JP21 scart compatability

Question

If some one made a video game system with a scart/jp21 port and the system checked and switched outputs between the two types of cables, would that be doable? I apologise before hand at my poorly worded question !

Answer 1

Sure, I don't see why not.

Essentially, you're asking "how do I autodetect a SCART or JP21 sink device?" AFAIK, there is no standard provision for this, but because the connector pinouts are different, you can probably check for continuity between grounds (some grounds are in different positions on the two pinouts).

For example, pin 3 is audio output in SCART but audio ground in JP21, so if you have other pins grounded (and the source doesn't have a completely floating audio section, which would be weird), you could raise a small voltage (through a resistor) on pin 3 (not too much, so as not to damage the audio inputs of a SCART device) and measure the current being sunk. If it's a SCART device, it should be very small, if it's JP21, it should be a fair bit. Based on that measurement, you can then remux all the lines that differ.

However, you may have to do this on several lines, and it might not be foolproof, because some devices may leave several lines N/C. Therefore, a switch to override the setting is probably advisable.