tepples wrote:Optimal at least for light pen use with Zapper-style hit detection would be 15.7 kHz ... at least we can see some ducks die.
Uhm, I am feeling a bit uneasy about that game, I get the idea about shooting enemies because they are ugly, dangerous, or guilty... but shooting cute harmless innocent ducks just for the fun of it - that's about the scariest killing game that I could think of (next to PSX fishing games).
Technically, yeah, the 15.7kHz backlight might work for early lightgun games (ie. those that display a white rectangle at the target location), I guess, for distinguishing between TV and normal light sources, that games check for 15.7kHz light flashes, and/or for no light during vblank? The latter would be more difficult.
Oh, and another unexpected side effect would be classic 15.7 kHz noise. I've just noticed that I am hearing some feeeep sound on my PC's speakers, especially with higher backlight duties in 70%...99% range (and the sound it goes off when using 100%). The PC and TFT screen are sharing the same GND, and also the same 5V supply. Easiest workaround would be to use some higher/inaudible PWM rate like 30kHz.
And I am wondering, what is better for backlights: A constant HIGH duty, or a constant TOTAL duty? At the moment, my PWM output uses constant TOTAL (6.3kHz), and the backlight slider allows to change the HIGH duty from 0% to 100%, one small problem is that 1%..13% are leaving the screen completely black.
Ie. instead of dimming by decreasing the HIGH time, it might be better to maintain some fixed HIGH time, and instead increase the LOW time?
mikejmoffitt wrote:I have a display with one of these controllers, and it's a nice 640x480 one that'll take VGA. I hoped to modify the firmware to have it line double a 15KHz RGB source instead.
The flickering I think is a result of the LCD itself, not the display controller. I am pretty sure a regular progressive scan is sent to the LCD.
Are you sure that you have VGA input... on these AMT630A chips? As far as I know they support composite only (and maybe S-Video, at least on older AMT630's).
The flickering occurs on the floor cells in Magic Floor SNES version. On the other hand, the Magic Floor AMT630A version doesn't flicker. So the TFT seems to be okay, but the displaying the AV signal is somewhat unstable. Not sure what is happening there, the theory about interlace might be wrong, maybe the thing is permanently trying to re-calibrate itself to the incoming signal, or maybe the SNES signal itself is unreliable (gotta check back if the game has similar flicker on a real CRT).
Btw. can somebody recommend an audio amplifier for the two speakers? I have 5V power supply, and the speakers are around 1W each, and it would be nice to some volume regulator that could be driven via PWM, and, some way to force the amplifier to low power standby mode (or automatically having near zero power consumption when receiving "nothing" on the L/R audio inputs).
What I have at home is a TDA1308 Class-AB stereo headphone driver (might be a bit weak, but maybe better than raw unamplified audio), and two mono LM386N-1 amplifiers (which might be more suitable). The TDA and LM's don't have a volume regulator input though.
And the speakers are two "VECO 35KN04" ripped from some old dead notebook. I've somehow managed to find some specs on http://www.veco.com.tw/cgi-bin/product-search.cgi
(despite of 99% broken links at veco.com.tw):
Code: Select all
Model Dimension Impedance Power Rating Fo SPL Frequency Material Material Type
Dia. x Depth +/- 15% Mini-Watts Lowest Normal Range of of Out-looking
Resonant Power SPL-10 db Diaphgram Frame
Frequecy Input/ Hz.
+/- 20% 0.5 meter
Normal Max. db
35KN08 35x16x4.2 8 1000 1500 650 82 400~4000 Cloth ABS Square
So 35KN08 would be 35x16x4.2mm, 8 ohms, and, hmmm, 1000-1500 "mini watts", whatever that is, probably milliwatts.
And mine are 35KN04, which should translate to same size, 4 ohms, and... maybe similar watts.