Re: [uCsimm] Dragonball on TV

From: Raj Kumar (
Date: Sun Jan 07 2001 - 16:02:42 EST

Thanks for the suggestions.

I have considered using the STV5730A from SGS Thompson - basically an On
Screen Display (OSD) chip. The specs are quite reasonable for text-only
display. The BOB-II display modules are quite impressive - although a bit
expensive to use in quantities.

I am more interested in trying to tweak the built-in LCD controller (on the
Dragonball) to display text (or even bit-mapped graphics) on a TV. I am
looking at a typical resolution of 320x240 pixels (pretty much the maximum
you can get on a standard TV with a composite video signal). The idea of
putting the LCD controller into 4bit mode and using a resistor network
sounds good. 16 shades of colour would be good enough for most appications.

I have not worked with the dragonball yet (I have just ordered for the
uCSimm Kit) and I do not know specific details of programming the LCD
Controller. I wonder if it is possible to control/tweak the LCD timing
enough to realize the HSync and VSync pulses. Even if this is possible at
the register level, how difficult will it be to control it from within
uCLinux ? (p.s : I am a hardware engineer - in the process of getting his
feet wet with uClinux)

I have experience working with video (digital and analog). Generating the
required timing using external logic (FPGA) and dual ported SRAM would not
be too difficult - but then its no big deal - there are dedicated
controllers out there that are far more powerful ! The trick is in making
the Dragonball think its driving an LCD while it is actually driving the TV
screen !



----- Original Message -----
From: Micah Dowty <>
To: <>
Sent: Sunday, January 07, 2001 12:01 AM
Subject: Re: [uCsimm] Dragonball on TV

> I've done a bit of TV interfacing with a PIC. Color is tricky, but black
> and white should be relatively easy. I don't know what kind of resolution
> this would give you, but maybe you could try putting the LCD controller in
> 4-bit mode, then connecting a resistor network or cheap DAC to the
> output. A resistor network might be better, so you could tweak the level
> of each possible output.
> In composite NTSC video (I don't know PAL but I would assume it's
> similar) black is at some voltage above zero (0.25V IIRC) shades between
> black and white range between that and 1V, and a sync pulse drops to 0V.
> If you could allocate a sufficient amount of video memory to handle the
> picture itself and the sync pulses, you could get 15-grayscale TV output
> with only a few resistors.
> On Sat, 6 Jan 2001, Raj Kumar wrote:
> > Hi everybody,
> >
> > I am working on a project that requires me to interface a MC68EZ328 to a
standard colour TV. I am planning to use uClinux.
> >
> > Has anyone out there worked with / interfaced a low cost TV/Video
controller to the Dragonball ? The primary objective is to display text
(English) onscreen. Bit mapped graphics would be great ! Colour display
would be even better !!
> >
> > I need to keep costs low. I am looking for a simple / single chip
solution (without extra Video memory etc.)
> >
> > Has anybody tried/thought of tweaking the onboard LCD controller to
generate TV timings ? (HSync/Line Pulse of 15 KHz and VSync/Frame Pulse of
50 Hz) ?
> >
> > Any feedback will help.
> >
> > Raj Kumar
> > Bangalore, India
> >
> >
> --
> >From the command line of Micah Dowty.
> 2 + 2 = 5, for very large values of 2
> This message resent by the list server

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