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Forum Index : Microcontroller and PC projects : Composite Out on Maximite driving a chine
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| mookster1 Regular Member  Joined: 10/06/2011 Location: New ZealandPosts: 81 |
Hi all, I recently realised that my no-name-brand GPS unit has a 2.5mm AV input on the side. So I figured out which pin did which on the plug and managed to get a Playstation 2 displaying video on the screen. So I thought about configuring my Maximite (from the Altronics kit) for composite video and plugged it into the GPS. And nothing happened. When there's a video input the GPS automatically switches over to the AV input. I plugged the Maximite into my TV (via composite) and it worked beautifully. So the GPS doesn't like the output from the Maximite. Does anyone have any experience with this? My theory at this stage is that the GPS only accepts a colour video input and as the Maximite only outputs in monochrome (measuring the signal on my multimeter only reveals 0.5VAC whereas the PS2 was about 2.0VAC). I do not know much about the standard so any help would be appreciated  Capacitance is futile - roll on 2012! |
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| mookster1 Regular Member Joined: 10/06/2011 Location: New ZealandPosts: 81 |
Okay, I thought of a possible solution but I'm not entirely sure how to implement it. Basically it involves rewriting the part of the firmware that deals with composite video to "fake" a chroma signal, so the GPS/any other screen that wants colour video doesn't ignore the video. Would the PIC32 be capable of doing this as well? I realise it's not capable of doing colour video because of lack of memory, but is it capable of "faking" a chroma signal so that anything that requires this signal can display the video? Failing this, does anyone know of any other solutions to get colour composite video, if not "pretend colour" as above? Cheers Capacitance is futile - roll on 2012! |
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djuqa Guru  Joined: 23/11/2011 Location: AustraliaPosts: 447 |
Could work, but why spend time,money on PIC32 MM/DM which does what it DOES in an excellent fashion. Don't be critical of what it can't do, be amazed at what it does. If colour is that much of a need investigate one of the many other solutions that offer colour output. VK4MU MicroController Units |
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| mookster1 Regular Member Joined: 10/06/2011 Location: New ZealandPosts: 81 |
Hi djuqa It's not that I desperately need colour (of course it would be nice , but I don't have a real need for it), it's that my composite-input screen is rejecting the video, probably on the basis that the signal doesn't have any colour component (I can see why; my television works fine as a composite video screen for the Maximite without the colour signal, so it would be pointless in most cases for the Maximite to do this, and the GPS normally deals with colour reversing cameras, so anything in black and white would normally be a malfunctioning camera.) So I was wondering if there was an easy way of getting around this by changing the video subroutine so that it generates a chroma signal too, but that chroma signal is always white, so anything connected to the MM thinks it's a colour signal and displays it, but it's actually (as before) black and white.
