3.5mm audio/video question

[Omnija]

@ortsac thanks, i would of tested it myself but currently just moved... so my pi's in a box somewhere.

[herb_fargus]

@ortsac I've found with a lot of those 3.5mm to composite I had to swap around the colours in order for it to show proper but may have just been a crappy supplier

[PokeEngineer]

@herb_fargus

Yeah, same with me.

[Capeman]

@herb_fargus @Omnija There are multiple different specs for TRRS 3.5mm to rca cables. The differences in these specs has to do with the placement of the a/v signals and the ground on the rings, tip and sleeve. It's a confusing mess and poorly documented.

The raspberry pi supports the same spec as used by Apple iPods, so any TRRS 3.5mm to RCA designed for ipod or zune will work just fine. The camcorder spec has the same ground location, so switching the AV cables around will usually still work, these appear to be the most common cables found in the bottom of people's random wire boxes.

The cables used in old feature phones will NOT work since the ground is on a different pole location, i don't think it will cause damage to try it, but you'll definitely get some messed up results.

I've attached a diagram showing the differences in how the 4 poles are layed out in various TRRS plugs.

The raspberry pi supports CTIA/APPLE (center) and kinda supports CAMCORDER AV (left) if you switch the red and yellow cables. The OMTP/NOKIA cable spec will simply not work.

[Capeman]

@omnija So an easy test, if you don't want to plug it into your pi, is to short the contacts i labeled below with a multimeter set to continuity (or an LED and a battery) to see if these connect. If they do, then ground is on the second ring and you're in the clear.

[herb_fargus]

@capeman useful info. I guess I just have a bunch of the camcorder type.

[Capeman]

@herb_fargus I have a few of them myself. No idea where they came from, I don't remember knowing anybody with camcorders, haha.

[edmaul69]

@capeman xbox 360 e slim a/v cables are wired correctly as well.

[MrGasS27]

The cable MUST have this pinout, I had to re-solder completely a cable that I have (I re-soldered cables on the 3.5 jack, for precision) and after this job it worked like a charm with my Pi3 :)

[Capeman]

@mrgass27 The camcorder spec also works, due to the ground being on the same pin. For that spec, just switch the audio R (red) and composite video (yellow) and they will work the same. See my diagram above.

The only must not situation is the Nokia (and other feature phone) spec, that one has a conflicting ground location, so it cannot be used.