Amiga-Digital-Video

Add pixel-perfect HDMI output to the Amiga machines.

For all Amiga versions that have a socketed DIP Denise chip and the required physical space inside, a rather small adapter board can be used to extract the digital video signal (12 bit) to a 40-pin connector compatible with the Raspberry Pi Zero. This can then be used with the RGBtoHDMI software to produce a perfect HDMI picture with very low latency (a few milliseconds at most).

Stuff needed

The only hardware needed that can not be bought off-the-shelf is a small adapter board that goes under the Denise chip.

The rest can be directly bought from many electronics retailers:

• Raspberry Pi Zero (any variant)
• Micro SD card (any) and some means to transfer data to it.
• Mini-HDMI adapter or adapter cable (may already come in a set with the Pi)
• Some HDMI extension to reach the outside of the computer case

An optional push button can be added to allow forcing of specific output resolutions and other tweaks. As the device auto-detects the monitor resolution and produces the best possible picture anyway, this is normally not needed.

Software

The Raspberry Pi needs to have a version of the RGBtoHDMI software on its SDCard. A compatible release of the software is available from the RGBtoHDMI repository https://github.com/hoglet67/RGBtoHDMI/releases. Unzip the content of the archive to the root folder of a micro SD card, formatted as FAT32. This card goes into the Rasperry Pi Zero and contains all software needed. Because the adapter board contains a configuration selector, the Amiga profile is already preselected and can be used directly.

Installation - no soldering required

When you are not comfortable with a soldering iron or just don't have one, you can easily obtain a Rasperry Pi Zero with preinstalled pin headers from various vendors. When you use this and don't require the optional menu button (for expert use only), the whole installation is just done by plugging parts together. Depending on how you want to bring the HDMI signal out of the computer case, you may have to cut a hole in the case. Or to keep the case original, you could also bring the cable out through some other opening (like the expansion port), or just do not close the case at all.

Step by step installation instructions

There is also a nice Youtube video series from a user showing the installation process in more detail: https://www.youtube.com/user/brostenen

Compatibility

The first revision of the adapter board works with PAL and NTSC Amigas that have an OCS Denise (8362 variants).The current version of the board (V2) also supports a DIP-48 8373 SuperDenise (sorry, Amiga 600 users), but only as long as one of the OCS screen modes is used (320x256, 320x512 interlaced, 640x256, 640x512 interlaced).

For very early models of the A500 and A2000 as well as all the A1000 models, some additional soldering to the main board is needed to bring the necessary signals to the Denise socket. Refer to https://github.com/c0pperdragon/Amiga-Digital-Video/issues/28 for more details on how this can be done.

Please note that the HDMI signal will not carry any audio. You still need to get the audio signal from the RCA jacks as usual. If you absolutely have to merge the audio signal into HDMI there are dedicated external solutions for that.

The output device needs to support at least 1024 lines because the mod quadruples the screen resolution. So I very much guess an early 720p TV will not work at all. Digital computer monitors normally already have a sufficiently high resolution. Also some monitors may refuse to work with a video signal with 50 frames per second as produced by the PAL Amiga variants. In such a case you can force the upscaler to 60 frames per second mode by pressing the menu button during power-up. If you have not installed the button, you can as well just semi-permanently put a jumper link on the button contacts instead. When you force 60 frames in such a way, you will experience screen-tearing or jumpy scrolling in games or demos, so this fall-back should only be used if it would not work at all otherwise.

Small adapter variant

For installation in an A600 or for other constrained installation, I have designed a generic adapter. Instead of being a plug-and-play solution, this board needs substantial soldering of individual wires. Gerber files, schematics and BOM are available at https://github.com/hoglet67/RGBtoHDMI/tree/master/kicad_AmigaAdapter/Small .

Use this issue thread for discussions on this special topic: https://github.com/c0pperdragon/Amiga-Digital-Video/issues/22

By accident I have ordered a large quantity of PCBs for these small adapters which I absolutely do not need. So if you want some bare PCBs really cheap, please drop me a mail. I could send you a simple envelope with 2 PCBs for €3.

Big box variant

Specifically for the use with the Amiga 2000 and Amiga 3000, user Bloodmosher has designed a board to go into the video slot of these machines. He also intends to sell finished boards to interested users. For more details check https://github.com/Bloodmosher/Amiga-VideoSlot-RGBtoHDMI

Build your own adapter board or get it ready-made

The board schematics and PCB design is open-source and part of the RGBtoHDMI project If you are not confident to solder parts with 0.65mm pin pitch, you can contact me via (reinhard.grafl (at) aon.at) to get a completed board. I would give these away for €29 plus shipping. For availability of such boards, please check this page: https://github.com/c0pperdragon/Amiga-Digital-Video/issues/13