How to attach a SCART connector to the iStar Mini HD

VGA Port

The iStar Mini HD outputs YPbPr and RGBHV over the VGA Connector. Its been said you switch between the two in the menu.

The Menu setting is called “VGA Mode”.

When set to ON you get an RGBHV signal. With this set to OFF your outputting YPbPr which is clearly not a VGA signal type.

cimg1402.jpg “These statements were made on a forum and this what I'm going on to build my SCART/VGA cable”.

Enabling the SCART option in the settings menu makes the PCH output RGB on the component pins.
Thats great if you have a Popcorn Hour, How come the iStar FIRMWARE does not have this option?
This was in the 14-Mar-08 Firmware.


From the iStar Mini HD website they indicate that an optional cable can be supplied, however I'm going to build my own so that I can run my SDTV using component instead of composite.

I suspect the PCH has the same issue as the iStarHD so this is probably the cable I need to make, with a slight variation for the D-Shell VGA connector that the iStar has vs the 3 component RCA sockets that PCH has.

Questions:

  • Can I use the HSync/CSync (pin 13) signal from the VGA or do I need to also tap the Composite RCA ?
  • Is pin 9 supplied with +5v? This can be used to signal RGB in the SCART. NO

Pulling apart the iStar and testing which pins are being used we discover that only 6 pins are connected internally.

vga.jpg VGA connector pinout:

Pin Description J2 Connector
1 Red Video 3
2 Green Video 1
3 Blue Video 2
10 SGND (Sync Ground) 4
13 HSync (or Composite) 5
14 VSync 6

With the Key space on the right of the J2 (internal VGA connector). The pin mapping is as follows:

    +----+
    | 1  |
    | 2  |
    | 3
    | 4
    | 5  |
    | 6  |
    +----+

Wiring pin out for SCART

Preliminary wiring diagram

cimg1366.jpg cimg1367-web.jpg

Test results 25-May-08: The picture that appears on the screen is right shifted to about the midway point of the screen. The colours are wrong and there appears a distinct green'ish hue to everything.

    Composite RCA  Scart Male (plug)
    --------------------------
    Composite          20  Composite video input
    GND                17  Composite video input ground

Its almost as if the Composite Sync signal isn't the right source to lock the RGB signal onto. Next thing to try is the HSYNC signal from the VGA as the sync source as this might be a CSync signal.

But if we didn't have sync signal the image wouldn't be stable?

Also tried - This didn't even give a stable picture.

    VGA         Scart Male (plug)
    --------------------------
    13 CSync          20  Composite video input
    10 GND            17  Composite video input ground

Perhaps a YPbPr signal is being sent down the VGA port? Instead of RGB. Clearly if this is happening then iStar have an issue with their firmware and the VGA menu option.

The rest of the wiring seems to be ok.

iStar VGA      Scart male (plug)
-------------------------
 1 Red             15
10 SGND            13
 2 Green           11
10 SGND             9
 3 Blue             7
10 SGND             5

Audio RCA      Scart male (plug)
-----------------------------------
Audio Right         2
Audio Ground        4
Audio Left          6

Power connector                                 Scart
------------------------------------------------------
Centre pin (12V) -+-> 330 Ohm -+-> 200 Ohm ------> Pin 16 blanking signal pin
                  |            |            1.48v       
                  |      2     | 6.5v                    
                  |      o     |                     
                  +----o   o---+                     
                      1   / 3                         
                         o                           
                         | 3-way switch               
                         +--------------------> Pin 8 (Function select aka Switch)
                                         
Outer ring (Gnd) -----------------------------> Pin 18 (RGB Control / Function select ground)

Pin 8, the switch signal pin, carries a low frequency (less than 50 Hz) signal from the source that indicates the type of video present.

  0v–2v means no signal, or internal bypass
  4.5v–7v (nominal 6v) means a widescreen (16:9) signal
  9.5v–12v (nominal 12v) means a normal (4:3) signal 

Pin 16, the blanking signal pin, carries a signal from the source that indicates that the signal is either RGB or composite.

  0v–0.4v means composite.
  1v–3v  (nominal 1v) means RGB only. 

I believe that the iStar mini HD outputs YUV COMPONENT video and not an RGB signal. This means we probably need a conversion circuit.

To be strictly accurate RGB is a component signal, however in reality the day to day terminology is different. Component refers to YPbPr (USA,AU) signals and RGB is usually UK Scart RGB.

In Conclusion

It looks like I spent the day building and testing a cable and just wasted my time unless of course this VGA menu option magically appears one day and then I'll be ready !

SCART connectors used with many European video equipments are designed to carry composite video and RGB video signals. If the equipment which outputs picture outputs RGB-signal, it will put the RGB signal on the RGB pins and a complete composite video signal at the same time.

  • If the receiving equipment uses RGB, it will take picture from RGB pins and sync from the composite video pin.
  • If the receiving equipment understands only composite video, it will use the picture in it.

Reference designs for a RGBHV to SCART cable.