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Davespice
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Tested HDMI TO VGA Adapter for potential use in Schools

Tue Oct 15, 2013 8:52 am

Hey folks;
This might be of some help to schools which are looking into getting Raspberry Pi's in their computer rooms but don't want to have to buy new monitors. When you're setting up VGA monitors on the Pi the best thing to do first is look up the monitor specs online and find out the max / native resolution.

Image
In my case the native resolution was 1440x900. See here for mine. You need to Google something similar for your monitor. Usually if you just type the make and model number along with the word "specifications" you'll find what you need.

Once you know the max / native resolution you need to look it up, under group 2 (DMT), in this list, that will then tell you what HDMI mode number you have to use in config.txt.

Then you need to get a good HDMI to VGA adapter.
This is one of the cheapest ones I have found; http://www.amazon.co.uk/dp/B0088K7QUQ
Image
At under £10 that makes it pretty viable to equip a computer room with them and saves the expense of buying new digital monitors.

In my tests that adapter worked pretty well. Although the monitor I was using it with caused some blanking. So I used hdmi group 2 and mode 46 for reduced blanking in the end. I then fiddled with over scan settings to move it around a little bit more to perfect it. There was still a bit of a blank area on the left, but I think that is about as good as you'll get in some cases.

Blanking is when the left hand edge of the picture starts somewhere in the middle with most of the image disappearing off the right hand edge of the screen. If you ever see this try one of the reduced blanking modes.

It's always a good idea to just test that the hdmi to vga adapter is working by setting hdmi_safe=1 in config.txt, then once you've verified that is working move onto trying to get the max / native resolution working. That said, the config.txt settings I used were;

Code: Select all

hdmi_force_hotplug=1
hdmi_ignore_edid=0xa5000080
config_hdmi_boost=4
hdmi_group=2
hdmi_mode=46
hdmi_mode=46 in group 2 is 1440x900 with reduced blanking.

Obviously your monitor is probably different to my one so you'll want to use a different hdmi mode number. You may need to play around trying to get the best mode with a refresh rate that your monitor likes. The best thing to do is to SSH into the Pi using Putty to make the changes to config.txt, then reboot and watch how the screen looks.

Also, my monitor has built in speakers which can be connected to the Pi using a 3.5mm headphone jack cable. You can use the following command to make the Pi redirect audio output to the audio jack. Then you should be able to get sound out.

Code: Select all

sudo amixer cset numid=3 1

pwinwood
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Re: Recommended HDMI TO VGA Adapter for Schools

Wed Oct 30, 2013 6:59 pm

Before following this recommendation please review this http://www.raspberrypi.org/phpBB3/viewt ... =28&t=9819 discussion. Sorry Dave, it is not really suitable due to it's power consumption from the 5volt line on the HDMI port. Unless this model has significantly reduced consumption?

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mahjongg
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Re: Recommended HDMI TO VGA Adapter for Schools

Wed Oct 30, 2013 10:50 pm

this one http://www.ebay.com/itm/New-HDMI-A-Male ... 1c35799eb6 looks more promising, when used with external power supply, (provided by a powered hub perhaps) but I have no independent conformation it works well.

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Davespice
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Re: Recommended HDMI TO VGA Adapter for Schools

Thu Nov 28, 2013 11:22 am

pwinwood wrote:Before following this recommendation please review this http://www.raspberrypi.org/phpBB3/viewt ... =28&t=9819 discussion. Sorry Dave, it is not really suitable due to it's power consumption from the 5volt line on the HDMI port. Unless this model has significantly reduced consumption?
I used it for a many hours without any issues, the Pi was no warmer than usual.
I ran it for a good 8 hours showing the hello_teapot demo at 1440x900.