Cheers Capacitance is futile - roll on 2012! |
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| djuqa Guru Joined: 23/11/2011 Location: AustraliaPosts: 447 |
I have used the DM and MM on several composite input devices (3.5in Rear camera monitor to 55inch PLASMA) and found ALL work ok with B/W signal from MM/DM devices. Any device that is having problem with the signal maybe one at fault. Not having CHROMA signal should NOT affect the display. Have you tried changing PAL/NTSC setting? VK4MU MicroController Units |
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| mookster1 Regular Member Joined: 10/06/2011 Location: New ZealandPosts: 81 |
OK then, that is a good point and I'll look into that
The screen I'm using accepts a PAL input and I've tested it with several devices to prove this, the only one refusing to work being the Maximite. So I'll play around with the video output setting on that and see where that gets me. Thanks for your advice! Capacitance is futile - roll on 2012! |
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| mookster1 Regular Member Joined: 10/06/2011 Location: New ZealandPosts: 81 |
Okay, I've just tried switching between video modes on the Maximite... and neither of them yielded any results  . I made doubly sure the jumper was on, because I'm no stranger to stupid mistakes . I can't change video modes on the GPS end so I couldn't try that (as it was the manual didn't even describe this feature, and what little was described was done so in incredibly amusingly bad Engarin.)Capacitance is futile - roll on 2012! |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3801 |
The video out is done by DMA from RAM as I recall (*) so how would you change that for anything else (CHROMA/etc)? Beats me. I think add hardware... (*) read the code :) John |
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| mookster1 Regular Member Joined: 10/06/2011 Location: New ZealandPosts: 81 |
Hey JohnS, Yes that is a fair point. The video is done by reading the video memory and using DMA to get it out and I did forget about this fact. Unfortunately I barely know C and it would be an incredibly steep learning curve to try to pull this off. I've been thinking about designing an external video controller for this purpose so not only will it have a composite output, it could possibly do colour... While it's slightly overkill (and maybe a "pi in the sky" judging from the posts I've seen on this forum), the Raspberry Pi would happily do the job. Capacitance is futile - roll on 2012! |
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donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Have a look at this thread for MOD-VGA: http://www.thebackshed.com/forum/forum_posts.asp?TID=4568&KW =mod-vga However I believe the current hold up is software, not hardware. It is being worked on. Cheers Don... https://www.dontronics.com |
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| Vikingboy Regular Member Joined: 23/09/2011 Location: AustraliaPosts: 82 |
Hi, As djuqa said I too doubt that it is the lack of a colour burst on the Maximite signal that is stopping it being displayed, a couple of questions, does the GPS unit switch over to the video input when you connect the Maximite and then display nothing ? or does it not switch over at all ?, also is it possible to manually switch to the video input ? , if so, what do you see when you do. Another thing to look at is the video levels, if it is the case that you see a blank screen it is possible that the GPS unit has contrast and brightness settings way out of range for the Maximite. A way to do a further test is to route your Maximite through another device, like a video recorder input and then out of that into the GPS unit to see if that shows anything. I am sure there is probably a simple way to solve your problem without re-writing the mm-basic code and hardware for colour just to display on your device :) rgds, An drew |
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| mookster1 Regular Member Joined: 10/06/2011 Location: New ZealandPosts: 81 |
Hi Vikingboy, Normally when the GPS encounters a video signal, it just switches over to the video signal. Unfortunately there are no settings to tweak, just plug, play and hope something happens
When I plugged my Maximite in and switched it on, the GPS didn't even bother to switch over. However, one thing I have not tried is routing the signal through something else, and that idea actually sounds crazy enough that it might just work 
I'll give it a crack and see what happens. Thanks!  Capacitance is futile - roll on 2012! |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3801 |
I'll also say Thanks as in theory I know to try such things but it's great to be reminded! John |
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| mookster1 Regular Member Joined: 10/06/2011 Location: New ZealandPosts: 81 |
I know it's a couple months later but I've tried plugging the GPS into a VCR with the Maximite on the video input, and I got a brief glimpse of the Maximite on the GPS before it switched back over to the menu. I can then switch (on the VCR) back to a video tape and it works fine, only dropping the signal when it gets the signal from the Maximite. The TV does this too, so I think (dunno what the design engineers of the GPS were thinking...?) that it rejects the signal on the basis that it is not colour. I've ordered a Raspberry Pi and intend to use it as a serial driven video interface (colour as well! ) between the Maximite and the screen. For the record I can even give the MM an HDMI output using this method as the Pi has HDMI Out as well as composite.Capacitance is futile - roll on 2012! |
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| Vikingboy Regular Member Joined: 23/09/2011 Location: AustraliaPosts: 82 |
Hi again, One thing to try is that some VCRs need to be in what is called "E to E" mode for the input to show up on the VCRs outputs, usually it is accomplished by pressing the record button only, ie not with the play button, then whatever is on the input should pass straight through to the output. If your VCR dosn't support this mode you may need to put a tape in ,or even try actually recording the input to a tape and see if this passes the signal. hope you get this sorted eventually ;) Andrew |
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