Video interface help

[Rooster]

I am in the brainstorming phase of my next project and am looking for some suggestions.

I want to build an on board display for OBDII data in my car.
Elm Electronics has what looks to be a PIC based protocol interface to the OBDII computer.
I have a small video display from a portable DVD player which accepts a composite video signal. Using these with a PICAXE is my initial plan.

I am looking for suggestions on the how to interface to the display.
It's been quite a few years since I have messed with video.
Are CRT controller chips like the 6845 still the way to go?
I've done the obligatory searching but haven't found anything really cool.

I would like graphic capabilities if possible instead of just plain text.

Thanks for any and all suggestions.

 

[papaof2]

The simplest method would be a video overlay board that puts text on the screen.
Six lines of 16 characters each is $35US.
Read through this thread - links on second page:
http://www.picaxeforum.co.uk/showthread.php?t=7934

John

 

[hippy]

I'd recommend the Propeller Chip if you are happy to build it yourself, and you'll have no end of fun if you want to get into bit-banged video. If you don't want the fun then there are pre-built libraries you just need to use. I'm working on creating a a ready to run video driver controlled by PICAXE serial - composite video text display, PAL ( 40x16 or 40x25+ ), NTSC ( 40x13 or 40x25 ), 16 colours - a souped-up AXE033 LCD Controller.

I estimate 20 USD / 20 GBP ( not a typo ) cost.

 

[Brietech]

Are the propeller chips that much more expensive in the UK? Maybe we can work out a swap deal for some high-end picaxes =)

 

[hippy]

@ Brietech : The UK importer / distributer I used has quite high markups, but there is a ProtoBoard ready built for 16 GBP + VAT + P&P which requires five R's a video and a 'from PICAXE' connector to get a PICAXE to TV display working. That is the Value For Money option, works out cheaper than buying the chip, crystal, eeprom, regulators etc. You'll need a PSU or unsolder the 5V regulator and run from any 5V(ish) supply.

The USB programming adapter is considerably more expensive than the Rev-Ed PICAXE download cable. There is an RS232 two transistor interface but not sold by the distributer I used so would have to be built. MAX232 inverter should work so should 74HCxx.

It is nowhere as cheap as a PICAXE solution but is comparable to other video boards. It isn't broadcast quality ( some shimmer / herring bones / moiring ) but perfectly serviceable and a change of crystal might improve things. Its big advantage is that the code can be improved upon and functionality can be added ro changed. Want VT100 or Wyse terminal emulation; just write the code. Want VGA or graphics, then just change the driver. Three more R's and a socket and it's a PICAXE to USB Bridge. Two caps, R's and a jack and it's a stereo sound generator. It can do all these things together.

 

[slurp]

Have you seen these?

http://www.speechchips.com/shop/item.aspx?itemid=5

A low pin count solution with serial communication

If you're thinking of rolling your own solution Maxim have a nice sheet on video basics here:-

http://www.maxim-ic.com/appnotes.cfm/appnote_number/734

and there's an interesting pic controller solution here:-

http://www.rickard.gunee.com/projects/video/pic/howto.php

best regards,
colin

 

[hippy]

The SV2000 looks quite nice and I've done the PICmicro solution with 16F88 but the real problem is limited rows, columns and only monochrome. Minimal footprint and ease of use though. If I wanted a simple life I'd take the SV2000, but I'd much prefer full colour and more text displayed on TV or on a VGA monitor. YMMV as they say.

Additional advantages of a programmable system is a few components turn it into a Video Overlay and it should be feasible to add TeleText/Closed-Captions as well. Very handy to have two screens which can be switched at a push of a button. TeleText allows for as many screens as one can fit in memory.

 

[Rooster]

Perfect, thanks guys.

I just ordered an SV2000. It looks extremely simple to get started with. It has user definable fonts so I think I can make some crude graphic characters for bar graphs or something.

I'll start there and see where it takes me.

Thanks again.

 

[MFB]

low cost video overlay

I use the SX Video OSD Module from Hitt Consulting (www.hittconsulting.com). This 1.5 X 2 inch board accepts serial ASCHII and overlays 8 lines of 24 characters on PAL or NTSC video. This is the low price option, because Hitt also sell a higher perfromance 'prop' based graphics board.