sge
Posts: 16
Joined: Sun Oct 23, 2011 3:12 am

Re: Devices that you will be purchasing for use with you Rpi

Sat Nov 05, 2011 4:57 am

Breakdown of purchases I consider necessary for my usage plans: (in Australian Dollars)

* (\"EDUP 150Mbps 802.11n\") Wifi dongle ($7.35)
* (Generic brand) Bluetooth V2 dongle ($1.27)
* 7-port powered USB hub (gives 500mA, enough to power the dongles) $5.44
* USB AC Adapter with Micro USB Cable, $3.99 (An expensive one which claims to supply 1000mA max. I trust it enough to power RPi. It comes with the cable too. I also bought a cheaper one below.)
* Raspberry Pi Model B $35 + $10 (assumed shipping cost)
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Total cost: $18.05 (Accessories) + $45 (RP itself) = about $63

(I made sure the wifi and bluetooth dongles had Linux (and ARM) support and were those nice \"nano\" dongles that are barely bigger than a USB port itself.)

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Breakdown of purchases that will be used with RPi, but I either have have uses for without a RPi or are nice non-necessities for the device: (again, in AUD)

* 3 foot HDMI cable for $2.02 (There is no difference between a $5-$10 cable and a $50 cable, but I\'ve heard there can be differences between a $1 cable and a $5.)
* Externally powered 1-terabyte 3.5\" external hard drive (for $60)
* Another USB AC Adapter for $1.26 (if it doesn\'t output enough power for Raspberry Pi, I don\'t mind, I\'ll find another use and use the more expensive, trustworthy one above)
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Total Cost: $3.28 + $60 (harddrive)

The above accessories are not necessary. I could make do without a dedicated Raspberry Pi HDMI cable and didn\'t need TWO USB AC adapters etc

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In cases where there were near identical items at similar prices from different eBay vendors I bought from the higher feedback vendor. Any small extra costs gave around 1% extra positive feedback, which I\'m happy to pay as a form of psychological insurance.

kme
Posts: 448
Joined: Sun Sep 04, 2011 9:37 am

Re: Devices that you will be purchasing for use with you Rpi

Sat Nov 05, 2011 5:25 am

Ehmm sge... R-PI isn\'t a PC as you know it. You want to put this on the single USB bus:
WiFi, Bluetooth, external hub, LAN and a HDD. Besides keyboard and mouse, I suppose.

You better realize you have only 480 kb/s (kilo bit/sec - not kilo byte/sec) totally for all of these. In half duplex, that is.

sge
Posts: 16
Joined: Sun Oct 23, 2011 3:12 am

Re: Devices that you will be purchasing for use with you Rpi

Sat Nov 05, 2011 6:40 am

[quote]Quote from kme on November 5, 2011, 05:25
Ehmm sge... R-PI isn\'t a PC as you know it. You want to put this on the single USB bus:
WiFi, Bluetooth, external hub, LAN and a HDD. Besides keyboard and mouse, I suppose.

You better realize you have only 480 kb/s (kilo bit/sec - not kilo byte/sec) totally for all of these. In half duplex, that is.[/quote]

I knew the R-Pi was reasonably weak but I didn\'t realize the USB bandwidth was THAT low. 480kbits/s = 60 kiloBYTES/second right? That wouldn\'t even be close to being able to play 1080p video from a USB hard drive, would it? Does each USB port on the model B give 480kbit/s independently?

The most I was planning to would chuck at the wifi would be streaming YouTube videos (and I was planning to use Bluetooth to build my my own user interface using a single Wii Remote.) I think 60kB/s should be fine for that, and USB keyboards wouldn\'t take much at all I think. I\'m not planning on filling all the ports on the USB hub with devices, it\'s mainly there to supply power to the devices instead of drawing it from the R-Pi.

I can change my plans to accommodate using wired (ethernet) networking and have the hard drive attached to another device on the network (so it pulls data over ethernet.) Raspberry Pi has 10/100 ethernet right? So if my switch/router/other devices are compatible and conditions are favorable it should run at (or near) its maximum bandwidth of 100mbps (which is equal to 12.5megaBYTES/second). This should be high enough for my aim to stream 1080p video (but maybe not at super high bitrates) from the net or a hard drive.

EDIT: Wait a second, R-Pi has USB2.0 right? That\'s 480MEGAbits/second (which is 60 megabytes/second). That\'s heaps (well compared to 60 KILObytes/second it is), enough to access 1080p video at high bit rates (higher than R-Pi can decode, bandwidth is then no longer the bottleneck I think). Wifi, bluetooth, usb keyboard and mouse may not be able to work at maximum speeds, but it\'s possible to have all this working concurrently I think. But like I said, I\'m flexible enough to screw wifi and stick with ethernet if this is not the case.

