1chip msx RGB cable

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Par vanfanel

Champion (446)

Portrait de vanfanel

23-08-2009, 14:14

Hello there!

Today I've been busy building an VGA-SCART cable for my OCM (the Altera DE1 with CARO & HRA! core).
I've followed the instructions here:

www.idiots.org.uk/vga_rgb_scart/images/pinout.gif

www.idiots.org.uk/vga_rgb_scart/images/cable_wiring.gif

but my LCD and CRT TV's just display some white screen with black lines. I've OF COURSE configured the OCM to output at 15HZ mode. Shouldn't that scheme work?

Thanks!!

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Par Devcon

Resident (41)

Portrait de Devcon

27-08-2009, 18:38

No one? If that cable works i'm also interested on making it for my Altera Smile

Par Pac

Scribe (6645)

Portrait de Pac

27-08-2009, 22:17

I made mine with the next schematic and it works fine:

VGA ------ SCART

1 --------- 15
2 --------- 11
3 --------- 7
13 --------- 20
14 --------- 6
10 --------- 17
9 --------- 16

Par cax

Prophet (3737)

Portrait de cax

27-08-2009, 23:51

As I see it,

1,2,3,10,13 VGA pins are connected in the same way in both vanfanel's and EVPON's cables, but

vanfanel also has 6->13, 7->9, 8->5 connections, and instead of those three EVPON has just the following two: 14->6 and 9->16

Par vanfanel

Champion (446)

Portrait de vanfanel

29-08-2009, 13:40

Damn, I just can't make it work! I am useless at soldering because I've got souch a BAD pulse...
Do you know where can I buy a cable like this, already made and ready for use?

Par Repair-Bas

Paragon (1149)

Portrait de Repair-Bas

30-08-2009, 19:48

www.bas-ditta.info

Lots of different cables for msx

Par vanfanel

Champion (446)

Portrait de vanfanel

11-08-2012, 15:43

After buying a cable from www.bas-ditta.info and finding out this cable wouln't work with my Altera DE1, I'm again trying to make my own VGA-SCART cable.

I did EXACTLY the connections mentioned by PAC, but the cable doesn't work. So, please, could you guys test it or give me proper schematics for Altera DE1 VGA-SCART cable?

Par RetroTechie

Paragon (1563)

Portrait de RetroTechie

11-08-2012, 19:50

Possibly your TV('s?) needs some 12V on pin 8 (function switch). According to a doc I have here, that selects 4:3 aspect ratio, IIRC older TV's may use/need this to select the SCART as input source. If you expected the TV to produce an image when switching on your OCM: try manually selecting the input source. SCART pin 16 has a related function (fast blanking) but uses lower voltage for the signal (1-3V), you might want to check what your DE1 board does with this pin.

Btw: have you checked the OCM gives proper image on a VGA screen? (with the OCM configured for that, of course)

Par Mafcase

Master (255)

Portrait de Mafcase

11-08-2012, 20:23

Par vanfanel

Champion (446)

Portrait de vanfanel

11-08-2012, 21:11

@RetroTechie: I tried 2 different new LCD tvs: Samsung and Toshiba.
Same result on both: white image where white letters of MSX-DOS can be read if I get VERY next to the screen. Maybe this could be a hint on the problem but I don't know much about analog image cables Sad

Of course this Altera DE1 MSX produces a good image on VGA Smile

@Mafcase: I tried those, too. Look at the post at my initial post.

I need someone who has done a WORKING, tested cable for Altera DE1 MSX, please...

Par caro

Champion (512)

Portrait de caro

14-08-2012, 11:43

The main difference Connectors VGA in OCM and DE0, DE1 is on the pin 9 VGA
is connected to the OCM +5 V. This signal is fed to the 16 contact SCART
(BLANK), which switches the TV to RGB-mode. In DE1 and DE0 pin 9 VGA
is not used, so even if we connect it with the 16th pin SRART,
the TV remains in the TV-mode.
There are two solutions to this problem:
1) Connect the 16th SCART contact with the 20th (CSYNC).
In most cases it helps, but sometimes due to the fact that the input
BLANK is low input impedance (75 ohms), the level CSYNC falls so low
that it leads to unstable operation of the monitor.
2) Connect the pin 9 VGA on the boards DE0 and DE1 to +5V
(can be via a resistor of 75-100 ohms).
The cable connection to provide contact 9 VGA with a contact 16 SCART.
I did so.

----------------
VGA ------ SCART
----------------
1 ---- RED ----- 15
2 ---- GREEN ---- 11
3 ---- BLUE ----- 7
13 --- CSYNC ------ 20 (+16 for 1 variant)
14 --- SOUND ------ 6 (0.1 uF -> GND)
6,7,8,10 --- GND ------ 17,4,7,8,10
9 ---- BLANK ----- 16

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