search

ramapcsx2 / gbs-control

GNU General Public License v3.0
773 stars 110 forks source link

SCART RGB to VGA #161

Open 3r1kd0f opened 3 years ago

3r1kd0f commented 3 years ago

Hello,

I have successfully built the hardware and software to make my NodeMCU and GBS-8200 nicely work with gbs-control. It works well with VGA input.

I then started to build a SCART RGB to VGA as suggested on https://shmups.system11.org/viewtopic.php?f=6&t=35423

It seems the sync isn't working properly:

https://imgur.com/a/JwzRGEQ

I have added a 100ohms resistor between SYNC and GND on the GBS-8200.

Do I need to put extra resistors on LM1881 pin 1 (HSYNC) and pin 3 (VSYNC) ?

How can I measure if the LM1881 is working properly or debug further ?

I have checked the obvious things and all the wiring is OK. I measure 5v between pin 8 (vcc) and pin 4 (gnd).

Any help would be appreciated. (and sorry for posting this here this might not be the best place as not directly connected to gbs-control)

ghost commented 3 years ago

I've been having the same issue, though I'm using composite sync directly. I believe your LM1881 is set up correctly, however something else is preventing the GBS-8200 from correctly displaying the image.

dekkit commented 3 years ago

Can you post pics of your wiring and schematic (the link only showed parts as the pics are gone).

I built a scart adapter for mine with no issues using an lm1881 as well, i believe the main difference from what you posted is adding a 470r in series with the output of the lm1881 (to drop sync levels further). I did not need to add 100r between sync and ground. Note i was powering the gbs and the lm1881 using 5v (not 12v)

I basically used retro rgb's handy sync stripper steps here https://www.retrorgb.com/syncstripperdiy.html

Tested with a few sega consoles (with composite video as the sync source) if that helps.

20210217_222658~2