PIC interface with an old arcade monitor

[Kova]

Hi all,

I have an old arcade games with a CGA (Hsync 15kHz Vsync 60Hz) and EGA (Hsync 25kHz Vsync 60Hz) monitors and I want to interface with a PIC.

The arcade monitors, than a VGA monitors (Hsync 31kHz Vsync 60Hz), work with a different Hsync freq.
The video signals present on the monitor are: R,G,B, Sync, Ground (here you will find the complete pinout of jamma standard: **broken link removed**)

So, this is (a part of) what I would like to do:
I downloaded from here: http://www.pic24.ru/doku.php/en/osa/articles/vga_game the source code, but it ìs written to work with a VGA monitor.
In the vga_game_main.c file there is this code:

    //------------------------------------------------------------------------------
    // Timers
    //------------------------------------------------------------------------------
    
    T2CON = 0x1C;   // post = 4;
    T1CON = 1;
    PR2 = (char)(1.2 * 318/4 - 1);      // 31.8 us

    CCP1CON = 0x0C;         // PWM mode

This is used to generate the 31,469kHz sync.
Which timer register I have to modify to generate a 15.75kHz sync freq?

In the arcade monitor interface there aren't Hsync and Vsync signals but only the Sync signal, so both H/Vsync signals (output from the pic) will be connected together in the same point (P point on the jamma connector).
This connection (H and Vsync connected together) is also used when it connects a PC to an arcade monitor (in this case the Hsync video frequency is forced to work at 15kHz by a dedicated software).

Thanks a lot for any advice.
Bye

 

[Kova]

Hi again,

I would extend my thread with another question that I hope somebody can answer
I drawn this scheme (I know that it is not make enough sense ):


The PIC2 has to control the 2way switches to decide which video signals have to connected to monitor. It has also used to switch ON/OFF the PIC1 (that generate the video signals at 15kHz)
Which type of switches I have to use to switch these video signals?
Is there some impedence issues?
To switch on/off the PIC1, can I use a relay on the VCC line?

Thanks a lot
Best regards

 

[Kova]

Nobody wants to help me ?