interested, and maybe share your embeded computer solutions.

[dangus]

It may be more practical to use an off-the-shelf media player. Some of them run Linux and are hackable. They come with stuff like IR remote control, TV and audio out (including S/PDIF), as well as network support. They've got powerful hardware video decoding; they'll play Blu-ray quality files at 1080p. Examples are the Western Digital WD TV, and the Xtreamer. The price is the best part: not much over $100. The original WD TV just played media off USB devices, but it's been hacked to add network support. A new version of the WD TV is supposed to have an ethernet jack.

I'm still "planning" to build some kind of media player, probably in the case of an old CD player as a trial, then in a gutted vintage car-phone case as a truck player. Maybe in a salvaged industrial cabinet as a workshop player.

For a CPU, I've a choice of several Pentium and Geode-based embedded boards, in "biscuit" to 1/2 ISA to PC104 form factors. I say "planning" because this has been going on a while... better hardware keeps coming along, and I've worn out several MP3 CD players in the meantime.

I'd start with a DOS-based player, mpxplay, since it handles every audio format, supports alphanumeric LCD displays, and resumes. DOS or a DOS-only Windoze should boot quickly, and fit on a CF card or "Disk-on-chip" which some of the boards support.

Display would be 2x40 alphanumeric LCD display - probably - although I've acquired a couple of small LCD video monitors, which could work if any of the boards include TV out, or if the onboard VGA can be persuaded to output TV-rate RGB.

Another issue is audio out; one biscuit PC has a PCI slot, but that's a pentium 1 class board. If an SB16 is good enough, that would work with the 1/2 ISA CPU and a passive backplane. A few boards have on-board audio, but I'd sooner use USB or PCMCIA.

I ordered a couple of cheap USB sound dongles off eBay and wasn't thrilled with the quality; some actually sounded like kazoos. One I picked up at Radio Shack used a CM102S, sounded OK, and has a pin to add S/PDIF out. So, that could be the one for CD case player, and use on-board sound for the shop player.

On the other hand, hot-gluing a 5" car LCD monitor to the side of a WD TV would be a lot less work and decisions.

[owenhamburg]

Hi Dangus,

Great ideas, I can see you have thought about this a lot.

The hot glue and 5" LCD monitor seems like a very nice option with a off the shelf media player. They have only opened part of the firmware for the Xstreamer and WD TD, and remembering my experiences with the wgt634u, I would avoid a system where its hard to build a Linux kernel my self.

I cant help feeling for a fanless system embedded devices are the way to go, both your suggestions and mine require ~30 W power supplies so heat is not an issue as it would be with PC's.

Maybe the next generation of Netbooks when they come out will also provide some interesting options, Smartbook - Wikipedia, the free encyclopedia for a less effort solution.

[nmiljac]

I would forget about any of x86 based designs. Almost anything else will run on much less power and probably sound better, especially ARM based boards that have linear regs powering the CPU. Most of them have an on-chip serial digital interface that can put out I2S or any of serial formats.
You don't need much processing power - my commercial design runs on a 200 MHz ARM9 based processor with 64 MB of RAM and 512 MB FLASH and decodes FLAC without any problem.
30W is more than enough to power it. (and yes, it's Linux)

[nyc_paramedic]

Originally Posted by nmiljac

I would forget about any of x86 based designs. Almost anything else will run on much less power and probably sound better, especially ARM based boards that have linear regs powering the CPU. Most of them have an on-chip serial digital interface that can put out I2S or any of serial formats.
You don't need much processing power - my commercial design runs on a 200 MHz ARM9 based processor with 64 MB of RAM and 512 MB FLASH and decodes FLAC without any problem.
30W is more than enough to power it. (and yes, it's Linux)

Not true. You can use a PC Engines x86 Geode based ALIX board and still come under 4 watts total power draw.

