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Saturday, August 31, 2013

Smartphone/tablets audio connectors

One of the few things really annoying is when manufactures decide to don't follow a single standard for the connectors of their products.
I have around some smartphones and there are differences on the audio (3.5 mm) connector.
These differences creates problems with some accessories.

For example I bought a very nice desktop phone stand from Aptiva, but I soon discovered that it is incompatible with my Sony Ericsson Xperia.
The same for a Hype Retro Walkie Talkie handset I wanted to use to enhance the Zello experience.
On the Sony is not working at all, on the Samsung tablet works in part (see the note on the bottom of this article).

So there are differences about the connection of the 3.5 mm audio port on these devices.
This article is trying to document the pinout of different phones/tablet and giving information about this problem and how to solve it.

Introduction


The typical 3.5 mm jack is divided in different areas :
  • Sleeve
    The part of the connector close to the handler, the cover.
  • Ring
    The part of the connector separated by a insulator ring
  • Tip
    The far part of the connector, the "point"
There are many different types of jack.
In the figure below, there is an explanation of the main parts of such connector.
This type of  jack is called TRRS  (Tip/Ring/Ring/Sleeve) and it become the "standard" for smartphones.

The most known type of jack is the one used to connect the standard stereo headset.
This type of jack is called TRS, from the initials of the connections :
Tip - Ring - Sleeve


CTIA Audio jack


CTIA defined an audio connector.
It is a TRRS  :
  • (sleeve) Microphone input
  • (ring) Ground (common)
  • (ring) Right Audio out
  • (tip) Left Audio out

iPhone 4S



Many audio accessories are labeled as iPhone compatible.
This means that the majority of the audio accessories found on the market follow the Apple standard for the 3.5 mm audio connector.
The iPhone/iPad audio jack follows the specifications defined by CTIA.



So every accessories that declare to be iPhone compatible has the pinout shown above.

OMTP audio jack


Android, as general rule, seems follow a standard defined by a group called OMTP.
However different manufacturers choose to follow the CTIA, others didn't.
The main difference between the CTIA and  OMTP is switching the place from Ground and the Mic.
So each Android smartPhone or Android  tablet can have different audio jack pinouts. That's very very bad.
This is the OMTP connector :


So let see different brands what offers.
Keep in mind that usually models of the same brand uses the same pinout, but it could be different !
So never assume.

Sony Ericsson Xperia LT18a


OMTP standard

In order to use Apple iPhone standard accessories, is necessary to use a converter.
It is possible to search for CTIA<--->OMTP conversion cable or it is relatively easy to build one.

Samsung Galaxy Tablet 7" GT-3113


CTIA standard

Samsung SPH-M910


CTIA standard


FriendlyArm Tiny210 SDK


This OEM board can run Android 4.0.3.
It has a TRS jack for the audio output and a TS jack for the audio input.





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