EDIT2: 100mbps is 12.5mB/s. I wrote 20 for some reason.

No1
Posts: 5
Joined: Fri Aug 26, 2011 6:07 pm

Re: Devices that you will be purchasing for use with you Rpi

Sat Nov 05, 2011 12:44 pm

[quote]Quote from sge on November 5, 2011, 06:40
I knew the R-Pi was reasonably weak but I didn\'t realize the USB bandwidth was THAT low. 480kbits/s = 60 kiloBYTES/second right? That wouldn\'t even be close to being able to play 1080p video from a USB hard drive, would it? Does each USB port on the model B give 480kbit/s independently?

[...]

I can change my plans to accommodate using wired (ethernet) networking and have the hard drive attached to another device on the network (so it pulls data over ethernet.) Raspberry Pi has 10/100 ethernet right? So if my switch/router/other devices are compatible and conditions are favorable it should run at (or near) its maximum bandwidth of 100mbps (which is equal to 20megaBYTES/second). This should be high enough for my aim to stream 1080p video (but maybe not at super high bitrates) from the net or a hard drive.[/quote]

Yes, the R-Pi has a USB 2.0 port with a max bandwidth of 480 megabit/sec or 60 megabyte/sec (excluding overhead), but the chip itself only has one port (the Model B basically uses an chip that acts as a 3 port hub, with one port converted to an ethernet port), so the total data bandwidth is limited to that single port, no matter that the Model B has two usb ports and an ethernet, they still share the same limit, so it shouldn\'t matter much if you get the data from a usb HDD, stick, via ethernet or wifi, except that you might need to power an additional device/server. (10/100 ethernet is 100 megabit/sec or around 12.5 megabyte/sec - but for large transfers on a desktop computer typical transfer rates are around 8-10 megabyte/sec - HDD transfer over usb 2 peak at around 25-30 megabytes/sec).

sge
Posts: 16
Joined: Sun Oct 23, 2011 3:12 am

Re: Devices that you will be purchasing for use with you Rpi

Sat Nov 05, 2011 2:06 pm

That makes sense: a maximum of 480mbps to share somehow between USB devices and ethernet.

So does that mean a R-Pi model A is with a USB hub + a USB to ethernet adapter is effectively same as a model B (except for RAM)?

I\'m still a little skeptical that it is. I hope we are all wrong and it turns out that the \"LAN9512\" chip allows 480mbps USB AND 10/100 ethernet operating at full speeds at the same time. Or even both USB2.0 ports running at 480mbps each and 10/100 ethernet at full :D

kme
Posts: 448
Joined: Sun Sep 04, 2011 9:37 am

Re: Devices that you will be purchasing for use with you Rpi

Sat Nov 05, 2011 2:15 pm

Damn, of course 480 Mb/s. Must have been sleeping...

Yes the A model with a USB hub with LAN port is effectively a B model. And all ports share the 480 Mb/s (I got it right!) AND it\'s half duplex.

bnolsen
Posts: 76
Joined: Sat Aug 13, 2011 5:37 pm

Re: Devices that you will be purchasing for use with you Rpi

Sat Nov 05, 2011 2:37 pm

That lan port doesn\'t help with the IO bottlenecks. You get 1 usb port worth of throughput regardless.

kme
Posts: 448
Joined: Sun Sep 04, 2011 9:37 am

Re: Devices that you will be purchasing for use with you Rpi

Sat Nov 05, 2011 2:47 pm

[quote]Quote from bnolsen on November 5, 2011, 14:37
That lan port doesn\'t help with the IO bottlenecks. You get 1 usb port worth of throughput regardless.[/quote]Correct, but you need a \"USB hub with LAN port\" to make an A model similar to a B model (except for the RAM). But there is only 480 Mb/s to play with all together.

subminiature
Posts: 43
Joined: Wed Nov 02, 2011 6:27 pm
Contact: Website

Re: Devices that you will be purchasing for use with you Rpi

Mon Nov 07, 2011 11:24 pm

In expecting to need a powered USB hub is there one that might be built in a case and have a way of having one neat power connector to both the Raspberry Pi and the hub?

I am thinking of something like the 3.5\" ones for PCs that fit where a floppy drive might be. The ones I have seen are not suitable having eSATA, Firewire and several memory card slots but only 2 USB sockets.

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