Quick specs for an Alix 2d2:

CPU: 500 MHz AMD Geode LX800
• DRAM: 256 MB DDR DRAM
• Storage: CompactFlash socket, 44 pin IDE header
• Power: DC jack or passive POE, min. 7V to max. 20V
• Three front panel LEDs, pushbutton
• Expansion: 2 miniPCI slots, LPC bus
• Connectivity: 2 Ethernet channels (Via VT6105M 10/100)
• I/O: DB9 serial port, dual USB port
• Board size: 6 x 6" (152.4 x 152.4 mm) - same as WRAP.1E
• Firmware: tinyBIOS


Links: PC Engines alix3d2 product file
PC Engines alix2d2 product file

I have been using these for almost 2 years now with excellent results. They run Voyage Linux which is Debian based. A simple script copies the everything compact flash and, once booted, runs the entire OS in RAM. It keeps Debian's apt package management system for super easy installation of MPD and ALSA. The boards offer 256MB or RAM, so you can, technically, buffer entire FLAC's to RAM ala cMP2.

My ALIX pulls FLAC files from my bedroom desktop via NFS. Thus, I have a dead silent listening room. I have MPD clients on my Nokia N800 which I use as a remote when I don't want to boo the laptop. The ALIX feeds a Wavelength Audio Brick V2 asynchronous USB DAC.

I also have the ALIX powered with a linear power supply as well. The voltage range is very wide for the ALIX; 7-18 volts. You can experiment with battery power as well.

The ALIX boards are very inexpensive. I paid $125 (single board quantities) USD for my 2d2. The case was approximately $12 USD. As these boards are general purpose single board x86 computers, they can also be recycled for future use, e.g., firewall, router, home automation/monitoring, automobile use, etc.

Here's a blog of a total newbie getting this setup going: Cheap silent USB Linux music server

There's also the ALIX 1d mini-itx that will runs Windows XP. Has a standard PCI slot as well.

Link: PC Engines alix1d product file

Hope this helps.

[nmiljac]

Well, the ARM based board I use drains 400mA peak at 5V (including the ethernet interface) which is max. 2W. No heatsinks on the board. The system-on-chip barely gets warm.

Much more important factor than power consumption is sound quality - a serial interface to DAC (e.g. I2S) rules here - it is the shortest and cleanest signal path from the system RAM to the DAC and is relatively insensitive to jitter. An x86 architecture features a longer signal path (buses that interface the DAC which is probably serial anyway). Other architectures offer much more simple interfacing.

[nyc_paramedic]

Originally Posted by nmiljac

Well, the ARM based board I use drains 400mA peak at 5V (including the ethernet interface) which is max. 2W. No heatsinks on the board. The system-on-chip barely gets warm.

Much more important factor than power consumption is sound quality - a serial interface to DAC (e.g. I2S) rules here - it is the shortest and cleanest signal path from the system RAM to the DAC and is relatively insensitive to jitter. An x86 architecture features a longer signal path (buses that interface the DAC which is probably serial anyway).

Ooops! I saw 30 watts in your last post and thought that was the power consumption of the board.

I recommended the ALIX --and the aforementioned blog-- because I think it's the easiest way for a total newbie to get up and running with an embedded system. I don't have any issues with ARM software or hardware, but it raises the bar for some. Although, if Voyage Linux was ported to ARM then that would be wonderful.

As far as sound quality, I'll leave that up to other people's own testing and tastes. I've never heard an ARM board playing music. I _would_ like to get together with other folks who have different embedded systems, though I'm in New York and you're in Germany. :/

Cheers.

[nmiljac]

Well I do have more than 30VA of transformers total in the box :-)

Cheers

[nyc_paramedic]

Originally Posted by nmiljac

Well I do have more than 30VA of transformers total in the box :-)

Cheers

I forgot to ask. Do you have more info on this board and how you are using it? Perhaps detailed in another thread? Which distribution are you using?

[nmiljac]

It's a Kwikbyte KB9202 (KwikByte - Home). But for my purpose any AT91 based board will do just fine.

I have built a customized OpenEmbedded based userland and a quite tightly configured kernel.

I agree that ARM can be a problem for newbies and surely is not something for the faint of heart. Especially when it comes to writing an ALSA driver for the DAC you've just built or erasing the boot loader :-) so I can agree that x86 is a good place to start.

How I use it ... it mounts the music from the server using AOE - apart from that it is relatively similar to your setup. I don't use an USB DAC but an I2S based one.

The server is silent and is placed in the listening room (x86).

Cheers