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View Full Version : . Multiple VGA Displays - "Heads-Up-Display" Project Discussion.



marzec309
01-24-2009, 03:08 AM
Is it possible to drive multiple VGA displays with propeller? If so would it be possible to run three displays? I've been interested id making a digital dash display for my car. that will display all the usual things you find on your dash but in a more fancy way and due to the dash configuration I wouldn't be able to fit one large display, but would be able to arange two or three 7" displays in the space i have available. i know the propeller has the power to hands the graphics as these would just be simple gauges, and information display the could show diagnosis info from the ECU.
has anyone ever tried to run more then one display off the propeller?

Post Edited (marzec309) : 1/27/2009 9:08:09 PM GMT

Computer Geek 101
01-24-2009, 03:10 AM
I did a job display board with 2 vga monitors

http://forums.parallax.com/forums/default.aspx?f=21&m=264369

Mike Green
01-24-2009, 03:50 AM
Each VGA display requires a group of 8 I/O pins (0-7, 8-15, 16-23), a cog, and some memory for the display buffer. Full screen graphics just barely fits in memory, so you're limited to a text display although you could have small "patches" of graphics using the tiled VGA drivers. Again, the main limitation is memory and that depends on the resolution you're using and the percentage of graphics.

marzec309
01-24-2009, 04:25 AM
Well the resolution of the 7' displays, that I'm looking at is pretty low. I think something like 800x480. I have tossed around the idea of using a single propeller per display or at least one for all the displays. Then having a master that would be interfaced to a USB drive. The USB drive could be a few GB's, which should be enough to hold all the graphics. With this setup i should still have plenty of I/O's left for interfacing to various sensors.

Cole Logan
01-24-2009, 05:52 AM
I have thought about the samething but Haven't had a chance to try anything out. I would think the biggeist limitation would be memory.

marzec309
01-26-2009, 07:22 AM
Well as i was driving home today. I took a little time to study the dash (At red lights of course). Looks like Two 7" Displays would be all I can fit, without too many modifications. Here is what I'm thinking will work. Though its possible that not all of the ideas will make it to the final design.

Post Edited (marzec309) : 1/25/2009 11:27:23 PM GMT

awesomeduck
01-27-2009, 01:28 AM
I have been looking at a very similar project, but in fact have been leaning towards the NTSC/PAL interfaces since you can get rear view mirrors with 2 LCDs built in. Supposedly the mirror looks normal when the LCDs are turned off. NTSC uses 1/2 the pins of VGA too.

I have been looking at a similar concept...wondering if you are using the ELM chips for OBDII, would be interested in sharing info and code on this project. My knowledge of the Prop is based mostly on what I have read in the Hydra book. I am with Mike Green on this though....the memory is going to be tight for two displays up at once.

marzec309
01-27-2009, 04:27 AM
Ya, from what I gather memory will be an issue, But I hope I can get around this by using the SD card (Wont know for sure until i can test). As of right now, I don't have any parts. Its just in a research stage. I have also seen review mirrors with monitors in them, but they don't really look all that great when turned off.(how about just using a small monitor for the rear view mirror?)

As for the OBDII, I'm planning to use a Microchip MCP2551 CAN Transceiver. I found a site that covers the CAN protocal here:

en.wikipedia.org/wiki/On_Board_Diagnostics#OBD-II_Diagnostic_connector (http://en.wikipedia.org/wiki/On_Board_Diagnostics#OBD-II_Diagnostic_connector)

and here:

en.wikipedia.org/wiki/OBD-II_PIDs#Bitwise_encoded_PIDs (http://en.wikipedia.org/wiki/OBD-II_PIDs#Bitwise_encoded_PIDs)

So the software side of the OBD interface looks pretty easy and should be able to pull most of the sensor data right from the ECM. Now, I've used a lot of the Basic stamps in my projects, but the Prop is going to be new to me. From what i hear the learning curve is not that bad. As far as sharing code, I would love to when I get to that point. Two minds are definitely better then one.

Cole Logan
01-27-2009, 08:42 AM
I've been looking for something like that can bus chip. I have a megasquirt I was wanting to get the data from it.

Paul Baker
01-27-2009, 09:01 AM
It appears that you intend on being able to pipe AV (DVD) to the displays, just so you know, in almost all jurisdictions it is illegal to have movies or television diplayed anywhere the driver would be able to view it, this includes a display mounted on the passenger side. You could use it for this purpose while the ignition is off, but not when the ignition is on.

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Paul Baker (mailto:pbaker@parallax.com)

Invent-O-Doc
01-27-2009, 10:45 AM
Use 2 or 3 propellers and link them. They are cheap enough.

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Thomas Talbot, MD
Gunpowder, MD, USA

awesomeduck
01-27-2009, 11:07 AM
Interesting. I had not seen the Microchip. I was looking at the ELM323. Since this thread is about VGA, I am going to create a new topic on OBDII. I looked in the object exchange and have not seen any mention of drivers for these chips...maybe we are in uncharted waters.

marzec309
01-28-2009, 04:55 AM
awesomeduck said...
Interesting. I had not seen the Microchip. I was looking at the ELM323. Since this thread is about VGA, I am going to create a new topic on OBDII. I looked in the object exchange and have not seen any mention of drivers for these chips...maybe we are in uncharted waters.


You shouldn't need drivers for the MCP2551. as this chip is a serial to CAN Bus Interface. Any serial connection will do the trick.


Invent-O-Doc said...
Use 2 or 3 propellers and link them. They are cheap enough.


Yes, that has been a thought. One each as display drivers, then a master unit...


Paul Baker said...
It appears that you intend on being able to pipe AV (DVD) to the displays, just so you know, in almost all jurisdictions it is illegal to have movies or television displayed anywhere the driver would be able to view it, this includes a display mounted on the passenger side. You could use it for this purpose while the ignition is off, but not when the ignition is on.


Yes, I am aware of those laws, But the AV connection to the Heads-Up-Displays(Hay I just came up with a good name for my project.), was implemented so I can feed the signal from the GPS. This would be allowed by law(I think?). And will probably have Code to do what you suggested, So the only signal that will be allowed on the Heads-Up-Display, while in gear will be the GPS.


And yes I have gotten a little of subject with my original post. Thus i have edited the Subject for this post. I'm still interested in info for Dual VGA's.

Post Edited (marzec309) : 1/27/2009 11:49:56 PM GMT

awesomeduck
01-29-2009, 09:22 PM
While not VGA, there seems to be a new class of USB mini displays hitting the market, for example:
http://www.slashgear.com/century-japan-lcd-4300u-43-inch-usb-monitor-1018916/

Might it be possible to use the USB interface on the Prop Demo and Hydra to drive something like this?

marzec309
01-30-2009, 03:41 AM
Those USB ports on the Prop Demo and Hydra are strictly slaves. Though it may be possible to to hack the displays.

virtuPIC
01-30-2009, 03:58 AM
marzec309 said...
Those USB ports on the Prop Demo and Hydra are strictly slaves. Though it may be possible to to hack the displays.


Right. But that's not really bad news. The Propeller develops thrust enough to emulate a USB host. Even an AVR ist strong enough...

Oops! I posed the next challenge. http://forums.parallax.com/images/smilies/rolleyes.gif Well, I will be interested in the result and in the development... http://forums.parallax.com/images/smilies/smile.gif
--
Airspace V - international hangar flying!
http://www.airspace-v.com/ggadgets for tools & toys

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Airspace V - international hangar flying!
www.airspace-v.com/ggadgets (http://www.airspace-v.com/ggadgets) for tools & toys