Sam440ep and 8" touchscreen - no display

hello 'migans

Yesterday night i tried to plug my 8" Hami TFT touchscreen to my Sam440. I was surprised to see that it simply doesn't work. I plugged it through the DVI/VGA adapter but i have no display (uboot/OS4). This screen worked on every machine i tried it with (PC, PowerMac, MacBookPro, Efika, Pegasos, amiga 4000 (with scandoubler)...) but won't work with Sam !!

any idea why ???

Of course i'm not refering to the touchscreen features, i know there is no driver for it (or not public) but i simply can't display anything with it.

here's the screen :

@SoundSquare

What you getting, no signal? It's got to be screenmode related surely?

Rude!

@SoundSquare

Maybe screen refresh rate is not correct, or your screen does't support uboot resolution?

well, to answer both of you :

it can't be a matter of screenmode on OS4 as it doesn't even display uboot. Anyway i changed the screenmode settings before unplugging my regular screen to try this one. I still have no signal.

I don't see why it wouldn't support uboot resolution if it can support any other bios/firmware (pc, mac, amiga, openfirmware from pegasos and efika).what would make uboot different ? it is supposed to be a resolution that can be handled by any screen.

by the way, for those who would be interested, this little touchscreen works fine with a scandoubler on an classic amiga, it displays AGA nicely.

@SoundSquare

Hmm yes, no uboot is a little bizarre so defo not screenmode related as you say.

Anyone else got any ideas?

Rude!

Doesn't U-Boot default to 1024x768@75Hz or something?

Try changing the screenmode in Workbench to 640x480@60Hz, then reboot with this screen and wait until it (should) display Workbench and see if that works.

Or well, just check the specs...?

@SoundSquare

It is probably down to your DVI-VGA adaptor on the SAM 440.
These dongles use the DVI-A (DVI Analog) pins C1-C5, which provide analogue RGB and horizontal or line sync.

A quick search on ebay for that monitor reveals the following:

Video and Synchronizing signal:
- Video Frequence: analog level
- Line synchronization: TTL positive logic/negative logic
- Frame synchronization: TTL positive logic/negative logic
- Pixel frequence: 120MHz (Maximum)
- Display color: Subject to VGA card
- Video signal and input: 0.7Vpp
- AV, TV and PC (3 in 1) display
- Horizontal frequence: 68KHz (Maximum)
- Frame frequency: 75KHz (Maximum)

The important point here is that it need a frame synchronisation signal, which is not provided by the DVI-A connection.

The Amiga provides Horizontal/Line and Vertical/Frame syncs and a composite sync.

Unless you have a VGA connector on your graphics card, I can not see a solution.

Ian

@Stedy

"Frame" == "Vertical"

@Stedy

Quote:
The Sam board has a header (J25) which can provide a VGA signal. The pinout is documented in the manual.


Best regards,

Niels

@nbache

Hi Niels

The manual also talks about LVDS (J26), is that socket actually mounted on the board?

Ok, checked various photos and there seems to be a socket.