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Re: Recommended HDMI TO VGA Adapter for Schools

Sat Dec 07, 2013 10:51 pm

FWIW, I've just purchased and performed preliminary testing of one of these: http://www.amazon.co.uk/gp/product/B00C ... UTF8&psc=1
Appears to be manufactured by/for the same company as @DaveSpice's original suggested device, but is a bit cheaper and is supplied with a USB power lead and right-angle HDMI adapter. The product "blurb" implies that it may be used with a Pi w/o external power but, since a lead is provided and I have a suitable dual-output PSU (usually used to power a USB hub when I need to with my model A Pi) I chose to "play safe" and provide such. First impressions have been good, the only "down-side" is that, since it plugs directly into the Pi it cannot be used with some Pi case types. I have only tried the video output (with three monitors and two different, B2 Pi's) so far and have yet to try the audio output. Pictures and monitor photo's etc. can be seen here: http://www.cpmspectrepi.webspace.virgin ... erter.html
Trev.
Last edited by FTrevorGowen on Sun Dec 08, 2013 9:36 am, edited 1 time in total.
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my 2xP3A+, P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

toxibunny
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Re: Recommended HDMI TO VGA Adapter for Schools

Sat Dec 07, 2013 11:57 pm

Davespice wrote:
pwinwood wrote:Before following this recommendation please review this http://www.raspberrypi.org/phpBB3/viewt ... =28&t=9819 discussion. Sorry Dave, it is not really suitable due to it's power consumption from the 5volt line on the HDMI port. Unless this model has significantly reduced consumption?
I used it for a many hours without any issues, the Pi was no warmer than usual.
I ran it for a good 8 hours showing the hello_teapot demo at 1440x900.
I can't think of a nicer way to say this, so: "I hope you're not making a general recommendation based on your own personal experience. You represent a sample size of 1, at apparently only 1 tested resolution. You should tone down your 'recommendations' and simply report your experience."

Just keeping it safe, dude. There have been reports of burnouts, there is a datasheet listing a max. current draw for a specific HDMI-related diode. It seems to be the general consensus that most unpowered HDMI>VGA converters require more than that diode is rated to handle. It's good that your raspi+converter combo has been able to handle what you've thrown at it so far, but I think you're overstepping the mark making it a general recommendation, that's all...
note: I may or may not know what I'm talking about...

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Davespice
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Re: Tested HDMI TO VGA Adapter for potential use in Schools

Sun Dec 08, 2013 12:48 pm

toxibunny wrote:I can't think of a nicer way to say this, so: "I hope you're not making a general recommendation based on your own personal experience. You represent a sample size of 1, at apparently only 1 tested resolution. You should tone down your 'recommendations' and simply report your experience."
Okay well, I take your point however the only place where I actually infer that something is generally recommended is in the subject of this topic.
I will change it.

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Re: Tested HDMI TO VGA Adapter for potential use in Schools

Sun Dec 08, 2013 2:57 pm

@Trevor - that looks like an excellent find :)

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psutton
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Re: Tested HDMI TO VGA Adapter for potential use in Schools

Sun Dec 22, 2013 9:00 pm

If your monitors have dvi input you can get hdmi to dvi converters far cheaper. I put an article on my blog about the different types of connector.

http://zleap.net/raspberry-pi-video/

hope this helps and perhaps saves some money

Paul

Phill Rymer
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Re: Recommended HDMI TO VGA Adapter for Schools

Tue Dec 24, 2013 1:08 am

mahjongg wrote:this one http://www.ebay.com/itm/New-HDMI-A-Male ... 1c35799eb6 looks more promising, when used with external power supply, (provided by a powered hub perhaps) but I have no independent conformation it works well.
I use this one worked straight out the box no code to alter :D

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mahjongg
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Re: Recommended HDMI TO VGA Adapter for Schools

Tue Dec 24, 2013 1:54 am

Phill Rymer wrote:
mahjongg wrote:this one http://www.ebay.com/itm/New-HDMI-A-Male ... 1c35799eb6 looks more promising, when used with external power supply, (provided by a powered hub perhaps) but I have no independent conformation it works well.
I use this one worked straight out the box no code to alter :D
how did you power it? an external PSU? or via a powered hub perhaps, or no external power?

Phill Rymer
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Re: Tested HDMI TO VGA Adapter for potential use in Schools

Tue Dec 24, 2013 5:35 am

from power cable that came with it connect to psu with 2 usb sockets

gruff22
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Re: Tested HDMI TO VGA Adapter for potential use in Schools

Mon Jan 06, 2014 9:51 am

http://www.ebay.co.uk/itm/181232111376

I have used one of these with two different SVGA LCD monitors without problem, please read the above advice though. :o

VicFRF
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Re: Tested HDMI TO VGA Adapter for potential use in Schools

Thu Jul 14, 2016 2:02 am

How do I add that code to RetroPi? (Pi-Noob here...)

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