B & W output
Dutch
Posts: 8
Hi, I am currently outputting text only to a small LCD using the TV object. I do not need colour and have tried setting VCFG and VSCL but the timing is out. So does anyone know what would be suitable values for VSCL. I am OK with VCFG, have cleared the CMode bit, also is there something else I am missing. Any help would be appreciated.
Comments
However this is o.k. when you know what you are doing.
(b) You have to tell us something about your monitor.
(c) One can generally calculate the pixelclock from numbr of lines and pixels per line.
What means: "I don't need color?" So don't use it, but there is not much penalty. The picture can become sharper without the chroma signal. Is the monitor able to display color? So try it first with color.
When you have the fourth resistor (audio/chroma) connected to the DAC, unsetting global chroma might not be a very good idea.
All the "colors" you need have to be grayscale (there are around 6 gray colors), the chroma bit in all colors mast be reset.
(d) What does it look like when you use an unchanged TV.SPIN?
Try also to set PAL.
I don't know if anyone did this before, it's not difficult, but tricky...
(1) Clearing just the CMODE flag seems risky, as you do not know what sync or porch operation might trickily rely on 4-color mode....
So we change it for the visible stuff only:
before ":tile" near line 93 add ANDN vcfg, fourcolorbitmask after "djnz x,#:tile 'another tile?" add OR vcfg,fourcolorbitmask obviously define "fourcolorbitmask as LONG |< 28 somewhere As we now need only half of the bytes in a line we devide the columns by 2 Note that we still configure 16 bit tiles; it is too risky to touch the center routines.... This is around line 102, setting the loop counter mov x,_ht 'set horizontal tiles SHR x, #1 ' note _ht must be even(2) Now for VSCL (your question): as we now output 32 bits we have to double frame clocks
this is around line 316:
old: mov hx,_hx 'compute horizontal metrics shl hx, #8 or hx,_hx shl hx, #4 mov hc2x,_ht shl hc2x,#1 new: mov hx, _hx 'compute horizontal metrics shl hx, #7 or hx, _hx shl hx, #5 mov hc2x,_ht Important! Delete this line: shl hc2x, #1 as the lines are now only half as longNote: I did not touch the COLOR vector. You now only need half the vector as the number of EFFECTIVE tiles (not the "configured") is reduced.... This is not very clean... I do not see immediately whether only the first half of the COLOR vector is used or the even entries only... This is something for YOU to fix
Post Edited (deSilva) : 9/4/2007 8:02:43 PM GMT
The version used in those programs always draws in "white" regardless of the current "color" setting. I have an updated version which I am using for another project which supports drawing in both white and black (thus allowing you to "erase" regions of the screen".
In the interest of saving memory, my version does not support lower case text, but that is trivial to add back in.
I have not yet added support for wide pens (i.e. drawing thick lines) or for block fill (the block fill code needs to be rewritten for the memory layout of a 2 bit image, and I have not yet bothered because I haven't needed it).
Works for me[noparse]:)[/noparse]
Rich
The forth resistor is used for anything coming out of the fourth pin
In baseband mode this is the chroma signal when the option "separate chroma" is selected. This is extremely useful and necessary for S-Video. It would have been a good idea on some boards to allow its exclusion from tha DAC by a jumper. Some boards do this, or even sport an S-Video plug.
The problem when setting "separate chroma" is that the chroma signal will sneek in by this path in in unorderly way giving you subtimes sub-optimal color quality, depending on the tolerances of your monitor
Post Edited (deSilva) : 9/5/2007 5:48:31 PM GMT