rwgast
Posts: 31
Joined: Sat Feb 18, 2012 10:26 pm
Contact: Website

Re: genral hardware concerns?

Sat Feb 18, 2012 11:53 pm

first off let me start off by saying im really excited about the pi ever since it was recommended to me. ive been hacking old armv6 qualcom boards out of phone to run an arm based development enviroment for assembly language and android. basically just running debian squeeze and ssh or vnc"ing into them. im moving away from x86 slowley as i see it arm is the future and android and win ce are huge platforms for developers.

Anyways ive got alot of hardware already lined up for the pi and im hoping its all gonna work the way i hope.

first off i plan on using a widescreen 15 inch vga only lcd. i bought a composite to vga adapter since it seems like the cheapest option. ive used composite out on plenty of pcs so it makes me a little curious since ive had problems in the past. my main concern is will the composite still drive the monitor at 1366x768? and if so will it be to fuzzy to read in x-win?

also i have some power concerns, first off i have a universal power supply from wal mart that goes from 3 to 12 volts with difrent adapters it also has a usb power port im assuming any usb psu should work on the micro usb port? im also trying to keep wires to a minimal and would rather use a passive usb hub. if all im trying to power is a mini bluetooth adapter a mouse maybe and either an external cd or floppy drive and usb key would i be fine?

lastly im sord of worried about getting android 4 ported to this thing due to ram size. if im swapping to a class 10 sd should that give me a decent boost.

thanks guys keep up the awesome work!

Lynbarn
Posts: 464
Joined: Wed Jan 04, 2012 11:03 pm
Contact: Website

Re: genral hardware concerns?

Sun Feb 19, 2012 12:11 am

First of all, welcome to the forum, rwgast.

As for using composite video, THIS THREAD may give you further information

If you intend powering an external HDD through USB, then a powered hub may be a better option - I think you may start encountering some difficulties.

Porting Android 4 sounds like something of a challenge - be interested tohear how thatgoes. Regarding the use of class 10 SD cards, you may want to read THIS THREAD before commiting to any purchase.

drgeoff
Posts: 10324
Joined: Wed Jan 25, 2012 6:39 pm

Re: genral hardware concerns?

Sun Feb 19, 2012 1:30 am

rwgast said:

.... im also trying to keep wires to a minimal and would rather use a passive usb hub. if all im trying to power is a mini bluetooth adapter a mouse maybe and either an external cd or floppy drive and usb key would i be fine?

The Bluetooth adapter, mouse and USB key will probably be fine on a passive USB hub.  But the USB ports on the RP do not supply enough power for a  CD or floppy drive.

rwgast
Posts: 31
Joined: Sat Feb 18, 2012 10:26 pm
Contact: Website

Re: genral hardware concerns?

Sun Feb 19, 2012 2:21 am

Ok thanks for the answers. The only thing im still unclear about is the screen. I actually had read the thread about the composite jack posted above but it just confused me more. I have had plenty of video cards with composite T.V. out on them and they were able to output 1366x768 so im assuming it shouldn't be a problem and thread listed above is basically stating what resalutions you will get if you plug into a tv.

Tomo2k
Posts: 127
Joined: Mon Dec 19, 2011 10:00 pm

Re: genral hardware concerns?

Sun Feb 19, 2012 9:25 pm

rwgast said:


I have had plenty of video cards with composite T.V. out on them and they were able to output 1366x768


They may have had framebuffers that size, but your TV didn't show it – unless you actually meant Component (three coax cables, often red, green and blue)

Composite video tops out at 625 lines of data for PAL, except that they aren't all for the image – in the UK we actually used the top few for Teletext/Ceefax!

PAL allows up to 576 lines for the image, although most domestic TVs don't actually show all of them either.

Horizontal resolution is a bit more complicated as it's two analog signals, a "colour burst" at the start of the line, then brightness along the line – so there is a higher "brightness" resolution than "colour".

You can generally assume about 720 pixels per line – that's what PAL DVDs and Freesat/Freeview SD digital transmissions use.

So a reference PAL monitor has a native resolution of 720 x 576.
- Though not all analog TVs can actually show the whole thing anyway (overscan).

NTSC is worse – which may be why HD took off so much faster in the US compared to Europe.

Andre_P
Posts: 241
Joined: Sun Aug 28, 2011 7:57 am

Re: genral hardware concerns?

Sun Feb 19, 2012 10:02 pm

The Colour Burst is (was !) used for synchronisation at the start of each line, the rest of the line the phase of the signal was then used to determine the colour, while the magnitude conveyed the luminance of the line.

The Colour Burst changed phase on each line, thus the term Phase Alternate Line (PAL).

The reason for the phase change was to average out noise.

NTSC has (had !) a similar approach but the the phase of the initial colour (or dare I say it color !) burst stayed the same throughout the picture, thus any noise corrupted the colour significantly, this is why NTSC is sometimes taken to mean

Never The Same Colour/Color.

SECAM was interesting as it was partially a digital signal though I don't know any more than that.

drgeoff
Posts: 10324
Joined: Wed Jan 25, 2012 6:39 pm

Re: genral hardware concerns?

Sun Feb 19, 2012 10:21 pm

Andre_P said:


…, the rest of the line the phase of the signal was then used to determine the colour, while the magnitude conveyed the luminance of the line.



Not quite.  The colour is conveyed as two colour difference signals which jointly modulate the amplitude and phase of a high frequency subcarrier. The subcarrier is added to the luminance signal.  For more details see eg http://en.wikipedia.org/wiki/NTSC and http://en.wikipedia.org/wiki/PAL.

rwgast
Posts: 31
Joined: Sat Feb 18, 2012 10:26 pm
Contact: Website

Re: genral hardware concerns?

Mon Feb 20, 2012 12:36 am

Maybe im mistaken but i really thought i used composite out with both a pc and xbox and both scaled to the screen resalution.

So is there a way to get a universal hdmi/dvid driver board for lcds? When reading up on this before i was fairly confused. Id love to acually drive this lcd on battery power without the casing. But just having it work as a decent display is good enough.

foo
Posts: 52
Joined: Thu Dec 29, 2011 12:49 am

Re: genral hardware concerns?

Mon Feb 20, 2012 6:39 am

VGA monitors are really a non-starter with the RPi.

If you want a native 1366x768 resolution, you'd need to get a converter from HDMI to VGA (HDMI is basically the same as DVI but with a different connector, so a *digital* DVI->VGA converter box would work as well).

Getting a new, basic LCD monitor that takes HDMI/DVI would be similar in price or even cheaper than finding such a converter, plus would most likely go to 1920x1080.  Or hunt Craigslist/classifieds for a decent used monitor.  There are plenty to be had.

User avatar
RaTTuS
Posts: 10539
Joined: Tue Nov 29, 2011 11:12 am
Location: North West UK
Contact: Twitter YouTube

Re: genral hardware concerns?

Mon Feb 20, 2012 9:55 am

Re the power,

you may be better off getting a powered USB hub and powering the RPi from that as well as the other stuff
How To ask Questions :- http://www.catb.org/esr/faqs/smart-questions.html
WARNING - some parts of this post may be erroneous YMMV

1QC43qbL5FySu2Pi51vGqKqxy3UiJgukSX
Covfefe

Return to “General discussion”