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I have some devices with an RS232-connection (e.g. a beamer, a TTL-to-RS232-adapter for my NanoPI R1 described here, etc). No i have found a RS232 to VGA adapter: enter image description here

Now i wonder, if I would have this adapter-cable and would connect it to my NanoPI and plugin the right-plug in a VGA-monitor: What would I actually see? Would I really see the screen of the NanoPI (or the screen-output of whatever device which is connected)?

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if I would have this adapter-cable and would connect it to my NanoPI and plugin the right-plug in a VGA-monitor: What would I actually see?

Smoke?

I feel that cable is very unlikely to contain the circuitry needed to synthesize any kind of useful VGA graphics signal from character data arriving from a serial port.

That's a male DE-9 to male DE-15 cable. According to Wikipedia as well as being used for RS232, the DE-9 was also used for

video display output such as MDA, Hercules, CGA, or EGA (rarely VGA or others). Even though these all use the same DE9 connector, the displays cannot all be interchanged and monitors or video interfaces may be damaged if connected to an incompatible device using the same connector.

So this cable almost certainly isn't something you should buy.

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  • Better: magic smoke. :)
    – Kamil Maciorowski
    May 2, 2020 at 14:37
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    My guess: that DB9 to DB15 cable is a EGA to VGA cable to display EGA on a VGA monitor that can handle 15Khz horizontal frequency. (VGA is 31 KHz and EGA 15, but back in the day there where monitors that could also do 15KHz for compatibility with TV, and 1980 home computers, like the Atari ST and Commodore Amiga.) I actually have a Princeton 1400 for use with my old Amigas that can do that. EGA works but the colors look awful, which is to be expected as EGA used TTL on/of for RGB. These cables usually have resistors soldered in the DB9 plug to (sort of) match voltage levels to VGA.
    – Tonny
    May 2, 2020 at 14:47

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