In addition, many other vintage computers like the Commodore 128, have a 9-pin D-Sub connector for 80-column mode. For monochrome, make sure no sub-profile is selected as it may cause the card to needlessly try to resync. Many video modes use different scan rates, and the sub-profile will allow the card to automatically switch to any other scan rate for that mode. The board has an on-screen menu which will allow you to select the profile, and sub-profile for the video mode you wish to use. Most clone or vintage PCs which predate VGA will use this connector for monochrome (MDA), Hercules, CGA or EGA. Once the device is connected to your HDMI monitor and power, you can connect a straight through 9-pin D-Sub cable directly to any standard TTL source. Ideally, you need to supply approximately 1100ma 5v, but it does seem to work on as little as 500ma. Lastly is a standard mini-USB cable to connect power to the board. We also include a 4GB microSD card with the RGBtoHDMI operating system preinstalled and ready to go. The Pi uses a mini-HDMI connector, so we include an adapter to allow connection to a standard HDMI cable. It comes with feet to keep it from sitting directly on your desk. This kit includes the RGBtoHDMI PCB with the needed Raspberry Pi Zero attached. We also used a 4-layer PCB in this design to allow for a proper ground plane and the best noise rejection possible. We integrated IanB’s 6-bit TTL buffer which will buffer the incoming signal to ensure integrity and some protection for the programmable logic IC. In addition, we designed the device to be a little more desk friendly to make it easy to use with your vintage system collection. This does limit the full capability of the device, but it will also make connections easy for a vast majority of use cases. We immediately fell in love with this board and decided we wanted to make our own, but what would be best to support? Making an all-in-one board really did not seem viable so, in the end we decided the best approach would be to support a 9-pin D-Sub video cable primarily for MDA, CGA and EGA signals. The original design is open enough to allow adaptation of many different video sources, but it does leave the user to make cables for each situation. It uses a Raspberry Pi Zero along with a programmable logic IC to rapidly convert each video frame with amazing clarity. The purpose of the RGBtoHDMI is to convert many different TTL and analog video signals from vintage systems to a modern HDMI or DVI compatible output. The RGBtoHDMI is an excellent open project created by Hoglet67 (David Banks) and IanB (Ian Bradbury).
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