Running RetroPie 👍
Running RetroPie on CRT 😃
Running RetroPie on CRT with RGB 😍
VGA to RGB Scart cable
The RGB signals in VGA are compatible with the Scart RGB signals so they can be connect directly but the HSYNC and VSYNC must be converted to CSYNC. I used the circuit below for the conversion. The idea is taken from nexusuk.org that is no longer available but it can be accessed from archive.org.
To make the TV switch to RGB mode 5 volt should be feed via a 100 ohm resistor to pin 16 in the Scart connector. Normaly there is 5 volt output from a VGA port but this adapter don't provide that. Instead I came up with a solution to tap it from HSYNC. It's a bit ugly but it works fine for my setup. Another solution would be to connect a USB cable to the Raspberry Pi to get 5 Volts.
Change video mode for the HDMI port
To make it work we also need to edit the file config.txt in the boot partition.
1. Add these line to make text in dialogs and the console a suitable size.
2. Add these line to output the correct signal for Scart RGB. Make sure that you don't have other video config line enabled!
#hdmi_cvt=336 249 60 1 0 0 0
hdmi_cvt=320 312 50 1 0 0 0
You may want to adjust the numbers a bit for best result. For more details check this forum post
Enable audio from the 3.5mm Jack.
The VGA adapter did not have any audio output so I used the 3.5mm jack on the Raspberry Pi to feed audio in to the Scart connector. Run this command in a terminal to enable it:
Select: Advanced Options-> Audio -> Force 3.5mm